JPS6338974B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing acetals from carbonyl compounds.

Acetals are generally produced by reacting carbonyl compounds with alcohols or esters in the presence of brended acid; however, unlike these conventional methods, the present invention is a novel method for producing acetals from carbonyl compounds and alkoxysilanes. be. The novel method for producing acetals of the present invention proceeds under mild conditions and in high yields by using trialkylsilyl trihalomethanesulfonate as a catalyst, but it also proceeds using common Lewis acids.

As the method of the present invention, for example, in an inert gas atmosphere,
One method is to add a carbonyl compound and an alkoxysilane to an organic solvent containing a catalyst trialkylsilyl trihalomethanesulfonate at a low temperature, react with stirring for several hours, and then inject this into an aqueous alkali solution. After the reaction is completed, the acetal produced from the product mixture is extracted with an extractant such as diethyl ether, the extracted product is further dried, and the extractant is removed to isolate the product acetal.

Carbonyl compounds to which the present invention is applicable are aldehydes and ketones. Specifically, cyclopentanone, cyclohexanone, cyclododecanone,
3-cyclopentenone, 2-cyclohexenone,
Alicyclic ketones such as 3-cyclohexenone, 2-cyclododecenone, aliphatic ketones such as acetone, methyl ethyl ketone, mesityl oxide, 4-methyl-3-penten-2-one, 2-octenone, benzophenone, acetophenone, Aromatic ketones such as propiophenone, aromatic aldehydes such as benzaldehyde, cinnamaldehyde, acetaldehyde, butyraldehyde,
Examples include aliphatic aldehydes such as octylaldehyde and crotonaldehyde, and alicyclic aldehydes such as cyclopentylaldehyde, cyclohexylaldehyde, and cyclohexenylaldehyde.

The alkoxysilanes used in the present invention include methoxytrimethylsilane, benzoxytrimethylsilane, benzyloxytrimethylsilane, 1,2-
These include bistrimethylsiloxyethane and 1,3-bistrimethylsiloxypropane. The alkoxysilane is used in roughly stoichiometric amounts relative to the carbonyl compound.

The organic solvent used in the present invention is preferably a halogenated hydrocarbon such as dichloromethane, dibromoethane, trichloroethane, dichloroethane, chloroform, carbon tetrachloride.

As the trialkylsilyl trihalomethanesulfonate used in the present invention, trimethylsilyltrifluoromethanesulfonate, trimethylsilyldifluoromethanesulfonate, etc. are preferable. The amount of trialkylsilyl trihalomethanesulfonate used may be a catalytic amount, and is about 0.05 to 10% based on the carbonyl compound.

The reaction temperature is preferably -80°C to 25°C,
The reaction is carried out under an inert gas atmosphere.

According to the present invention, benzaldehyde dimethyl acetal, cyclohexanone dimethyl acetal, cyclopentanone dimethyl acetal, acetaldehyde dimethyl acetal, 2-cyclohexenone ethylene acetal, 3-cyclopentenone dimethyl acetal, etc. can be easily produced.

The present invention is a method for producing acetal based on a novel reaction, and this novel method is significant in that it has discovered the use of alkoxysilane as an acetalizing agent for carbonyl compounds, and is a driving force behind the production of stable hexamethylsiloxane. This is a new method. Furthermore, this new method has the advantage of proceeding smoothly and in high yield under aprotic conditions and relatively mild conditions by using trialkylsilyl trihalomethanesulfonate as a catalyst.

Example 1 1 ml (22 mg, 0.1 mmol, 1 mol%) of a 0.1 mol dichloromethane solution of trimethylsilyltrifluoromethanesulfonate was placed in a container purged with argon. After cooling to −78° C., methoxytrimethylsilane (2.13 g, 20.5 mmol) and then cyclohexanone (1.02 g, 10.4 mmol) were added via syringe. After stirring at -78℃ for 3 hours, anhydrous pyridine (0.2
ml) was added at -78°C. The reaction mixture was poured into saturated sodium bicarbonate water (15 ml) and extracted with ether (20 ml).
×3). After drying the organic layer with sodium sulfate and sodium carbonate, the solvent was removed under reduced pressure. Cyclohexanone dimethyl acetal (1.31 g, 89%) was obtained as a colorless liquid by bulb distillation of the reaction crude product, bp 130-145°C/104 mmHg. This product was identified by comparison with a separately synthesized standard using NMR spectra and TLC.

Example 2 1 ml of a 0.1 mol dichloromethane solution of trimethylsilyltrifluoromethanesulfonate (22 mg, 0.1 mmol, 1 mol %) was placed in a container purged with argon. The mixture was cooled to −78° C., and 1,2-bistrimethylsiloxyethane (2.06 g, 10.0 mmol) and then cyclohexanone (960 mg, 9.9 mmol) were added using a syringe. After stirring at -78°C for 4 hours, anhydrous pyridine (0.2ml) was added at -78°C. The reaction mixture was poured into saturated sodium bicarbonate water (15 ml) and extracted with ether (20 ml x 3). After drying the organic layer with sodium sulfate-potassium carbonate, the solvent was removed under reduced pressure. Cyclohexanone ethylene acetal (1.33 g, 96%) was obtained by bulb distilling the reaction crude product.
obtained as a colorless liquid, bp135-150℃/98mm
Hg. This product was identified by comparison with a separately synthesized standard using NMR spectra and TLC.

Example 3 0.5 ml (11 mg, 0.05 mmol, 1 mol%) of a 0.1 mol dichloromethane solution of trimethylsilyltrifluoromethanesulfonate was placed in a container purged with argon. The mixture was cooled to −78° C., and benzyloxytrimethylsilane (1.78 g, 9.9 mmol) and then cyclohexanone (525 mg, 5.4 mmol) were added via syringe. After stirring at −78°C for 20 hours, anhydrous pyridine (0.25
ml) was added at -78°C. The reaction mixture was poured into saturated sodium bicarbonate water (15 ml) and extracted with ether (20 ml).
ml x 3). After drying the organic layer with sodium sulfate-potassium carbonate, the solvent was removed under reduced pressure (1 mmHg) to obtain cyclohexanone diverdyl acetal (1.44 g, 99%) as a colorless liquid.

Γ NMR ( _CCl4 , No.3072); δ1.2~1.9 (10H, ring
protons), 4.45 (4H, S, -OCH ₂ ), and 7.22
(10H, S, -C ₆ H ₅ ) Γ IR (neat); 1082 (C-O), 720 (-C ₆ H ₅ ),
and 692cm ^-1 (−C ₆ H ₅ ) Γ Mass; m/e296 (M ⁺ , 1%), 205 (24%),
99 (13%), and 91 (100%) Γ R _f =0.59 (benzene) Example 4 1 ml (22 mg, 0.1 mmol, 1 mol%) of a 0.1 mol dichloromethane solution of trimethylsilyltrifluoromethanesulfonate was placed in a container purged with argon. . The mixture was cooled to −78° C., and methoxytrimethylsilane (2.08 g, 20.0 mmol) and then cyclopentanone (806 mg, 9.6 mmol) were added via syringe.
After stirring at -78℃ for 3 hours, anhydrous pyridine (0.2ml)
was added at -78°C. The reaction mixture was poured into saturated sodium bicarbonate water (15 ml) and extracted with ether (20 mol
3). After drying the organic layer with sodium sulfate and potassium carbonate, the solvent was removed under reduced pressure. Cyclopentanone dimethyl acetal (983 mg, 79%) was obtained as a colorless liquid by bulb distillation of the reaction crude product, bp 140-150°C/760mmHg. This product was identified by comparison with a separately synthesized standard using NMR spectra and TLC. In addition, the reaction crude product contains 90%
The presence of acetal was determined by NMR.

Example 5 1 ml of a 0.1 mol dichloromethane solution of trimethylsilyltrifluoromethanesulfonate (22 mg, 0.1 mmol, 1 mol %) was placed in a container purged with argon. The mixture was cooled to −78° C., and methoxytrimethylsilane (2.11 g, 20.0 mmol) and then benzaldehyde (1.07 g, 10.0 mmol) were added via syringe. After stirring at -78℃ for 3 hours, anhydrous pyridine (0.2
ml) was added at -78°C. The reaction mixture was poured into saturated sodium bicarbonate water (15 ml) and extracted with ether (20 ml).
×3). After drying the organic layer with sodium sulfate and sodium carbonate, the solvent was removed under reduced pressure. Benzaldehyde dimethyl acetal (1.45 g, 94%) was obtained as a colorless liquid by bulb distillation of the reaction crude product, bp 125-135°C/51 mmHg. This product was identified by comparison with a separately synthesized standard using NMR spectra and TLC.

Example 6 In a container purged with argon, 0.5 ml of a 0.1 mol dichloromethane solution of trimethylsilyl triflate (11
mg, 0.05 mmol, 1 mol%). The mixture was cooled to −78° C., and 1,2-bistrimethylsiloxyethane (1.04 g, 5.1 mmol) and then 2-cyclohexenone (519 mg, 5.4 mmol) were added using a syringe. −
After stirring at 78°C for 20 hours, anhydrous pyridine (0.2ml) was added at -78°C. The reaction mixture was poured into saturated sodium bicarbonate water (15 ml) and extracted with ether (20 ml x
3). After drying the organic layer with sodium sulfate and sodium carbonate, the solvent was removed under reduced pressure. 2-Cyclohexenone ethylene acetal (651 mg, 92%) was obtained as a colorless liquid by bulb distillation of the reaction crude product, bp 120-130°C/98mmHg. This product was identified by comparison with a separately synthesized standard using NMR spectra and TLC.

Example 7 0.5 ml (11 mg, 0.05 mmol, 1 mol%) of a 0.1 mol dichloromethane solution of trimethylsilyltrifluoromethanesulfonate was placed in a container purged with argon. The mixture was cooled to −78° C., and 1,2-bistrimethylcyclooxyethane (1.05 g, 5.0 mmol) and then 3-cyclohexenone (482 mg, 5.0 mmol) were added using a syringe. -78℃ for 3 hours and then -20℃
After stirring for 0.2 h at
Added at ℃. The reaction mixture was diluted with saturated sodium hydrogen aqueous solution (15
ml) and extracted with ether (20 ml x 3).
After drying the organic layer with sodium sulfate and sodium carbonate, the solvent was removed under reduced pressure. 3-Cyclohexenone ethylene acetal (707 mg, 99%) was obtained as a colorless liquid by bulb distillation of the reaction crude product, bp 90-100°C/89mmHg. This one is NMR
(identified by comparing spectra with literature values).

Example 8 0.5 ml (11 mg, 0.05 mmol, 1 mol%) of a 0.1 mol dichloromethane solution of trimethylsilyltrifluoromethanesulfonate was placed in a container purged with argon. The mixture was cooled to −78° C., and 1,2-bistrimethylsiloxane (1.05 g, 5.0 mmol) and then 3-cyclopentenone (404 mg, 4.9 mmol) were added using a syringe. After stirring at -78°C for 4 hours, anhydrous pyridine (0.2ml) was added at -78°C. The reaction mixture was poured into saturated sodium hydrogen chloride water (15 ml) and extracted with pentane (30 ml x 3). After drying the organic layer with sodium sulfate and sodium carbonate, the solvent was removed under reduced pressure. Bulb distillation of the reaction crude product yielded 3-cyclopentenone ethylene acetal (585 mg, 94%).
was obtained as a colorless liquid, bp60℃/30mmHg.

Γ NMR (CCl ₄ , No. 3104); δ 2.41 (4H, S, −
C H ₂ C=C), 3.77 (4H, S, -OC H ₂ C H ₂ O
-), and 5.55ppm (2H, S, -C H = C H -) Γ IR (neat); 1090 cm ^-1 (C-O) Γ Mass; m/e 126 (M ⁺ , 100%), 99 ( twenty three
%), 82 (19%), 66 (8%) and 54 (31%) Γ R _f =0.21 (benzene)

Claims (1)

[Scope of Claims] 1. A method for producing an acetal, which comprises reacting a carbonyl compound selected from alicyclic ketones and aromatic aldehydes with an alkoxysilane using a catalyst trialkylsilyltrihalomethanesulfonate. 2. The method according to claim 1, wherein the carbonyl compound is an alicyclic ketone. 3. The method according to claim 1, wherein the carbonyl compound is an aromatic aldehyde. 4. The method according to claim 1, wherein the alkoxysilane is methoxytrimethylsilane. 5 Claim 1 characterized in that the alkoxysilane is benzoxytrimethylsilane
The method described in section. 6. The method according to claim 1, wherein the alkoxysilane is 1,2-bistrimethylsiloxyethane. 7. The method according to claim 1, wherein the trialkylsilyl trihalomethanesulfonate is trimethylsilyltrifluoromethanesulfonate.