PROCESS FOR THE TRANSFORMATION OF PRIMARY ALIPHATIC ALCOHOLS INTO HIGHER ALIPHATIC ALCOHOLS

Abstract

A process for obtaining higher aliphatic alcohols starting from aliphatic primary alcohols by condensation reactions is disclosed. Specifically, the process comprises a step in which an aliphatic primary alcohol is contacted in a homogeneous phase with a catalyst mixture comprising a transition metal, a base and an additive; specifically, this additive can be selected from the classes of compounds of the isoquinolines N-oxide, quinolines N-oxide, pyridines N-oxide, benzoquinones, naphthoquinones, or TEMPO. In particular, the process can be carried out by contacting said aliphatic primary alcohol with a catalyst of a recycled transition metal, with a freshly added base and with a recycled additive of the aforementioned type.

Claims

1. A process for the condensation of a primary aliphatic alcohol in a homogeneous phase comprising contacting said primary aliphatic alcohol with a catalyst mixture, wherein said catalyst mixture comprises: a) a catalyst comprising a complex of a transition metal of groups 7-11, wherein said transition metal is selected from the group consisting of Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt and Cu; b) a base; and c) an additive, wherein said additive is selected from any one of the classes of compounds of the group consisting of pyridines N-oxide, isoquinolines N-oxide, quinolines N-oxide, benzoquinones, naphthoquinones, TEMPO and derivatives thereof.

2. The process according to claim 1, wherein said additive belongs to the class of pyridines N-oxide or derivatives thereof and is a substituted pyridine N-oxide, said substituted pyridine N-oxide being substituted in position 2 and/or 3 and/or 4 with one or more substituents individually and independently selected from the group consisting of an aliphatic alkyl group, an aromatic group, halogen, hydroxyl, alkoxyl and a nitro group.

3. The process according to claim 1, wherein said additive is isoquinoline N-oxide, a substituted isoquinoline N-oxide or a substituted quinoline N-oxide, said substituted isoquinoline N-oxide or said substituted quinoline N-oxide being substituted in position 6 and/or 8 with one or more substituents individually and independently selected from the group consisting of an aliphatic alkyl group, an aromatic group, halogen, hydroxyl, alkoxyl and a nitro group.

4. The process according to claim 1, wherein said additive belongs to the class of benzoquinones or derivatives thereof and is 1,4-benzoquinone or a 2,6-disubstituted p-benzoquinone, said 2,6-disubstituted p-benzoquinone being substituted with substituents individually and independently selected from the group consisting of C2-C4 alkyl, C2-C4 alkoxyl, hydroxyl, amino and —NHCOR, wherein R═C2-C4 alkyl.

5. The process according to claim 1, wherein said additive belongs to the class of naphthoquinones and derivatives thereof and is a substituted naphthoquinone, said substituted naphthoquinone being substituted in position 2 and/or position 3 with one or more substituents individually and independently selected from the group consisting of an aliphatic alkyl group, hydroxyl, alkoxyl and halogen.

6. The process according to claim 1, wherein said additive belongs to the class of TEMPO or derivatives thereof and is TEMPO or substituted TEMPO, said substituted TEMPO being substituted in position 4 with a substituent selected from the group consisting of oxo, hydroxyl, alkoxyl, amino group, amide group, carboxyl group and ester group.

7. The process according to claim 1, wherein said primary aliphatic alcohol is a C2-C8 alcohol or any mixture thereof.

8. The process according to claim 1, wherein said catalyst comprising a complex of a transition metal of groups 7-11 comprises a ligand, said ligand being selected from any one of the classes of ligands of the group consisting of imidazolium salts, cyclopentadienones, cyclopentadienyls, carbonyl ligands, anionic ligands, ligands comprising an electron donor nitrogen, phosphine ligands, water, cyclooctadiene, aryl and a combination thereof.

9. The process according to claim 8, wherein said ligand is a ligand comprising an electron donor nitrogen and said ligand being an amine or a pyridine.

10. The process according to claim 8, wherein said ligand is a phosphine and said ligand being an alkyl phosphine or an aryl phosphine.

11. The process according to claim 8, wherein said ligand is an imidazolium salt, said imidazolium salt having the following general Formula I ##STR00007## R1 and R2 being substituents individually and independently selected from the group consisting of hydrogen, C1-05 alkyl and aryl; and X being chlorine, bromine or iodine.

12. The process according to claim 11, wherein said imidazolium salt is 1,3-dimethylimidazolyium chloride, 1,3-dimethylimidazolyium bromide or 1,3-dimethylimidazolyium iodide.

13. The process according to claim 8, wherein said catalyst comprising a complex of a transition metal of groups 7-11 is a complex having the following general
Formula II
[L′][Ru(CO).sub.2(L″)(η.sup.4-Ar)]  II L′ being a cation of the imidazolium or any substituted derivative thereof, L″ being halogen and Ar being aryl.

14. The process according to claim 1, wherein said catalyst is present in an amount lower than or equal to 1% by moles on the total moles of said primary aliphatic alcohol.

15. The process according to claim 1, wherein said additive is present in an amount between 0.5% and 5% by moles on the total moles of said primary aliphatic alcohol.

16. The process according to claim 1, wherein said base is selected from the group consisting of alkali or alkaline earth metal hydroxides, alkali or alkaline earth metal alkoxides and any combination thereof.

17. The process according to claim 1, wherein said base is present in an amount between 2% and 50% by moles on the total moles of said primary aliphatic alcohol.

18. The process according to claim 1, wherein said contacting of said primary aliphatic alcohol with a catalyst mixture is carried out at a temperature between 80° C. and 170° C.

19. The process according to claim 1, wherein said contacting said primary aliphatic alcohol with a catalyst mixture is carried out for a time between 5 minutes and 24 hours.

20. The process according to claim 1 further comprising: recycling said catalyst and said additive, obtaining a recycled catalyst and a recycled additive; adding said base to said recycled catalyst and said recycled additive, obtaining a recycled catalyst mixture; and contacting said primary aliphatic alcohol with said recycled catalyst mixture.

Description

DETAILED DESCRIPTION

[0073] The present invention therefore relates to a condensation process in a homogeneous phase of a primary aliphatic alcohol comprising the step of contacting such primary aliphatic alcohol with a catalyst mixture, wherein such catalyst mixture comprises:

a) a catalyst comprising a complex of a transition metal of groups 7-11, wherein said transition metal is selected from the group consisting of Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt and Cu;
b) a base;
c) an additive, wherein said additive is selected from any one of the classes of compounds of the group consisting of, isoquinolines N-oxide, quinolines N-oxide, pyridines N-oxide, benzoquinones, naphthoquinones, TEMPO and derivatives thereof.

[0074] As anticipated in the summary, the catalyst comprising a complex of a transition metal of groups 7-11, which in its turn comprises a ligand selected from any one of the classes of ligands of the group consisting of imidazolium salts, cyclopentadienones, cyclopentadienyls, carbonyl ligands, anionic ligands, ligands comprising at least one donor nitrogen, phosphine ligands, water, cyclooctadiene, aryls, and a combination thereof.

[0075] More particularly, the catalyst comprising a complex of a transition metal of groups 7-11 can comprise, in a completely preferred way, any one of the complexes used in the same class of reactions (Guerbet's reaction) indicated in the following prior art patent documents: WO201531561, US20130116481, U.S. Pat. No. 9,266,807, JP2011136970, JP2011225454; US20100298613, JP2008266267, JP2008303160, and JP2007223947.

[0076] In fact, first of all, the process according to the present invention allows to convert a primary aliphatic alcohol into a higher aliphatic alcohol by adding an additive of the aforementioned type to any one of the catalyst mixtures disclosed in the prior art shown in the previous paragraph and comprising a transition metal and a base-based complex. This conversion allows a high yield towards the linear dimer of such primary aliphatic alcohol (when ethanol is used as starting material) and other valuable higher alcohols showing a high flexibility in terms of application to different complexes of transition metals of the aforementioned additives.

[0077] Moreover, as anticipated in the summary with reference to the prior art cited in the paragraph relating to the background art, the present invention allows the conversion of a primary aliphatic alcohol into higher aliphatic alcohols (n-butanol as main product, starting from ethanol) with a rate much higher than the one of known transformations carried out in the sole presence of a catalyst comprising a complex of a transition metal of groups 7-11 and of a base, carrying out this transformation in the presence of the same catalyst comprising a complex of a transition metal of groups 7-11 and of the same base, but with the addition of an additive of the aforesaid type.

[0078] The present invention will be illustrated below with reference to some examples given by way of non-limiting example.

Example 1: Synthesis of a Ruthenium Complex

[0079] With reference to the following Scheme 2, 0.037 g of 1,3-dimethylimidazolium iodide (compound 1a in Scheme 2, 0.166 mmol) were reacted with 0.100 g (0.083 mmol) of dicarbonyl(η.sup.4-3,4-bis(4-methoxyphenyl)-2,5-diphenylcyclopenta-2,4-dienone) ruthenium dimer (compound 2 in Scheme 2) in a solution of CH.sub.2Cl.sub.2.

[0080] The reaction mixture was left under stirring at room temperature for 30 minutes.

[0081] By precipitation with a dichloromethane/n-hexane mixture, a yellow solid was obtained, identified as [dicarbonyl(η.sup.4-3,4-bis (4-methoxyphenyl)-2,5-diphenylcyclopenta-2,4-dienone)(iodine)ruthenium][1,3-dimethylimidazolium](Complex 3a in Scheme 2).

[0082] Complex 3a is stable to air, humidity and dissolved in a solution of non-anhydrous organic solvents.

##STR00003##

[0083] Analysis by infrared spectroscopy, proton NMR analysis (.sup.1H-NMR), carbon NMR analysis (.sup.13C-NMR), mass spectroscopy analysis (ESI-MS), and elemental analysis confirmed the formation of the Complex 3a. The results of the aforementioned analyzes are shown below.

[0084] .sup.1H-NMR (599.7 MHz, CDCl.sub.3): δ 9.91 (s, NCHN), 7.58-6.55 (m, 18H, CH.sub.aryl), 7.07 (s, 2H, CH.sub.im), 3.75 (s, 6H, NCH.sub.3), 3.70 (s, 6H, —OCH.sub.3).

[0085] .sup.13C-NMR (150.8 MHz, CDCl.sub.3, g-HSQC, g-HMBC, DEPT): δ 201.00 (CO), 172.12 (C═O, Cp), 158.40 (—COCH.sub.3), 138.96 (NCHN), 135.21-112.66 (C.sub.aryl), 122.55 (CH.sub.im), 100.09 (C.sub.2,5, Cp), 81.40 (C.sub.3,4, Cp), 55.01 (—OCH.sub.3), 36.55 (NCH3).

[0086] IR (CH.sub.2Cl.sub.2, cm.sup.−1): 2004, 1944 (ν.sub.CO); 1580 (ν.sub.C═O), 1604, 1518 (ν.sub.C═C).

[0087] ESI-MS (m/z) (+): 97 [M]+; (−): 729 [M]−.

[0088] Analysis calculated in percentage (%) for C.sub.38H.sub.33IN.sub.2O.sub.5Ru: C, 55.28; H, 4.03; N, 3.39.

[0089] Found: C, 55.26; H, 4.00; N, 3.41.

Example 2: General Procedure for the Conversion of Ethanol to n-Butanol and Higher Alcohols

[0090] With reference to Scheme 3 below, a 6 mL Schlenk was loaded with 14 mg of the ruthenium complex (Complex 3a in Scheme 2, 0.0172 mmol) synthesized in the previous example (Example 1), with a suitable amount of sodium ethoxide (NaOEt, 122 mg, 1.72 mmol) and with a suitable amount of additive (2,6-dimethoxybenzoquinone, 22 mg, 0.129 mmol).

[0091] Subsequently, 0.5 mL of ethanol (8.6 mmol) were added under inert atmosphere to the reaction mixture (the amount of Ru complex on the reagent is 0.2% molar).

[0092] Then, the resulting suspension was heated at 150° C. for 4 hours.

[0093] At the end of the reaction, the mixture was cooled to room temperature and then stored for 10 minutes in the refrigerator (temperature 4° C.).

##STR00004##

[0094] Finally, the mixture was diluted with 3 mL of Et.sub.2O and 162 μL of THF were added as an internal standard. The resulting mixture was analyzed by gas chromatography and gas chromatography interfaced with mass spectrometry.

[0095] Table 1 below shows the molar amounts of the base and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the ethanol conversion rate, the n-butanol yield, the total yield in alcohols, and the calculated carbon loss (loss).

TABLE-US-00001 TABLE 1 Alco- EtOH BuOH hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 A 1.5 150 4 72.1 37.5 61.0 11.1 A = 2,6-dimethoxybenzoquinone

[0096] Table 1 shows a high conversion and an equally high yield in n-butanol. The selectivity of the reaction with respect to the formation of n-butanol was calculated as follows.

[00001]$\mathrm{Selectivity}=\frac{\mathrm{yield}}{\mathrm{conversion}}*100$$\mathrm{wherein}$$\mathrm{Yield}=\left(n_{\mathrm{molCx}}*x/2\right)/n_{\mathrm{molEtOHin}}$

wherein n.sub.molCx corresponds to the number of moles of a given obtained higher aliphatic alcohol Cx for which the yield has to be calculated, e.g. n-butanol; wherein x corresponds to the number of carbon atoms of such higher aliphatic alcohol; and, wherein n.sub.molEtOHin corresponds to the number of moles of ethanol added to the reaction mixture.

[0097] In this case,

BuOH yield=(n.sub.molBuOH(C4)*4/2)/n.sub.molEtOHin

[0098] Thus, in the present example a selectivity equal to 51.6% is obtained, which is a better result than the selectivity calculated by the same formula for the same reaction from the data obtained from the document (D. Milstein et al. J. Am. Chem. Soc. 2016, 138, 9077-9080), with reference to the prior art, equal to 48.5%.

Example 3

[0099] The procedure reported in the Example 2 above was repeated varying the type of the used base.

[0100] The following Table 2 shows the molar amounts of the base, and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the ethanol conversion rate, the n-butanol yield, the total yield in alcohols, and the calculated carbon loss (loss); at first row, the results of Example 2 are given by way of comparison, at second and third rows, the results obtained using sodium hydroxide and sodium methoxide are respectively given.

TABLE-US-00002 TABLE 2 Alco- EtOH BuOH hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 A 1.5 150 4 72.1 37.5 61.0 11.1 NaOH 20 A 1.5 150 4 82.8 32.8 59.6 23.1 NaOMe 20 A 1.5 150 4 79.6 27.2 58.3 21.2 A = 2,6-dimethoxybenzoquinone

[0101] The results show that sodium hydroxide and sodium methoxide are also good candidates as bases to be used in the process of the invention, with particular attention to sodium hydroxide.

[0102] In particular, higher conversion values are observed with corresponding lower loss values. The overall alcohols yield remains constant.

Example 4

[0103] The procedure reported in Example 2 above was repeated varying the amount of additive used; in addition, p-benzoquinone as an additive was used instead of 2,6-dimethoxybenzoquinone.

[0104] The following Table 3 shows the molar amounts of the base and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the ethanol conversion rate, the n-butanol yield, the total yield in alcohols, and the calculated carbon loss (loss).

TABLE-US-00003 TABLE 3 Alco- EtOH BuOH hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 B 0.5 150 4 72.4 39.0 61.9 10.4 NaOEt 20 B 1.5 150 4 79.0 39.3 62.7 9.4 NaOEt 20 B 5 150 4 64.4 39.3 59.4 5.1 B = p-benzoquinone

[0105] As can be seen from Table 3, p-benzoquinone is also a good candidate for use as an additive according to the process of the present invention. Compared to Example 2, the use of p-benzoquinone allows to obtain comparable or even better results. Furthermore, at row 1 it is shown how this type of additive is particularly effective even at relatively low amounts by moles compared to the moles of ethanol (0.5% moles of additive with conversion at 72.4% and selectivity towards n-butanol of 54%).

[0106] Also in this case, the selectivity towards n-butanol calculated with the aforesaid method reaches values higher than those of the background art.

Example 5

[0107] The procedure reported in Example 2 above was repeated varying the used base amount.

[0108] The following table shows the molar amounts of the base and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the ethanol conversion rate, the n-butanol yield, the total yield in alcohols, and the calculated carbon loss (loss); at third row, the results of Example 2 are reported for comparison, at first and second rows the results obtained using lower amounts of base.

TABLE-US-00004 TABLE 4 Alco- EtOH BuOH hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 0.5 A 1.5 150 4 14.5 0.6 3.1 11.4 NaOEt 10 A 1.5 150 4 61.2 33.3 51.1 10.1 NaOEt 20 A 1.5 150 4 72.1 37.5 61.0 11.1 A = 2,6-dimethoxybenzoquinone

[0109] From Table 4 it can be deduced that even using half base amount, satisfactory ethanol conversion values and corresponding n-butanol yields can be obtained.

Example 6

[0110] The procedure reported in Example 2 above was repeated varying the type of used additive.

[0111] Depending on the type of additive, appropriate amounts of the same additive and base were used. The reaction temperature and the reaction time were kept equal to those of all previous examples.

[0112] Table 5 below shows the molar amounts of the base and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the ethanol conversion rate, the n-butanol yield, the total yield in alcohols, and the calculated carbon loss (loss); at first row, the results of Example 2 are reported for comparison, at second row the results reported at second row of Table 3 (Example 4) are reported for comparison, at third row the results obtained using TEMPO and the results obtained at the fourth row using isoquinoline N-oxide.

TABLE-US-00005 TABLE 5 Alco- EtOH BuOH hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 A 1.5 150 4 72.1 37.5 61.0 11.1 NaOEt 20 B 1.5 150 4 79.0 39.3 62.7 9.4 NaOEt 10 C 5 150 4 54.4 27.9 36.6 7.6 NaOEt 20 D 5 150 4 62.5 32.2 49.3 13.2 A = 2,6-dimethoxybenzoquinone B = p-benzoquinone C = TEMPO D = isoquinoline N-oxide

[0113] The results show that TEMPO and isoquinoline N-oxide are good candidates, and so are the derivatives thereof, to be used in the process of the invention as additives.

[0114] Advantageously, the data shown at row 4 can be obtained with a reaction time of 20 minutes with comparable conversion values and yields.

Example 7

[0115] The procedure reported in Example 2 above was repeated. Then, the catalyst, i.e. the Ru complex, was recovered and so was the additive.

[0116] In particular, at the end of the condensation reaction of the primary aliphatic alcohol, the obtained products, i.e. n-butanol as main product, valuable higher alcohols and unreacted ethanol, were separated by vacuum distillation.

[0117] In this way the catalyst and the additive form a recovery mixture, comprising a recovery catalyst and a recovery additive, which can be re-used for a new condensation cycle after adding a freshly amount of base and a freshly added amount of ethanol.

[0118] A suitable amount of sodium ethoxide (NaOEt, 122 mg, 1.72 mmol) was then added to the recovered catalyst and recovered additive.

[0119] Subsequently, 0.5 mL of ethanol (8.6 mmol) were added under inert atmosphere to the reaction mixture (the amount of Ru complex with respect to the reagent is equal to 0.2% molar also during the recovery cycle).

[0120] Then, the resulting suspension was heated at 150° C. for 4 hours, performing a second recovery cycle for the transformation from ethanol to n-butanol with a catalyst.

[0121] At the end of the reaction, the mixture was cooled to room temperature and then stored for 10 minutes in the refrigerator (temperature 4C).

[0122] Table 6 below shows the molar amounts of the base and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the ethanol conversion rate, the n-butanol yield, the total yield in alcohols, and the calculated carbon loss (loss), obtained both for the first cycle (first row) and for the second recovery cycle (second row).

TABLE-US-00006 TABLE 6 Alco- EtOH BuOH hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 A 1.5 150 4 72.1 37.5 61 11.1 NaOEt 20 A 1.5 150 4 67.7 35.3 52.9 14.7 A = 2,6-dimethoxybenzoquinone

[0123] As can be seen from Table 6, in an extremely advantageous manner, the recycled catalyst (with the additive) keeps the same activity (for the only addition of the fresh base) as can be seen from the comparison with the data of Example 2 reported in row 1.

Example 8—Comparative Example

[0124] For comparative purposes, in accordance with a process not according to the invention, a transformation of ethanol into n-butanol and higher alcohols was carried out in the presence of the same Ru complex used in the procedure reported in Example 2 and following.

[0125] In particular, a 6 mL Schlenk was loaded with 14 mg of the ruthenium complex (Complex 3a in Scheme 2, 0.0172 mmol) synthesized as in Example 1, with an appropriate amount of sodium ethoxide (NaOEt, 122 mg, 1.72 mmol).

[0126] Subsequently, 0.5 mL of ethanol (8.6 mmol) were added under inert atmosphere to the reaction mixture (the amount of Ru complex on the ethanol used as reagent is 0.2% molar).

[0127] Then, the resulting suspension was heated at 150° C. for 4 hours.

[0128] At the end of the reaction, the mixture was cooled to room temperature and then stored for 10 minutes in the refrigerator (temperature of 4° C.).

[0129] Subsequently, the mixture was diluted with 3 mL of Et.sub.2O and 162 μL of THF were added as an internal standard. The resulting mixture was analyzed by gas chromatography and gas chromatography on mass spectrometry.

[0130] Finally, the procedure was reproduced using a half base amount (NaOEt, 61 mg, 0.86 mmol).

[0131] Table 7 below shows the molar amounts of the base and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the ethanol conversion rate, the n-butanol yield, the total yield in alcohols, and the calculated carbon loss (loss).

TABLE-US-00007 TABLE 7 Alco- EtOH BuOH hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 — — 150 4 45.6 31.6 42.2 3.2 NaOEt 10 — — 150 4 31.9 19.2 23.8 8.1

[0132] As evident from the aforementioned Table 7, both the ethanol conversion values and the n-butanol yield values are significantly lower than the ethanol conversion values and those of the n-butanol yield obtained by performing a procedure using an additive, but with the same type of catalyst, type and base amount, as well as equal reaction conditions, as reported in the Examples 2-5 above.

Example 9: General Procedure for the Conversion of Butanol to Higher Alcohols

[0133] With reference to Scheme 4 below, a 6 mL Schlenk was loaded with 8.9 mg of the ruthenium complex (Complex 3a in Scheme 4, 0.0108 mmol) synthesized in the previous Example 1, with a suitable amount of sodium ethoxide (NaOEt, 76 mg, 1.08 mmol) and with a suitable amount of additive (p-benzoquinone, 8.7 mg, 0.081 mmol).

[0134] Subsequently, 0.5 mL of butanol (5.4 mmol) were added under inert atmosphere to the reaction mixture (the amount of Ru complex on the reagent was 0.2% molar).

[0135] Then, the resulting suspension was heated at 150° C. for 4 hours.

[0136] At the end of the reaction, the mixture was cooled to room temperature and then stored for 10 minutes in the refrigerator (temperature: 4C).

##STR00005##

[0137] Finally, the mixture was diluted with 3 mL of Et.sub.2O and 162 μL of THF were added as an internal standard. The resulting mixture was analyzed by gas chromatography and gas chromatography interfaced with mass spectrometry.

[0138] Table 8 below shows the molar amounts of the base and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the butanol conversion rate, the 2-ethylhexanol yield, the total yield in alcohols, and the calculated carbon loss (loss).

TABLE-US-00008 TABLE 8 2-ethyl- Alco- BuOH hexanol hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 B 1.5 150 4 51.9 26.4 44.1 7.8 B = p-benzoquinone

[0139] Table 8 shows a satisfactory conversion and an equally satisfactory yield in 2-ethylhexanol.

Example 10

[0140] The procedure reported in the Example 9 above was repeated varying the type of the used base.

[0141] The following Table 9 shows the molar amounts of the base, and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the butanol conversion rate, the 2-ethylhexanol yield, the total yield in alcohols, and the calculated carbon loss (loss); at first row, the results of Example 9 are given by way of comparison, at second row, the results obtained using sodium hydroxide are given.

TABLE-US-00009 TABLE 9 2-ethyl- Alco- BuOH hexanol hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 A 1.5 150 4 51.9 26.4 44.1 7.8 NaOH 20 A 1.5 150 4 50.5 32.9 33.8 16.7 B = p-benzoquinone

[0142] Table 9 shows that sodium hydroxide is an effective base in the process according to the present invention when butanol is used as a reagent.

Example 11: General Procedure for the Conversion of 1-Hexanol to Higher Alcohols

[0143] With reference to Scheme 5 below, a 6 mL Schlenk was loaded with 6.4 mg of the ruthenium complex (Complex 3a in Scheme 5, 0.0078 mmol) synthesized in the previous Example 1, with a suitable amount of sodium ethoxide (NaOEt, 55 mg, 0.78 mmol) and with a suitable amount of additive (p-benzoquinone, 6.3 mg, 0.058 mmol).

[0144] Subsequently, 0.5 mL of hexanol (3.9 mmol) were added under inert atmosphere to the reaction mixture (the amount of Ru complex on the reagent was 0.2% molar).

[0145] Then, the resulting suspension was heated at 150° C. for 4 hours.

[0146] At the end of the reaction, the mixture was cooled to room temperature and then stored for 10 minutes in the refrigerator (temperature: 4° C.).

##STR00006##

[0147] Finally, the mixture was diluted with 3 mL of Et.sub.2O and 162 μL of THF were added as an internal standard. The resulting mixture was analyzed by gas chromatography and gas chromatography interfaced with mass spectrometry.

[0148] Table 10 below shows the molar amounts of the base and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the 1-hexanol conversion rate, the 2-butyl-1-octanol yield, the total yield in alcohols, and the calculated carbon loss (loss).

TABLE-US-00010 TABLE 10 2-butyl- Hex- 1- Alco- anol octanol hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 B 1.5 150 4 61.7 29.5 45.8 15.9 B = p-benzoquinone

[0149] Table 10 shows a satisfactory conversion and an equally satisfactory yield in 2-butyl-1-octanol.

Example 12

[0150] The procedure reported in the Example 11 above was repeated varying the type of the used base.

[0151] The following Table 11 shows the molar amounts of the base, and of the additive with respect to the alcohol, as well as the reaction temperature and the reaction time, the hexanol conversion rate, the 2-butyl-1-octanol yield, the total yield in alcohols, and the calculated carbon loss (loss); at first row, the results of Example 11 are given by way of comparison, at second row, the results obtained using sodium hydroxide are given.

TABLE-US-00011 TABLE 11 2-butyl- Hex- 1- Alco- anol octanol hols Base Add. T t Conv. yield yield Loss Base (%) Add. (%) (° C.) (h) (%) (%) (%) (%) NaOEt 20 A 1.5 150 4 61.7 29.5 45.8 15.9 NaOH 20 A 1.5 150 4 56.1 30.6 31.2 24.9 B = p-benzoquinone

[0152] Table 11 shows that sodium hydroxide is an effective base in the process according to the present invention when 1-hexanol is used as a reagent.