CS268278B1 - Process for the synthesis of 4-oxopentylalkanoates - Google Patents

Abstract

The solution relates to a method for the synthesis of 4-oxopentyl alkanoates of the general formula I, where R is hydrogen or alkyl with a carbon number of C. to C., by radical addition of acetaldehyde to allyl alkanoates of the general formula II, where R has the above-mentioned meaning, initiated by X-ray irradiation at temperatures of -25 to 30 °C for a period of time during which 40 to 100% of the starting allyl alkanoate reacts.

Description

The invention ee relates to a process for the synthesis of a 4-oxopentylalkanoate of general formula I, wherein R 1 is hydrogen or alkyl having a number of carbons up to C 4.

4-Oxopentylalkanoates, in particular 4-oxopentyl acetate (I, R-CH 2), are the starting materials for the preparation of 5-hydroxy-2-pentanone from which the drugs, vitamin B 1 and azonin initiators used to make teleohelical elastomers are prepared.

Existing methods for the synthesis of 4-oxopentylalkanoate of formula I, in particular 4-oxopentyl acetate (I, R CH 2) and 4-oxopentyl formate (I, R H), rely on the warm rearrangement of 3- (2-hydroxyethyl) -2,4-pentanedione (Huet J , Druex J .: Comt. -methyltetrahydrofuran in the presence of diacetyl or glyoxal (Glukhovtsev VG et al .: Ser. Khim. 2, 485 (1977)), Zh. Org. Khim. 17, 518 (1961)) and to the radial addition of acetaldehyde to allyl acetate initiated by dibenzoyl peroxide (Ladd EC: U.S. Pat. No. 2,533,944 (1950)) or initiated by oxygen in the presence of cobalt or manganese acetates (Vinogradov et al .: Izv. Akad. Nauk SSSR 322/1969 /) ', Zh. Prikl. Khim .: (Leningrad / 56, 467 (1983)).

Said processes for the synthesis of the 4-oxopentylalkanoates of the formula I are generally multistage syntheses with relatively low yields of the 4-oxopentylalkanoates of the formula I, which can be contaminated by the decomposition products of the initiators or the products of the photolysis of acetaldehyde.

The process for the preparation of 4-oxopentylalkanoates of the general formula I, in which R 1 is hydrogen or alkyl having a carbon number of C ₁ to C 4, according to the invention overcomes these drawbacks. Its essence lies in the fact that the solution of allylalkanoate of general formula II, where RH or alkyl of carbon number C. | to 5 to 100 molar excess of acetaldehyde is irradiated with 6 ° C at -25 to 30 ° C for as long as 40 to 60% of the starting alkyl alkanoate reacts. A sufficiently high molar ratio of acetaldehyde: allylalkanoate II guarantees a high yield of 1: 1 adducts, i.e. 4-oxopentylalkanoates of formula I at the expense of by-products of the addition of ~ 1: n telomeres of formula III, where RH or alkyl and carbon numbers up to a n- 2 After irradiation, the reaction mixture is worked up by distillation or rectification.

The effect of the process according to the invention is that the 4-oxopentyl acetates of the formula I are formed in relatively high yields by the radiation-initiated addition of acetaldehyde to the allylalkanoates of the formula II in relatively high yields. the free radical additions, the good separation of the reaction products of the formula I from the 1: n telomeres of the formula III and the fact that a number of by-products which are formed during the photolysis of acetaldehyde do not form during radiolysis.

The process according to the invention is further described in several exemplary embodiments.

Example 1

Allyl acetate (326.0 g, 3.256 mol) was dissolved in acetaldehyde (2869.0 g, 65.126 mol) and the resulting solution was purged with nitrogen in a glass flask and then irradiated with θΟο (42 kGy) at -30 to 25 ° C. After irradiation, the precipitated metal aldehyde was filtered off from the reaction mixture, m.p. 157-160 ° C (10.8 g). Unreacted acetaldehyde was distilled off from the filtrate, and paraldehyde formed. Rectification of the residue gave 236.5 g (50.4%) of 4-oxopentyl acetate (I, R-CH 2) boiling at 100-101 ° C / 1.7 kPa and 72.8 g (18.8%) of 7 -acetoxy-4-acetoxymethyl-2-heptanone (III, R «CH 2, n-2), b.p. 138-140 ° C (66.6 Pa).

CS 26-27 B1

Example 2

A mixture of allyl acetate (6.4 g, 0.063 mol) and acetaldehyde (112.6 g, 2.56 mol) was irradiated under a nitrogen atmosphere in a glass vial at room temperature with 6θO (100 kGy). Then the reaction mixture was worked up by rectification to give 7.67 g (83.25%) of 4-oxopentyl acetate (X, R-CH 2) boiling at 90-105 ° C / 1.6 kPa and 0.45 g (5 77%) 7-acetoxy-4-acetoxymethyl-2-heptanone (III, R-CH 2, n-2), b.p. 160-170 ° C / 120 Pa.

Example 3

A mixture of allyl formate (9.6 g, 0.112 mol) and acetaldehyde (98.0 g, 2.22 mol) was irradiated with a dose of ^ί ^ θ0ο (50 kGy). Rectification of the reaction mixture gave 8.86 g (61.0%) of 4-oxopentyl formate (I, RH) b.p. 89-90 ° C / 1.7 kPa and 1.77 g (14.7%) of 7-formyloxy -4-formyloxymethyl-2-haptanone (III, RH, n-2), b.p. 140-150 ° C / 133 Pa. .

Example 4

A mixture of allyl formate (280.0 g ', 3.252 mol) and acetaldehyde (2865 g', 65.03 mol) was irradiated with a dose of 42 kGy. The precipitated metaldehyde crystals were filtered off (11.6 g, m.p. 157-160 ° C), and unreacted acetaldehyde and paraldehyde formed were removed by distillation. Further rectification gave 213.6 g (50.5%) of 4-oxopentyl formate boiling at 80-85 ° C / 1.6 kPa and 58.3 g (16.6%) of 7-formyloxy-4-phenyloxymethyl-2 -heptanone (III, RH, n-2) boiling at 140-150 ° C / 133 Pa.

Claims (1)

OBJECT OF THE INVENTION Process for the synthesis of 4-oxopentylalkanoates of general formula X, wherein R is hydrogen or alkyl of carbon numbers C ₁ to C 2, characterized in that a solution of allylalkanoate of general formula XI, wherein R H or alkyl of carbon numbers C ₁ to 5 to 100 molar excess of acetaldehyde is irradiated with ΊΓ-Co radiation at -25 to 30 ° C for a time during which 40 to 100% of the starting allylalkanoate reacts.