METHOD FOR PRODUCING C4-C15 LACTAMS

Abstract

The present invention relates to a process for preparing C.sub.4-C.sub.15 lactams, in which a C.sub.1-C.sub.10-alkyl nitrite is reacted with a C.sub.4-C.sub.15-cycloalkane and is illuminated with a light-emitting diode during the reaction. This forms a C.sub.4-C.sub.15-cyclohexanone oxime which is then converted further to a C.sub.4-C.sub.15 lactam; the C.sub.1-C.sub.10 alcohol formed is recycled into the preparation of the C.sub.1-C.sub.10-alkyl nitrite.

Claims

1.-12. (canceled)

13. A process for preparing C.sub.4-C.sub.15 lactams, comprising the steps of: a) converting a first mixture (M1) comprising a C.sub.1-C.sub.10 alcohol, nitrogen oxides and oxygen to obtain a C.sub.1-C.sub.10-alkyl nitrite, b) converting a second mixture (M2) comprising the C.sub.1-C.sub.10-alkyl nitrite obtained in step a) and a C.sub.4-C.sub.15-cycloalkane to obtain a first product mixture (P1) comprising a C.sub.4-C.sub.15-nitrosocycloalkane, a dimeric C.sub.4-C.sub.15-nitrosocycloalkane, a C.sub.4-C.sub.15-cycloalkanone oxime and a C.sub.1-C.sub.10 alcohol, wherein the second mixture (M2) is illuminated during the conversion with a light-emitting diode that emits light having a wavelength in the range from 300 to 500 nm, c) preparing the C.sub.4-C.sub.15 lactam by conversion of the C.sub.4-C.sub.15-cycloalkanone oxime obtained in step b) in the presence of a catalyst by one of the following steps: c1) separating the C.sub.1-C.sub.10 alcohol from the first product mixture (P1) obtained in step b) to obtain a second product mixture (P2) comprising the C.sub.4-C.sub.15-cycloalkanone oxime, recycling the C.sub.1-C.sub.10 alcohol removed into the first mixture (M1) in step a) and converting the C.sub.4-C.sub.15-cycloalkanone oxime present in the second product mixture (P2) in the presence of the catalyst to obtain the C.sub.4-C.sub.15 lactam, or c2) converting the C.sub.1-C.sub.15-cycloalkanone oxime present in the first product mixture (P1) in the presence of the catalyst to obtain a third product mixture (P3) comprising the C.sub.4-C.sub.15 lactam and the C.sub.1-C.sub.10 alcohol, removing the C.sub.1-C.sub.10 alcohol present in the third product mixture (P3) to obtain the C.sub.1-C.sub.15 lactam and recycling the C.sub.1-C.sub.10 alcohol removed into the first mixture (M1) in step a).

14. The process according to claim 13, wherein the light-emitting diode in step b) emits light having a wavelength in the range from 340 to 390 nm.

15. The process according to claim 13, wherein the conversion of the first mixture (M1) in step a) is conducted at a temperature in the range from 10 to 300 C.

16. The process according to claim 13, wherein the conversion of the first mixture (M1) in step a) is conducted at a pressure in the range from 1 to 50 bar.

17. The process according to claim 13, wherein the conversion of the second mixture (M2) in step b) is conducted at a temperature in the range from 30 to 150 C.

18. The process according to claim 13, wherein the conversion of the second mixture (M2) in step b) is conducted at a pressure in the range from 1 to 10 bar.

19. The process according to claim 13, wherein the catalyst in step c) is selected from the group consisting of zeolites and inorganic acids.

20. The process according to claim 13, wherein the C.sub.4-C.sub.15-cycloalkanone oxime is in gaseous form during the conversion of the C.sub.4-C.sub.15-cycloalkanone oxime in step c).

21. The process according to claim 13, wherein the conversion of the C.sub.4-C.sub.15-cycloalkanone oxime in step c) is conducted at a temperature in the range from 50 to 500 C.

22. The process according to claim 13, wherein the conversion of the C.sub.4-C.sub.15-cycloalkanone oxime in step c) is conducted at a pressure in the range from 0.05 to 10 bar.

23. The process according to claim 13, wherein the C.sub.4-C.sub.15-cycloalkane in step b) is selected from the group consisting of cyclopentane, cyclohexane and cyclododecane.

24. The process according to claim 13, wherein the C.sub.1-C.sub.10 alcohol present in the first mixture (M1) in step a) is selected from the group consisting of methanol, tert-butanol and neopentanol.

Description

EXAMPLES

Examples I1 to I6

[0153] tert-Butyl nitrite (90% by weight in tert-butanol, Sigma-Aldrich) and cyclohexane (Sigma-Aldrich), in the ratio specified in table 1, were illuminated in a borosilicate tube sealed with a Teflon screwtop at room temperature (20 C.) while stirring for 16 hours. Illumination was effected using a light-emitting diode (Nichia SMD LED UV NVSU233a) which emits light having a wavelength of 365 nm and has light intensity 1 W at 3.7 V and 1 A, applied to an aluminum heatsink. This formed the first product mixture. For determination of nitrosocyclohexane and cyclohexanone oxime in the first product mixture formed, 0.08 ml of the first product mixture was dissolved in 0.8 ml of benzene-d.sub.6, and 0.01 ml of mesitylene was added as internal standard. Subsequently, the content of nitrosocyclohexane and the cyclohexanone oxime was determined by means of .sup.1H NMR spectroscopy.

TABLE-US-00001 TABLE 1 tert-Butyl Cyclohexanone Exam- nitrite Cyclohexane Nitrosocyclohexane oxime ple [mol] [mol] [%] [%].sup.1 I1 0.2 10 n.d. 49.8 I2 0.25 10 n.d. 40.0 I3 0.33 10 n.d. 45.5 I4 0.5 10 n.d. 40.2 I5 0.67 10 15.8 32.3 I6 1.2 8.4 19.2 32.3 .sup.1The percentages are based on the crude yield of nitrosocyclohexane or of cyclohexanone oxime based on tert-butyl nitrite

Example 17

[0154] tert-Butyl nitrite (90% by weight in tert-butanol; 2.5 mmol, 0.33 ml; Sigma-Aldrich) and cyclohexane (50 mmol, 5.41 ml; Sigma-Aldrich) was illuminated in a closed borosilicate glass tube while stirring for 16 hours to obtain the first product mixture. The light source used was a light-emitting diode which emits light having a wavelength of 365 nm (Nichia SMD LED UV NVSU233a having a light intensity of 1 W at 3.7 V and 1 A).

[0155] For determination of nitrosocyclohexane and cyclohexanone oxime in the first product mixture formed, 0.08 ml of the first product mixture was dissolved in 0.8 ml of benzene-d.sub.6, and 0.01 ml of mesitylene was added as internal standard. Subsequently, the content of nitrosocyclohexane and the cyclohexanone oxime was determined by means of .sup.1H NMR spectroscopy. Crude yields of 19% nitrosocyclohexane and 38% cyclohexanone oxime based on tert-butyl nitrite were obtained in the first product mixture.

[0156] After the reaction, all volatile constituents were removed from the first product mixture (P1) obtained and a mixture of nitrosocyclohexane and cyclohexanone oxime was obtained as a solid residue. This mixture was purified by means of column chromatography on silica gel with a 4:1 mixture of petroleum ether and ethyl acetate and then the composition of the product was determined by .sup.1H NMR spectroscopy, mass spectroscopy and elemental analysis. In relation to the nitrite used, 48% cyclohexanone oxime and 8% nitrosocyclohexane were obtained.

Examples I8 to I27

[0157] A second mixture consisting of tert-butyl nitrite (90% by weight in tert-butanol, Sigma-Aldrich; 0.5 mmol) and cyclohexane (Sigma-Aldrich; 10 mmol) was illuminated in a borosilicate tube sealed with a Teflon screwtop at 25 C. (table 2) and at 50 C. (table 3) while stirring for the periods of time specified in tables 2 and 3 (reaction time). Illumination was effected using a light-emitting diode (Nichia SMD LED UV NVSU233a) which emits light having a wavelength of 365 nm and has light intensity 1 W at 3.7 V and 1 A, applied to an aluminum heatsink. This formed the first product mixture. The determination of nitrosocyclohexane and cyclohexanone oxime in the first product mixture formed was effected as described in examples B1 to B6 by means of .sup.1H NMR spectroscopy.

[0158] The crude yields achieved as a function of reaction time are shown in tables 2 and 3.

TABLE-US-00002 TABLE 2 Cyclohexanone Reaction time Nitrosocyclohexane oxime Example [h] [%] [%].sup.1 I8 0.25 23 I9 0.5 29 I10 1 37 5 I11 1.5 45 9 I12 2 45 9 I13 3 33 7 I14 4 29 14 I15 5 27 25 I16 6 14 36 .sup.1The percentages are based on the crude yield of nitrosocyclohexane or of cyclohexanone oxime based on tert-butyl nitrite

TABLE-US-00003 TABLE 3 Cyclohexanone Reaction time Nitrosocyclohexane oxime Example [min] [%] [%].sup.1 I17 5 I18 10 I19 15 6 I20 20 16 I21 30 23 I22 45 25 I23 90 52 8 I24 120 49 12 I25 180 47 9 I26 240 43 20 I27 300 35 27 .sup.1The percentages are based on the crude yield of nitrosocyclohexane or of cyclohexanone oxime based on tert-butyl nitrite

Example I28

[0159] A second mixture consisting of tert-butyl nitrite (90% by weight in tert-butanol, Sigma-Aldrich; 0.5 mmol, 66 l), cyclododecane (10 mmol; 1683 mg) and 1 ml of benzene was illuminated in a closed borosilicate tube at room temperature (29 C.) while stirring for 16 hours. Illumination was effected using a light-emitting diode (Nichia SMD LED UV NVSU233a) which emits light having a wavelength of 365 nm and has light intensity 1 W at 3.7 V and 1 A, applied to an aluminum heatsink. This formed the first product mixture. Nitrosocyclododecane and dodecanone oxime were determined in the first product mixture formed as described for nitrosocyclohexane and cyclohexanone oxime in examples 11 to 16 by means of .sup.1H NMR spectroscopy. 46% crude yield of nitrocyclododecane based on tert-butyl nitrite was achieved.

Example I29

[0160] A second mixture consisting of tert-butyl nitrite (90% by weight in tert-butanol, Sigma-Aldrich; 0.5 mmol, 66 l) and cyclopentane (10 mmol; 933 l) was illuminated in a closed borosilicate tube at room temperature (20 C.) while stirring for 16 hours to obtain the first product mixture. Illumination was effected using a light-emitting diode (Nichia SMD LED UV NVSU233a) which emits light having a wavelength of 365 nm and has light intensity 1 W at 3.7 V and 1 A, applied to an aluminum heatsink. The determination of nitrosocyclopentane and cyclopentanone oxime in the first product mixture formed was effected by means of .sup.1H NMR spectroscopy as described in examples B1 to B6 for nitrosocyclohexane and cyclohexanone oxime. A crude yield of cyclopentanone oxime of 61% based on tert-butyl nitrite was achieved.

Comparative Examples C.SUB.30 .to C.SUB.37

[0161] A second mixture consisting of tert-butyl nitrite (90% by weight in tert-butanol; Sigma-Aldrich) and cyclohexane (Sigma-Aldrich) in the molar ratios specified in table 4 was illuminated in a quartz tube (for examples C.sub.30 to C.sub.33 a tube having a diameter of 10 mm was used, and for examples C.sub.34 to C.sub.37 a tube having a diameter of 6 mm) with a mercury vapor lamp (Normac UV-lamps TQ150 Z2; 200 nm) at room temperature (20 C.) while stirring. This formed the first product mixture. The determination of nitrosocyclohexane and cyclohexanone oxime in the first product mixture formed was effected after one hour and after four hours of illumination by means of .sup.1H NMR spectroscopy as described in examples I1 to I6.

[0162] The results are shown in table 4.

TABLE-US-00004 TABLE 4 tert- Butyl Nitrosocyclohexane Cyclohexanone Ex- nitrite Cyclohexane [%] oxime [%].sup.1 ample [mmol] [mmol] after 1 h after 4 h after 1 h after 4 h C30 0.10 10 30 0 0 8 C31 0.13 10 30 18 0 12 C32 0.20 10 35 20 0 14 C33 0.50 10 10 29 0 2 C34 0.10 10 0 0 0 19 C35 0.13 10 0 0 0 33 C36 0.20 10 5 0 0 20 C37 0.50 10 23 7 2 20 .sup.1The percentages are based on the crude yield of nitrosocyclohexane or of cyclohexanone oxime based on tert-butyl nitrite

Comparative Example C38

[0163] A second mixture consisting of 188.4 g (2.239 mol) of cyclohexane and 11.6 g (112.5 mmol) of tert-butyl nitrite was pumped through a Teflon hose having a length of 3.8 m and an internal diameter 2 mm, which was wound around a cooling quartz tube of a mercury vapor lamp (150 W; TQ150, undoped). During that time, the second mixture was illuminated with the mercury vapor lamp. The composition of the first product mixture obtained was determined by means of quantitative HPLC by the method below. Table 5 reports the composition of the first product mixture obtained as a function of the residence time of the second mixture in the Teflon hose.

[0164] For the quantitative HPLC determination, an Agilent Series 1100 was used. The column used was a Zorbax Eclipse XDB-C18 1.8 m 50*4.6 mm from Agilent. A UV detector (A=195 nm, BW=5 nm) was used; the flow rate was 1.3 ml/min, the injection was 5 l, at a temperature of 20 C., a run time of 10 min and a pressure of about 250 bar. The eluent used was water with 0.1% by volume of H.sub.3PO.sub.4 or acetonitrile with 0.1% by volume of H.sub.3PO.sub.4. Calibration was effected with an external standard, with dissolution of the samples in an acetonitrile/water mixture (50% by volume/50% by volume). The first product mixture was likewise dissolved in this acetonitrile/water mixture. The spectrum obtained was evaluated by methods known to those skilled in the art.

TABLE-US-00005 TABLE 5 t-Butyl Cyclohexanone Isomer of Residence nitrite oxime Dimer.sup.1 the dimer.sup.2 Yield Run time [min] [mmol] [mmol] [mmol]* [mmol]* [%] 1 0.00 92.2 0.0 0.6 0.0 1 2 2.64 52.1 0.6 6.4 3.5 11 3 3.97 44.4 2.3 6.7 4.9 15 4 5.95 27.2 3.7 8.6 6.0 20 5 11.90 5.3 5.7 7.8 8.7 24 *calculated as monomer [00002][00003]

Comparative Example C39

[0165] A second mixture consisting of 376.8 g (4.477 mol) of cyclohexane and 23.2 g (225 mmol) of tert-butyl nitrite was pumped through a Teflon hose (length 3.8 m; internal diameter 2 mm; residence time 5.95 min.) which was wound around a cooling borosilicate tube of a mercury vapor lamp (150 W; TQ150, undoped). During that time, the second mixture was illuminated with the mercury vapor lamp. After illumination, cyclohexane and residual tert-butyl nitrite were evaporated and 24 g of n-hexane were added. The suspension was cooled to 0 C., filtered and washed with 10 ml of n-hexane at 0 C. 1.95 g (8.6 mmol) of the dimer were obtained.

Example I40

[0166] A sample of a second mixture consisting of 188.4 g (2.24 mol) of cyclohexane and 11.6 g (11.2 mmol) of tert-butyl nitrite were introduced into a cuvette (381385 mm) and illuminated with 10 diodes which emit light having a wavelength of 365 nm. Table 6 reports the composition of the first product mixture obtained as a function of the reaction time (illumination time), with determination of the composition of the first product mixture by means of quantitative HPLC as described above in example 138.

TABLE-US-00006 TABLE 6 t-Butyl Cyclohexanone Isomer of Reaction nitrite oxime Dimer.sup.1 the dimer.sup.2 Yield time [min] [mmol] [mmol] [mmol]* [mmol]* [%] 0 8.07 0.00 0.00 0.00 0 15 5.42 1.61 0.44 0.00 22.7 30 2.86 3.24 0.73 0.02 44.7 45 0.80 4.41 0.87 0.03 60.6 60 0.00 4.63 1.14 0.05 67.3 *calculated as monomer [00004][00005]

Example I41

[0167] A second mixture consisting of 568 g (6.75 mol) of cyclohexane and 34.8 g (337.5 mmol) of tert-butyl nitrite was pumped through a cuvette (381385 mm), with a residence time of the second mixture in the cuvette of 5.95 min, during which the second mixture was illuminated with 10 diodes which emit light having a wavelength of 365 nm. After the illumination, cyclohexane and tert-butyl nitrite were evaporated at a maximum of 40 C. and there were two cycles of addition of 20 g of n-hexane and re-evaporation. The residue was suspended in 30 g of hexane. The suspension cooled to 0 C., filtered and washed with 10 ml of n-hexane. 10.2 g (45 mmol, 13%) of dimer were obtained.

Examples I42 and I43

[0168] A second mixture consisting of the components specified in table 7 in the molar ratios specified in table 7 was introduced into a cuvette (381385 mm) and illuminated with 10 diodes which emit light having a wavelength of 365 nm for the period of time specified in table 7. The composition of the first product mixture which forms was determined by means of quantitative HPLC as described above in example 138. Table 7 shows the results.

TABLE-US-00007 TABLE 7 I42 I43 Molar cyclohexane:tert-butyl 20:1:8 20:1:0 nitrite:tert-butanol ratio tert-Butyl nitrite [mmol] 6.89 9.21 Illumination time [min] 45 60 First product mixture (P1) tert-Butyl nitrite [mmol] 0.1 0 Dimer.sup.1 [mmol]* 2.93 4.63 Isomer of the dimer.sup.2 [mmol]* 0.77 1.14 Cyclohexanone oxime [%] 0.93 0.43 Yield.sup.3 [%] 67.2 67.3 Yield.sup.4 [%] 68.2 67.3 *calculated as monomer [00006][00007].sup.3based on tert-butyl nitrite used .sup.4based on tert-butyl nitrite converted

Examples I44 and I45

[0169] A second mixture consisting of cyclohexane and tert-butyl nitrite in a molar ratio of 20:1 was introduced into a cuvette (381385 mm) and illuminated with the number of diodes specified in table 8 and with the illumination time specified in table 8. The composition of the first product mixture formed was determined by means of quantitative HPLC as described in example 138. The results can be seen in table 8.

TABLE-US-00008 TABLE 8 I44 I45 Number of diodes 5 10 Illumination time [min] 90 45 Stirring yes no First product mixture (P1) tert-Butyl nitrite [mmol] 1.74 1.22 Dimer.sup.1 [mmol] 6.62 6.72 Isomer of the dimer.sup.2 [mmol]* 1.19 1.33 Cyclohexanone oxime [%] 0.44 0.47 Yield.sup.3 [%] 58.9 60.8 Yield.sup.4 [%] 67.3 66.6 *calculated as monomer [00008][00009].sup.3based on tert-butyl nitrite used .sup.4based on tert-butyl nitrite converted