METHOD FOR THE SYNTHESIS OF ISOCYANATES

Abstract

A method for the preparation of isocyanates in which: (i) a first organosilicon compound having at least one silicon atom Si.sup.1 and a unit of formula G-I bound thereto

##STR00001##

is converted to a third organosilicon compound having a unit of formula G-II

##STR00002##

by silylation of the NH group of the unit of formula G-I with a second organosilicon compound having one silicon atom Si.sup.2; and (ii) the third organosilicon compound is reacted to an isocyanate by thermolysis, whereby the unit of formula G-II is converted to an isocyanate group.

Claims

1-15. (canceled)

16. A method for the preparation of isocyanates, wherein (i) a first organosilicon compound having at least one silicon atom Si.sup.1 and a unit of formula G-I bound thereto ##STR00056## is converted to a third organosilicon compound having a unit of formula G-II ##STR00057## by silylation of the NH group of the unit of formula G-I with a second organosilicon compound having one silicon atom Si.sup.2; and (ii) the third organosilicon compound is reacted to an isocyanate by thermolysis, whereby the unit of formula G-II is converted to an isocyanate group.

17. The method according to claim 16, wherein the first organosilicon compound is a compound of general formula II ##STR00058## wherein A.sup.1 is R.sup.1 or a group of general formula G-III: ##STR00059## R.sup.1 is a substituted or unsubstituted, aliphatic or aromatic group; R.sup.2 at each occurrence each independently is selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl group with 1 to 12 carbon atoms and a substituted or unsubstituted aryl group, with the proviso that at least one residue R.sup.2 which is not hydrogen is bound to each silicon atom Si.sup.1; and Z is a substituted or unsubstituted, aliphatic or aromatic group; the second organosilicon compound is a compound of general formula III ##STR00060## wherein X is selected from the group consisting of a halogen, —CN, —OCN, —SCN, —N.sub.3, a sulphonate, a carbamate, —O—R.sup.4, —NR.sup.7R.sup.8 or an N-heterocycle; R.sup.3 at each occurrence each independently is selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl group with 1 to 12 carbon atoms and a substituted or unsubstituted aryl group, with the proviso that at least one residue R.sup.2 which is not hydrogen is bound to each silicon atom Si.sup.2; R.sup.4 is —C(O)R.sup.9 or a group of general formula G-VI ##STR00061## R.sup.5 at each occurrence each independently is a substituted or unsubstituted alkyl group with 1 to 12 carbon atoms; R.sup.6 is a substituted or unsubstituted alkyl group with 1 to 12 carbon atoms; R.sup.7 and R.sup.8 each independently are —C(O)R.sup.9 or a substituted or unsubstituted alkyl group with 1 to 12 carbon atoms; and R.sup.9 is a substituted or unsubstituted alkyl group with 1 to 12 carbon atoms; and the third organosilicon compound is a compound of general formula IV ##STR00062## wherein A.sup.2 is R.sup.1 or a group of general formula G-IV: ##STR00063## R.sup.2 at each occurrence and Z have the meanings given in connection with the compound of general formula II; and R.sup.3 at each occurrence has the meanings given in connection with the compound of general formula III; wherein the compound of general formula II is reacted with the compound of general formula III to the compound of general formula IV and the compound of general formula IV is reacted to an isocyanate compound of general formula I
A.sup.3—N═C═O   (formula I), wherein A.sup.3 is R.sup.1 or a group of formula G-V: ##STR00064## R.sup.1 and Z have the meanings given in connection with the compound of general formula II; by thermolysis.

18. The method according to claim 17, wherein R.sup.1 in the compounds of general formula I, II and IV is selected from the group consisting of a substituted or unsubstituted alkyl group with 1 to 18 carbon atoms, a substituted or unsubstituted heteroalkyl group with 1 to 18 carbon atoms, a substituted or unsubstituted alkenyl group with 1 to 18 carbon atoms, a substituted or unsubstituted alkynyl group with 1 to 18 carbon atoms, a substituted or unsubstituted aryl group and a substituted or unsubstituted heteroaryl group.

19. The method according to claim 17, wherein R.sup.1 in the compounds of general formula I, II and IV is selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, and phenyl.

20. The method according to claim 17, wherein Z in the compounds of general formula I, II and IV is selected from the group consisting of a substituted or unsubstituted alkylene group with 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted phenylene-bisalkylene group in which each alkylene group at each occurrence each independently is an alkylene group with 1 to 12 carbon atoms.

21. The method according to claim 17, wherein X in the compound of general formula III is selected from the group consisting of chlorine, a toluene sulphonic acid ester group, a methyl sulphonic acid ester group, and a trifluoromethyl sulphonic acid ester group.

22. A compound according to claim 17, wherein R.sup.3 at each occurrence in the compounds of general formula III and IV each independently is a substituted or unsubstituted alkyl group with 1 to 6 carbon atoms or a substituted or unsubstituted phenyl group.

23. The compound according to claim 17, wherein all of R.sup.2 in the compounds of general formula I, II and IV each are methyl groups and/or all of R.sup.3 in the compounds of general formula III and IV each are a methyl group.

24. The method according to claim 17, wherein the silylation is carried out at a temperature of 0 to 50° C.

25. The method according to claim 17, wherein the silylation is carried out in a non-polar organic solvent in the presence of an auxiliary base.

26. The method according to claim 17, wherein the thermolysis is carried out at a temperature of 150 to 400° C.

27. The method according to claim 17, wherein the thermolysis is carried out using a temperature profile comprising two or more temperature stages, wherein each temperature stage is applied for a given time period and each of the applied temperature stages can be above the previously applied temperature range by 20 to 80° C.

28. The method according to claim 27, wherein the given period of time is between 1 min and 2 hrs.

29. The method according to claim 17, wherein the thermolysis is carried out in the presence of an inert gas.

30. A method for the preparation of an isocyanate compound of general formula I
A.sup.3—N═C═O   (formula I), wherein A.sup.3 is R.sup.1 or a group of formula G-V: ##STR00065## R.sup.1 and Z have the meanings given in connection with the compound of general formula II, said method comprising silylating a compound of general formula II ##STR00066## wherein A.sup.1 is R.sup.1 or a group of general formula G-III: ##STR00067## R.sup.1 is a substituted or unsubstituted, aliphatic or aromatic group; R.sup.2 at each occurrence each independently is selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl group with 1 to 12 carbon atoms and a substituted or unsubstituted aryl group, with the proviso that at least one residue R.sup.2 which is not hydrogen is bound to each silicon atom Si.sup.1; Z is a substituted or unsubstituted, aliphatic or aromatic group.

Description

Example 1

Synthesis of Phenylisocyanate (11)

[0133] Phenylisocyanate (compound 11) was prepared according to the methods shown in scheme 11. Phenylisocyanate is an example of an aromatic monoisocyanate.

Stage 1: Synthesis of Aminosilane

[0134] First, 4.28 g (46.00 mmol) of aniline were provided together with 5.10 g (50.50 mmol) of triethylamine in 100 ml of n-pentane. 5.12 g (47.16 mmol) of trimethylchlorosilane are added under stirring in an ice bath via a dropping funnel. Upon adding the silane dropwise formation of a white solid as well as the development of white smoke could be observed. After the chlorosilane was completely added, the mixture was heated to room temperature and stirred for 24 hours. After the white solid has been removed by filtration and the solvent has been removed under reduced pressure, 7.13 g (43.14 mmol) of N-trimethylsilylaniline could be obtained as a clear, colorless liquid. The yield is 94%. The purity of the product was confirmed by NMR spectroscopy.

[0135] .sup.1H-NMR (400 MHz, C.sub.6D.sub.6, δ [ppm]): 7.08-6.43 (m, 5H, ArH), 3.46 (s, 1H, NH), 0.15 (s, 9H, SiMe3). .sup.13C-NMR (101 MHz, C.sub.6D.sub.6, δ [ppm]): 148.1 (ArC), 129.6 (ArCH), 117.9 (ArCH), 116.7 (ArCH), 0.2 (SiMe3). .sup.29Si-NMR (79 MHz, C.sub.6D.sub.6, δ [ppm]): 2.1.

Stage 2: CO.SUB.2 .Insertion

[0136] 7.56 g (45.7 mmol) of N-trimethylsilylaniline were mixed with 20 ml of dry tetrahydrofuran (THF) and filled into a large autoclave under inert conditions. The autoclave was pressurized with a CO.sub.2 excess pressure of 8 bar and allowed to stand under these conditions for 24 hours. The pressure was periodically controlled. After the reaction time has expired the clear, pale yellow reaction mixture was inert transferred to a Schlenk vessel. After a few minutes formation of colorless crystal needles could be observed. The solvent was removed under reduced pressure and the white solid obtained was dried in vacuum for 3 hours. In this way, 8.62 g (41.17 mmol) of N-phenyl-O-trimethylsilyl-carbamate could be obtained in a yield of 90%. The identity and purity of the target compound were confirmed by NMR spectroscopy.

[0137] .sup.1H-NMR (400 MHz, THF-d8, δ [ppm]): 8.64 (s, 1H, NH), 7.46-6.92 (m, 5H, ArH), 0.30 (s, 9H, SiMe3). .sup.13C-NMR (101 MHz, THF-d8, δ [ppm]): 153.0 (CO), 140.8 (ArC), 129.4 (ArCH), 123.1 (ArCH), 118.9 (ArCH), 0.1 (SiMe3). .sup.29Si-NMR (79 MHz, THF-d8, δ [ppm]): 22.2. Elemental analysis: calculated N 6.69%, C 57.38%, H 7.22%; measured N 6.79%, C 57.14%, H 7.053%.

Stage 3: Silylation

[0138] 6.87 g (32.82 mmol) of N-phenyl-O-trimethylsilyl-carbamate were dissolved in 100 ml of n-pentane together with 3.40 g (33.60 mmol) of triethylamine. The mixture was stirred in the ice bath. 7.28 g (32.76 mmol) of trimethylsilyltriflate were added dropwise via a dropping funnel. Formation of a flake-like second phase could be observed. Subsequently, the mixture was heated to room temperature and stirred at this temperature for 2 hours. The second phase formed was congealed in a cold mixture of dry ice and isopropanol and the supernatant solution was decanted off. The solvent was removed under reduced pressure, whereby precipitation of a white solid could be observed. The solid was dried in vacuum for 2 hours. In this way, 7.69 g (27.32 mmol) of N,O-bis(trimethylsilyl)-N-phenyl-carbamate (1) could be obtained in a yield of 83%. The identity and purity of the target product were confirmed by NMR spectroscopy and single-crystal X-ray analysis.

[0139] .sup.1H-NMR (400 MHz, CDCl.sub.3, δ [ppm]): 7.11-6.84 (m, 5H, ArH), 0.12 (s, 9H, SiMe3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 157.1 (CO), 141.6 (ArC), 128.7 (ArCH), 126.5 (ArCH), 119.5-116.1 (ArCH), 0.7 (SiMe3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 23.4, 10.7. Elemental analysis: calculated N 4.98%, C 55.47%, H 8.24%; measured N 5.07%, C 55.01%, H 8.215%.

Stage 4: Thermolysis

[0140] A few grams of N,O-bis(trimethylsilyl)-N-phenyl-carbamate (1) were filled into the still pot of the kugelrohr distillation apparatus under inert conditions. The still pot and the middle pot were put into the heating chamber (tubular furnace), while the outer pot was cooled in the water bath. A temperature profile was run at a rotation of 20 rotations per minutes (rpm). The furnace was heated to 170° C. for 30 minutes, subsequently the temperature was increased to 200° C. for another 30 minutes, and finally heated to 230° C. also for 30 min. After the solid used was melted accumulation of colorless liquid both in the middle and in the outer pot could be observed. After the reaction time has expired, the pots were cooled to room temperature and inert transferred to Schlenk vessels. The composition was analyzed by NMR spectroscopy. While in the middle pot there was still found undecomposed carbamate, in the .sup.29Si-NMR spectrum of the outer pot only the presence of hexamethyldisiloxane was shown. These results are confirmed by the .sup.13C-NMR spectra. In addition, in the .sup.13C-NMR spectra of the middle and outer pots a signal at 134.0 ppm each was shown which can clearly assigned to the phenyl isocyanate. While in the middle pot a variety of other signals is indicative of a mixture of substances of various species, only the isocyanate together with hexamethyldisiloxane is found in the sample of the outer pot (.sup.13C: δ=2.0 ppm). Further, presence of the isocyanate was rechecked by IR-ATR spectroscopy. Again, the isocyanate band at 2258 cm.sup.−1 was clearly identified. Comparing both analyses with a commercially available sample of the phenylisocyanate provided exact matches.

Example 2

[0141] Synthesis of n-Octyl-Isocyanate (12)

[0142] n-Octyl-isocyanate (compound 12) was prepared according to the method shown in scheme 11. n-Octyl-isocyanate is an example of an aliphatic monoisocyanate.

Stage 1: Synthesis of Aminosilane

[0143] First, 6.02 g (46.56 mmol) of n-octylamine were provided together with 4.79 g (47.31 mmol) of triethylamine in 100 ml of diethyl ether. 5.04 g (46.39 mmol) of trimethyl chlorosilane were added under stirring in the ice bath via a dropping funnel. When adding the silane dropwise formation of a white solid and development of white smoke was observed. Subsequently, the mixture was heated to room temperature and stirred for 24 hours. After having removed the white solid by filtration and the solvents under reduced pressure, 8.11 g (40.24 mmol) of N-trimethylsilyl-n-octylamine were obtained as a clear, colorless liquid in a yield of 87%. Purity of the product was confirmed by NMR spectroscopy.

[0144] .sup.1H-NMR (400 MHz, CDCl.sub.3, δ [ppm]): 2.81 (t, 2H, CH.sub.2), 1.50-1.40 (m, 12H, CH.sub.2), 1.01 (t, 3H, CH.sub.3), 0.49 (s, 1H, NH), 0.15 (s, 9H, SiMe3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 42.0 (CH.sub.2), 35.0 (CH.sub.2), 32.1 (CH.sub.2), 29.7 (CH.sub.2), 29.5 (CH.sub.2), 27.1 (CH.sub.2), 22.8 (CH.sub.2), 14.1 (CH.sub.3), 0.0 (SiMe3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 3.0.

Stage 2: CO.SUB.2 .Insertion

[0145] 8.1 g (40.24 mmol) of N-trimethylsilyl-n-octylamine were mixed with 44 ml of dry THF and cooled in the ice bath. Gas entry of CO.sub.2 took place for 30 minutes while constantly stirring the reaction mixture. Subsequently, the solvent was removed by cold distillation and the insertion product was recovered as a clear, colorless liquid. 8.68 g (35.35 mmol) of N,n-octyl-O-trimethylsilyl-carbamate were obtained which corresponds to a yield of 88%. The identity and purity of the target compound were confirmed by NMR spectroscopy.

[0146] .sup.1H-NMR (400 MHz, CDCl.sub.3, δ [ppm]): 5.54 (s, 1H, NH), 3.10 (t, 2H, CH.sub.2), 1.49-1.29 (m, 12H, CH.sub.2), 0.88 (t, 3H, CH.sub.3), 0.26 (s, 9H, SiMe3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 155.5 (CO), 41.1 (CH.sub.2), 31.9 (CH.sub.2), 30.1 (CH.sub.2), 29.4 (CH.sub.2), 27.0 (CH.sub.2), 25.7 (CH.sub.2), 22.7 (CH.sub.2), 14.1 (CH.sub.3), 0.0 (SiMe3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 21.7.

Stage 3: Silylation

[0147] 8.68 g (35.35 mmol) of N,n-octyl-O-trimethylsilyl-carbamate were dissolved in 100 ml of n-pentane together with 3.64 g (35.99 mmol) of triethylamine and stirred in the ice bath. 8.05 g (36.23 mmol) of trimethylsilyltriflate were added dropwise via a dropping funnel. Formation of a second phase at the bottom of the Schlenk flask was observed. Subsequently, the mixture was stirred at room temperature for 3 hours. The 2.sup.nd phase formed was congealed in the dry ice/isopropanol cold mixture and the supernatant solution was decanted off. The solvent was removed by cold distillation thereby leaving a pale yellow, clear liquid in the reaction flask. In this way, 8.83 g (27.81 mmol) of N,O-bis(trimethylsilyl)-N,n-octyl-carbamate (2) were obtained. This corresponds to a yield of 79%. The identity and purity of the target compound were confirmed by NMR spectroscopy.

[0148] .sup.1H-NMR (400 MHz, CDCl.sub.3, δ [ppm]): 5.37 (s, 1H, NH), 3.01 (t, 2H, CH.sub.2), 1.38-1.20 (m, 12H, CH.sub.2), 0.80 (t, 3H, CH.sub.3), 0.20 (s, 9H, SiMe3), 0.14 (s, 9H, SiMe3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 157.6 (CO), 44.8 (CH.sub.2), 32.0 (CH.sub.2), 31.1 (CH.sub.2), 29.7 (CH.sub.2), 29.5 (CH.sub.2), 27.2 (CH.sub.2), 22.8 (CH.sub.2), 14.2 (CH.sub.3), 0.8 (SiMe3), 0.0 (SiMe3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 21.3, 8.8.

Stage 4: Thermolysis

[0149] A few milliliters of N,O-bis(trimethylsilyl)-N,n-octyl-carbamate (2) were filled into the still pot of the kugelrohr distillation apparatus under inert conditions. The still pot and the middle pot were put into the heating chamber (tubular furnace), while the outer pot was cooled in the water bath. The carbamate was heated to 300° C. for 2 hours, while the kugelrohr distillation apparatus was continuously rotated with 20 rpm. A colorless liquid accumulated in the outer pot. The middle pot at the end of the reaction time contained a yellow liquid, and the still pot was almost empty. Subsequently, the pots were cooled to room temperature and inert transferred to Schlenk vessels. The composition was analyzed by NMR spectroscopy. While in the middle pot there was still found undecomposed carbamate, in the .sup.29Si-NMR spectrum of the outer pot only the presence of hexamethyldisiloxane was shown. These results are confirmed by the .sup.13C-NMR spectra. In addition, in the .sup.13C-NMR spectra of the outer pot a signal at 120.5 ppm each was shown which can clearly assigned to the n-octyl isocyanate. While in the middle pot a variety of other signals is indicative of a mixture of substances of various species, only the isocyanate together with hexamethyldisiloxane is found in the sample of the outer pot (.sup.13C: δ=2.0 ppm). Comparing the analysis with a commercially available sample of the n-octyl isocyanate provided exact matches.

Example 3

Synthesis of 1,8-Diisocyanatooctane (16)

[0150] 1,8-Diisocyanatooctane (compound 16) was prepared according to the method shown in scheme 12. 1,8-Diisocyanatooctane is an example of an aliphatic diisocyanate.

Stage 1: Synthesis of Aminosilane

[0151] First, 3.10 g (21.52 mmol) of 1,8-diaminooctane together with 5.12 g (50.63 mmol) of triethylamine were provided in 140 ml diethyl ether. 4.99 g (45.97 mmol) of trimethyl chlorosilane were added under stirring in the ice bath via a dropping funnel. When adding the silane dropwise formation of a white solid and development of white smoke was observed. After having completely added the chlorosilane the mixture was stirred over night at room temperature. After having removed the white solid by filtration and the solvents under reduced pressure the aminosilane was obtained as a colorless liquid. In this way, 4.71 g (16.33 mmol) of N,N′-bis(trimethylsilyl)-1,8-diaminooctane were obtained. The yield is 76%. Purity of the product was confirmed by NMR spectroscopy.

[0152] .sup.1H-NMR (400 MHz, CDCl.sub.3, δ [ppm]): 2.81 (m, 4H, CH.sub.2), 1.49-1.41 (m, 12H, CH.sub.2), 0.45 (s, 2H, NH), 0.15 (s, 18H, SiMe3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 41.9 (CH.sub.2), 34.9 (CH.sub.2), 29.6 (CH.sub.2), 26.9 (CH.sub.2), 0.0 (SiMe3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 2.9.

Stage 2: CO.SUB.2 .Insertion

[0153] 7.04 g (24.39 mmol) of N,N′-bis(trimethylsilyl)-1,8-diaminooctane were mixed with 40 ml of dry THF. CO.sub.2 insertion was by gas entry for 20 minutes, while the reaction mixture was stirred and cooled in the ice bath. The solvent was removed under reduced pressure and the white solid obtained was dried in vacuum. In this way, 8.52 g (22.62 mmol) of 1,8-[O,O′-bis(trimethylsilyl)-carbamato]-octane were obtained in a yield of 93%. The identity and purity of the target compound were confirmed by NMR spectroscopy.

[0154] .sup.1H-NMR (400 MHz, CDCl.sub.3, δ [ppm]): 6.05 (s, 2H, NH), 3.06 (m, 4H, CH.sub.2), 1.46-1.31 (m, 12H, CH.sub.2), 0.08 (s, 18H, SiMe3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 155.6 (CO), 41.2 (CH.sub.2), 30.2 (CH.sub.2), 29.6 (CH.sub.2), 27.1 (CH.sub.2), 0.0 (SiMe3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 20.9.

Stage 3: Silylation

[0155] 6.22 g (16.53 mmol) of 1,8-[O,O′-bis(trimethylsilyl)-carbamato]-octane were dissolved in 50 ml of anisole with 3.37 g (33.34 mmol) of triethylamine. The mixture was stirred in the ice bath. 7.38 g (33.19 mmol) of trimethylsilyltriflate were added dropwise via a dropping funnel. Formation of a flake-like second phase was observed. Subsequently, the mixture was heated to room temperature and stirred at this temperature for 2 hours. The second phase formed was congealed in a cold mixture of dry ice and isopropanol and the supernatant solution was decanted off The solvent was removed under reduced pressure thereby precipitation of a white solid was observed. The solid was dried in vacuum for 4 hours. In this way, 8.12 g (15.58 mmol) of 1,8-[N,N′,O,O′-tetrakis(trimethylsilyl)-carbamato]-octane (6) were obtained which corresponds to a yield of 94%. The identity and purity of the target compound were confirmed by NMR spectroscopy.

[0156] .sup.1H-NMR (400 MHz, CDCl.sub.3, δ [ppm]): 8.78 (s, 2H, NH), 3.07 (m, 4H, CH.sub.2), 1.44-1.26 (m, 12H, CH.sub.2), 0.29 (s, 18H, SiMe3), 0.22 (s, 18H, SiMe3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 157.1 (CO), 44.8 (CH.sub.2), 30.9 (CH.sub.2), 29.5 (CH.sub.2), 27.0 (CH.sub.2), 0.8 (SiMe3), 0.0 (SiMe3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 22.0, 9.5.

Stage 4: Thermolysis

[0157] A few grams of 1,8-[N,N′,O,O′-tetrakis(trimethylsilyl)-carbamato]-octane (6) were filled into the still pot of the kugelrohr distillation apparatus under inert conditions. The still pot and the middle pot were put into the heating chamber (tubular furnace), while cooling the outer pot in the water bath. The carbamate was heated to 170° C. for 1 hour, to 200° C. for 1 hour, and to 250° C. for 30 min, while continuously rotating the kugelrohr distillation apparatus with 30 rpm. At the end of the heating phase accumulation of colorless liquid in the outer pot was observed, while in the still pot a yellow, polymer-like layer was formed. After thermolysis has taken place the individual pots of the kugelrohr distillation apparatus were separately analyzed by NMR spectroscopy. The presence of the diisocyanate was clearly detected by means of NMR and IR spectroscopy.

[0158] The .sup.13C-NMR spectrum of the outer pot in addition to hexamethyldisiloxane (.sup.13C: δ=2.0 ppm, .sup.29Si: δ=7.1 ppm) showed the diisocyanate at a shift of 120.5 ppm. The associated band in the IR-ATR spectrum is at 2253 cm.sup.−1. Comparing with a commercial sample of 1,8-diisocyanatooctane provided exact matches.

Example 4

Synthesis of Isopentyl-Isocyanate (21)

[0159] i-Pentyl-isocyanate (compound 21) was prepared according to the method shown in scheme 11. i-Pentyl-isocyanate is another example of an aliphatic mono-isocyanate. With respect to scheme 11, in example 4 R.sup.1 is i-pentyl, R.sup.2 and R.sup.3 at each occurrence are methyl, X.sup.1 is chlorine and X is triflate. The term “i-pentyl” or “isopentyl” is meant to be a group of formula (H.sub.3C).sub.2CH—CH.sub.2—CH.sub.2—.

[0160] N,O-Bis(trimethylsilyl)-N,i-pentyl-carbamate (22) is a compound of general formula IV-A in which R.sup.1 is i-pentyl. N,O-bis(trimethylsilyl)-N,i-pentyl-carbamate (22) has the following formula:

##STR00054##

Stage 1: Synthesis of Aminosilane

[0161] First, 5.65 g (64.81 mmol) of i-pentylamine together with 9.81 g (96.99 mmol) of triethylamine were provided in 150 ml of diethyl ether. 9.81 g (90.32 mmol) of trimethyl chlorosilane were added under stirring in the ice bath via a dropping funnel. When adding the silane dropwise formation of a white solid was observed in addition to the development of white smoke. Subsequently, the mixture was heated to room temperature and stirred for 96 hours. The solid was separated by filtration and the solvent was removed under reduced pressure. The aminosilane N-trimethylsilyl-i-pentylamine was obtained as a colorless liquid in a yield of 88% (9.12 g, 57.25 mmol). Purity of the product was confirmed by NMR spectroscopy.

[0162] .sup.1H-NMR (500 MHz, CDCl.sub.3, δ [ppm]): 2.69 (t, J=7.4 Hz, 2H), 1.60 (dq, J=13.4, 6.7 Hz, 1H), 1.29-1.21 (m, 2H), 0.85 (d, J=6.7 Hz, 6H), 0.24 (s, 1H, NH), 0.00 (s, 9H, SiMe.sub.3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 44.2 (CH.sub.2), 39.9 (CH.sub.2), 25.5 (CH), 22.6 (CH.sub.3), −0.1 (SiMe.sub.3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 3.0.

Stage 2: CO.SUB.2 .Insertion

[0163] 7.99 g (50.11 mmol) of N-trimethylsilyl-i-pentylamine were mixed with 10 ml of dry THF and transferred to an autoclave under inert conditions. The autoclave was pressurized with a CO.sub.2 pressure of 8 bar. The reaction was carried out under constant stirring for a period of 3 hours. After having relieved the pressure and inert transferred the reaction mixture to a Schlenk vessel the solvent was removed by cold distillation and the insertion product was recovered as a clear, colorless liquid. 9.55 g (46.98 mmol) of N,i-pentyl-O-trimethylsilyl-carbamate were obtained. This corresponds to a yield of 94%. The identity and purity of the target compound were confirmed by NMR spectroscopy.

[0164] .sup.1H-NMR (500 MHz, CDCl.sub.3, δ [ppm]): 5.19 (t, J=6.1 Hz, 1H, NH), 2.92-2.81 (m, 2H), 1.36 (dp, J=13.3, 6.7 Hz, 1H), 1.17-1.06 (m, 2H), 0.65 (d, J=6.7 Hz, 6H), 0.00 (s, 9H, SiMe.sub.3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 155.1 (CO), 40.1 (CH.sub.2), 39.0 (CH.sub.2), 25.5 (CH), 22.2 (CH.sub.3), −0.3 (SiMe.sub.3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 21.8.

Stage 3: Silylation

[0165] 9.55 g (46.98 mmol) of N,i-pentyl-O-trimethylsilyl-carbamate were dissolved in 90 ml of n-pentane together with 5.07 g (50.06 mmol) of triethylamine and stirred in the ice bath. 11.02 g (49.59 mmol) of trimethylsilyltriflate were added dropwise via a dropping funnel thereby formation of a white second phase at the bottom of the Schlenk flask was observed. Subsequently, the mixture was stirred over night at room temperature. The 2.sup.nd phase formed was congealed in the dry ice/isopropanol cold mixture—and the supernatant solution was decanted off The solvent was removed by cold distillation. In this way, 8.38 g (30.40 mmol, yield 65%) of N,O-bis(trimethylsilyl)-N,i-pentyl-carbamate (22) were obtained as a pale yellow liquid. The identity of the target product was confirmed by NMR spectroscopy.

[0166] .sup.1H-NMR (500 MHz, CDCl.sub.3, δ [ppm]): 2.93-2.80 (m, 2H), 1.31 (dh, J=13.3, 6.7 Hz, 1H), 1.13 (ddd, J=11.7, 7.6, 5.9 Hz, 2H), 0.67 (d, J=6.7 Hz, 6H), 0.06 (s, 9H, SiMe.sub.3), 0.00 (s, 9H, SiMe.sub.3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 157.3 (CO), 43.0 (CH.sub.2), 39.6 (CH.sub.2), 26.2 (CH), 22.4 (CH.sub.3), 0.5 (SiMe.sub.3), −0.3 (SiMe.sub.3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 21.9 (Si-O), 9.5 (Si-N).

Stage 4: Thermolysis

[0167] 1.38 g (4.99 mmol) of N,O-bis(trimethylsilyl)-N,i-pentyl-carbamate (22) were filled into the still pot of the kugelrohr distillation apparatus under inert conditions. The still pot and the middle pot were put into the heating chamber (tubular furnace) and the apparatus was adjusted to an inclination of 45°. The carbamate was heated to 250° C. for 1 hour and to 300° C. for another 30 min at continuous rotation at 30 rpm. Subsequently, the apparatus was brought into a horizontal position and heated to 300° C. for 30 min again. In the outer and middle pots a colorless liquid has accumulated. At the end of the reaction time the still pot was almost empty. Subsequently, the pots were cooled to room temperature and inert transferred to Schlenk vessels. Analysis of the colorless liquid of the outer pot was carried out by means of NMR spectroscopy. The .sup.29Si-NMR spectrum only indicates the presence of hexamethyldisiloxane (7.1 ppm). The carbamate used is completely decomposed. These results are confirmed by the .sup.13C-NMR spectrum (hexamethyldisiloxane at 1.7 ppm). Moreover, a signal at 122.2 ppm is found in the .sup.13C-NMR spectrum which can clearly be assigned to the isopentyl-isocyanate (other associated signals: 41.0, 40.1, 25.2, 21.9 ppm). Assignment was additionally confirmed by IR spectroscopy. The characteristic vibration of the carbonyl group of the carbamate at about 1690 cm.sup.−1 has completely disappeared, while the intensive isocyanate band is found at 2270 cm.sup.−1. The bands at 1252, 1053, 841 cm.sup.−1 can be assigned to the hexamethyldisiloxane.

Example 5

Synthesis of Benzylisocyanate (23)

[0168] Benzylisocyanate (compound 23) was prepared according to the method shown in scheme 11. Benzylisocyanate is another example of an aliphatic monoisocyanate. With respect to scheme 11, in example 5 R.sup.1 is benzyl, R.sup.2 and R.sup.3 at each occurrence are methyl, X.sup.1 is chlorine and X is triflate. The term “benzyl” is meant to be a group of formula H.sub.5C.sub.6—CH.sub.2—.

Stage 1: Synthesis of Aminosilane

[0169] First, 5.03 g (46.90 mmol) of benzylamine together with 4.91 g (48.55 mmol) of triethylamine were provided in 160 ml of diethyl ether. 5.17 g (47.56 mmol) of trimethyl chlorosilane were added via a dropping funnel under stirring in the ice bath whereby formation of a white solid and development of white smoke was observed. Subsequently, the mixture was heated to room temperature and stirred overnight. The solid was separated by filtration and the solvent was removed by cold distillation. The aminosilane N-trimethylsilyl-benzylamine was obtained as a colorless liquid in a yield of 89% (7.45 g, 41.52 mmol). Purity of the product was confirmed by NMR spectroscopy.

[0170] .sup.1H-NMR (500 MHz, CDCl.sub.3, δ [ppm]): 7.15 (m, 4H), 7.05 (m, 1H), 3.77 (d, J=8.0 Hz, 2H), 0.55 (s, 1H, NH), 0.00 (s, 9H, SiMe.sub.3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 144.2 (C), 128.1 (CH), 126.8 (CH), 126.3 (CH), 45.6 (CH.sub.2), 0.0 (SiMe.sub.3).

[0171] .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 3.9.

Stage 2: CO.SUB.2 .Insertion

[0172] 6.78 g (37.81 mmol) of N-trimethylsilyl-benzylamine were mixed with 20 ml of dry THF, transferred to an autoclave under inert conditions and pressurized with a CO.sub.2 pressure of 8 bar within one hour. After having relieved the pressure and inert transferred the reaction mixture to a Schlenk vessel the solvent was removed by cold distillation and the insertion product was recovered as a colorless, viscous liquid with a yield of 94% (7.90 g, 35.37 mmol). After some days of storage at room temperature formation of colorless crystals was observed. The identity and purity of the target compound was confirmed by NMR spectroscopy.

[0173] .sup.1H-NMR (500 MHz, CDCl.sub.3, δ [ppm]): 7.14 (m, 5H), 6.17 (s, 1H, NH), 4.15 (d, J=6.2 Hz, 2H, CH.sub.2), 0.23 (s, 9H, SiMe.sub.3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 155.0 (CO), 128.6 (C), 127.8 (CH), 126.8 (CH), 126.5 (CH), 44.2 (CH2), −0.5 (SiMe.sub.3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 23.2. Elemental analysis: calculated N 6.27%, C 59.16%, H 7.67%, measured N 6.81%, C 59.02%, H 7.408%

Stage 3: Silylation

[0174] 30.33 g (135.80 mmol) of N-benzyl-O-trimethylsilyl-carbamate were dissolved in 100 ml of diethyl ether together with 14.48 g (143.07 mmol) of triethylamine and stirred in the ice bath. 32.62 g (146.76 mmol) of trimethylsilyltriflate were added dropwise via a dropping funnel thereby formation of a white second phase was observed at the bottom of the Schlenk flask. Subsequently, the mixture was stirred at room temperature overnight, before the 2.sup.nd phase formed was congealed in the dry ice/isopropanol cold mixture and the supernatant solution was decanted off. The solvent was removed from the reaction solution by cold distillation and provided the target product, N,O-bis(trimethylsilyl)-N-benzyl-carbamate (5), as an intensively yellow, slightly viscous liquid (37.58 g, 127.17 mmol, 94% yield). The identity of the target product was confirmed by NMR spectroscopy.

[0175] .sup.1H-NMR (500 MHz, CDCl.sub.3, δ [ppm]): 7.18 (m, 5H), 4.41 (s, 2H, CH.sub.2), 0.33 (s, 9H, SiMe.sub.3), 0.19 (s, 9H, SiMe.sub.3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 158.2 (CO), 140.4 (C), 128.4 (CH), 126.6 (CH), 126.4 (CH), 48.1 (CH.sub.2), 0.8 (SiMe.sub.3), 0.0 (SiMe.sub.3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 22.6 (O-Si), 10.9 (N-Si).

Stage 4: Thermolysis

[0176] 3.13 g (4.50 mmol) of N,O-bis(trimethylsilyl)-N-benzyl-carbamate (5) were filled into the still pot of the kugelrohr distillation apparatus under inert conditions. The still pot and the middle pot were put into the heating chamber (tubular furnace) and the apparatus was adjusted to an inclination of 45°. The carbamate was heated to 200° C. and 250° C. for 30 minutes each, to 300° C. for 10 minutes, and to 250° C. for another 90 minutes with continuous rotation at 20 rpm. Pressure compensation was ensured via an oil trap. 50 Minutes after the start of heating the apparatus was placed in a horizontal position. A colorless liquid (1.82 g) has accumulated in the outer pot and a yellow liquid (0.38 g) in the middle pot from 250° C. At the end of the reaction time a small amount of a highly viscous, dark brown residue (0.64 g) was contained in the still pot. Subsequently, the pots were cooled to room temperature and inert transferred to Schlenk vessels with CDCl.sub.3 as the solvent. Analysis of the fractions was by NMR spectroscopy.

[0177] Outer pot: The .sup.29Si-NMR spectrum only indicated the presence of hexamethyldisiloxane (7.3 ppm). The carbamate used was completely decomposed. These results were confirmed by the .sup.13C-NMR spectrum (hexamethyldisiloxane at 1.7 ppm). Moreover, signals were found in the .sup.13C-NMR spectrum which can clearly be assigned to the benzylisocyanate by comparison with a commercially available sample (137.0, 128.7, 127.8, 126.6, 123.7, 46.4 ppm). Both the middle fraction and the residue showed a variety of signals in the .sup.29Si and .sup.13C-NMR spectra. An assignment could not be made. Analysis by gas chromatography provided further information on the composition of the outer fraction: retention time (RT) 1.565 min —16.95%—CDCl.sub.3; RT 1.771 min—0.68%—Me.sub.3Si-isocyanate (wherein Me designates a methyl group); RT 2.043 min—64.85%—hexamethyldisiloxane (HMDSO); RT 2.554 min—3.67%—toluene; RT 6.447 min—9.48%—benzylisocyanate (23); RT 10.765 min—0.81%—N,O-bis(trimethylsilyl)-N-benzyl-carbamate (5).

[0178] In another experiment, 8.38 g (28.36 mmol) of N,O-bis(trimethylsilyl)-N-benzyl-carbamate (5) were directly heated to 300° C. for 2.5 hours in the kugelrohr distillation apparatus at 30 rpm under standard pressure. For the first hour the apparatus was adjusted to an inclination of 45°. After expiration of the reaction time a colorless liquid with white flakes has accumulated in the outer pot (1.74 g), while the middle pot was almost empty (0.22 g) and a highly viscous, deep brown residue (2.47 g) has formed in the still pot. All fractions were analyzed by NMR spectroscopy. Again, a variety of signals has appeared in the .sup.29Si and .sup.13C-NMR spectra of the middle pot and the residue which could not further be assigned. The outer pot in addition to HMDSO (7.3 ppm) also contained trimethylsilylisocyanate (4.2 ppm) as the silicon-containing component in the .sup.29Si-NMR spectrum. This was confirmed in the .sup.13C-NMR spectrum: HMDSO (1.9 ppm), Me.sub.3SiNCO (0.9, 124.0 ppm). In addition, it was noted that the CH.sub.2 bridge of the benzyl group at about 46 ppm was not present, but instead an intensive signal appeared at 21.5 ppm. Formation of toluene was identified together with the signals in the aromatic shift area (137.9, 129.2, 128.4, 125.5, 21.5 ppm).

Example 6

Synthesis of Allylisocyanate (24)

[0179] Allylisocyanate (compound 24) was prepared according to the method shown in scheme 11. Allylisocyanate is another example of an aliphatic monoisocyanate. With respect to scheme 11, in example 6 R.sup.1 is allyl, R.sup.2 and R.sup.3 at each occurrence are methyl, X.sup.1 is chlorine and X is triflate. The term “allyl” is meant to be a group of formula H.sub.2C═CH—CH.sub.2—.

[0180] N,O-Bis(trimethylsilyl)-N-allyl-carbamate (25) is a compound of general formula IV-A in which R.sup.1 is allyl. N,O-Bis(trimethylsilyl)-N-allyl-carbamate (25) has the following formula:

##STR00055##

Stage 1: Synthesis of Aminosilane

[0181] To a mixture of 5.07 g (88.75 mmol) of allylamine and 8.86 g (87.53 mmol) of triethylamine in 100 ml dry n-pentane 9.73 g (89.59 mmol) of trimethylchlorosilane were added dropwise under stirring and cooling with an ice bath. A white precipitate was formed which was separated by filtration after 2 days of stirring at room temperature. The solvent was separated by cold distillation and the success of the synthesis was examined by NMR spectroscopy. In addition to the desired N-trimethylsilyl-allylamine (26) the associated silazane (N,N-bis(trimethylsilyl)-allylamine (27) was formed.

[0182] .sup.1H-NMR (500 MHz, CDCl.sub.3, δ [ppm]): 5.82-5.59 (m, 1H), 4.2 (dd, J=17.0, 1.8 Hz, 2H), 4.76 (dd, J=10.1, 1.5 Hz, 1H), 3.26 (dt, J=4.4, 2.0 Hz, OH), 3.14 (d, J=5.3 Hz, 7H), −0.09 (s, 2H), −0.15 (s, 9H, SiMe.sub.3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 141.2 (27)/140.9 (26) (CH), 113.3 (27)/112.8 (26) (CH2), 47.4 (27)/44.6 (26) (CH.sub.2), 0.0 (SiMe.sub.3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 4.1 (26), 6.5 (27).

Stage 2: CO.SUB.2 .Insertion

[0183] 7.65 g (59.18 mmol) of N-trimethylsilyl-allylamine (commercially purchased) were mixed with 20 ml of dry THF and transferred to an autoclave under inert conditions. CO.sub.2 insertion reaction was performed with a CO.sub.2 pressure of 8 bar with constant stirring for a period of 43.5 hours. After having relieved the pressure and inert transferred the reaction mixture with 5 ml of THF to a Schlenk vessel the solvent was removed by cold distillation and the insertion product was recovered as an intensively yellow, slightly viscous liquid. In this way, 9.55 g (55.10 mmol, yield 93%) of N-allyl-O-trimethylsilyl-carbamate were obtained. The identity and purity of the target compound were confirmed by NMR spectroscopy.

[0184] .sup.1H-NMR (500 MHz, CDCl.sub.3, δ [ppm]): 5.70-5.45 (m, 1H), 5.29 (s, 1H, NH), 4.93 (dd, J=17.2, 1.6 Hz, 1H), 4.84 (dd, J=10.3, 1.5 Hz, 1H), 3.50 (t, J=5.7 Hz, 2H), 0.04 (s, 9H, SiMe.sub.3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 155.6 (CO), 135.2 (CH), 115.7 (CH.sub.2), 43.7 (CH.sub.2), 0.3 (SiMe.sub.3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 22.3.

Stage 3: Silylation

[0185] 8.43 g (48.62 mmol) of N-allyl-O-trimethylsilyl-carbamate were dissolved in 100 ml of n-pentane together with 5.28 g (52.14 mmol) of triethylamine and stirred in an ice bath. 11.37 g (51.15 mmol) of trimethylsilyltriflate were added dropwise thereby formation of an intensively orange, second phase was observed at the bottom of the Schlenk flask. Subsequently, the mixture was stirred overnight at room temperature. The 2.sup.nd phase obtained was congealed in the dry ice/isopropanol cold mixture and the supernatant solution was decanted off. After having removed the solvent by cold distillation 10.24 g (41.70 mmol, yield 86%) of N,O-bis(trimethylsilyl)-N-allyl-carbamate (25) were obtained as an orange liquid. The identity of the target product was confirmed by NMR spectroscopy.

[0186] .sup.1H-NMR (500 MHz, CDCl.sub.3, δ [ppm]): 5.67-5.53 (m, 1H), 4.88 (d, J=1.8 Hz, 2H), 4.86-4.80 (m, 2H), 3.56 (d, J=5.1 Hz, 2H), 0.10 (s, 9H, SiMe.sub.3), 0.04 (s, 9H, SiMe.sub.3). .sup.13C-NMR (101 MHz, CDCl.sub.3, δ [ppm]): 157.4 (CO), 136.1 (CH), 114.3 (CH.sub.2), 46.7 (CH.sub.2), 0.6 (SiMe.sub.3), −0.1 (SiMe.sub.3). .sup.29Si-NMR (79 MHz, CDCl.sub.3, δ [ppm]): 22.4 (Si-O), 10.5 (Si-N).

Stage 4: Thermolysis

[0187] 1.09 g (4.43 mmol) of N,O-bis(trimethylsilyl)-N-allyl-carbamate (25) were filled into the still pot of the kugelrohr distillation apparatus under inert conditions and put into the heating chamber (tubular furnace) together with the middle pot. The apparatus was adjusted to an inclination of 45°. The carbamate was heated to 250° C. for 1 hour and to 300° C. for another 30 min with continuous rotation at 30 rpm under standard pressure. The apparatus was placed in the horizontal position one hour after starting heating. In the outer pot a colorless liquid has accumulated. While the middle pot at the end of the reaction time was almost empty, a black film has formed on the glass wall in the still pot. Subsequently, the pots were cooled to room temperature and the outer fraction was inert transferred to Schlenk vessels, before the composition was analyzed NMR spectroscopy. The .sup.29Si-NMR spectrum only indicated the presence of hexamethyldisiloxane (7.2 ppm), while the carbamate used was completely decomposed. These results were confirmed by the .sup.13C-NMR spectrum (hexamethyldisiloxane at 2.0 ppm). The other signals in the .sup.13C-NMR spectrum indicated an exact match with a sample of commercially available allylisocyanate. The signals are located as follows: 133.3, 123.9, 116.1, 39.7 ppm. The assignment was additionally confirmed by the characteristic vibration of the isocyanate group at 2262 cm.sup.−1 in the IR spectrum. Determination of contents by gas chromatography resulted in a composition of 66.05% of hexamethyldisiloxane and 28.38% of allylisocyanate.