CS268322B1 - Process for preparing 5-hydroxy-2-pentanone - Google Patents

Abstract

The solution relates to a method for preparing 5-hydroxy-2-pentanone of formula I by radical addition of acetaldehyde to allyl alcohol of formula III initiated by ultraviolet and/or ^'-radiation θθΟο at a temperature of - 25 to 30 °C for a period of time during which 40 to 100% of allyl alcohol reacts and the reaction mixture is optionally subjected to a reaction with water at a temperature up to the boiling point of the reaction mixture

Description

The invention relates to a process for the preparation of 5-hydroxy-2-pentanone of formula I

5-Hydroxy-2-pentanone of formula I It is an important intermediate in organic synthesis. De starting material for the manufacture of drugs, vitemine Bia ezoinitiators needed for the synthesis of telechelic polymers.

Prior art processes for the preparation of 5-hydroxy-2-pentanone of the formula I are based on ethyl acetoacetate (Knunjantz IL, GW head, Ossetrova ED: Dokl. Akad. Nauk 4, 314 (1934)), 2-methylfuran (Grigariev AA et al., Khim. Farm.Zh.9, 37 (1975), Beloslynd's TM, Ilina LA: Zh. No. 2,533,944 (1950)) or oxygen and the presence of cobalt or manganese acetates (Vinogradov et al .: Izv. Akad. Nauk SSSR 1969. 322; Zh. Prikl. Khim. / Leningrad / 56, 467./1983/

Said processes for the preparation of 5-hydroxy-2-pantanone of the formula I are generally multi-step syntheses, the reaction products are contaminated with initiator decomposition by-products or the 5-hydroxy-2-pentanone of the formula I must be liberated by acidic or alkali-catalyzed reesterification. .

The process for the preparation of 5-hydroxy-2-pantanone of the formula I according to the invention overcomes these drawbacks. Its essence is that a solution of the allyl alcohol of formula III in a 5 to 100 molar excess of acetaldehyde is irradiated with ultraviolet and / or ®Co radiation at -25 to -30 ° C for a time during which 40 to 100% of the allyl alcohol reacts and the reaction mixture is optionally reacted with water to the boiling point of the reaction mixture. The reaction is carried out by dissolving the allyl alcohol of the formula III in an excess of acetaldehyde and irradiating the resulting solution with ultraviolet radiation, preferably a mercury lamp at temperatures of -25 to -30 DEG C. and / or Oe radiation, when the molar ratio of acetaldehyde: allyl alcohol of formula III is 5 to 100: 1, preferably then 20 to 60: 1.

A sufficiently high molar ratio of acetaldehyde: allyl alcohol III guarantees a high yield of 5-hydroxy-2-pentanone of formula I and / or its mixture with 2- (4-oxopontyloxy) -2-methyltetrahydrofuranes of formula II to the detriment of the formation of by-products of the -7-hydroxy edition. -4-hydroxymethyl-2-heptanone of formula IV (n »2) and higher telomeres of general formula IV. The reaction mixture after irradiation is worked up by distillation and / or rectification. Photochemically and / or radiation-initiated addition of acetaldehyde to the allyl alcohol of formula III gives 5-hydroxy-2-pentanone of formula I in relatively high yields.

2- (4-oxopentyl) -2-methyltetrahydrofuran of formula II, which accompanies hydroxypentanone of formula I, is the product of the interaction of hydroxypentanone of formula I with its teutomeric form, i.e. 2-hydroxy-2-methyltetrahydrofuran of formula V. Tetrahydrofuran of formula II undergoes short-term heating in aqueous solution to the hydroxypentenone of the formula I and / or this conversion takes place in a further reaction step using the synthetic use of the hydroxyketone of the formula I.

The advantages of the process according to the invention are the relatively easy availability of acetaldehyde and allyl alcohol, the simple radical addition itself, the good separation of 5-hydroxy-2-pentanone of formula I and 2- (4-oxopentyloxy) -2-methyltetrahydrofuran of formula II from excess acetaldehyde and optionally unreacted allyl alcohol. , as well as from reaction by-products, of the telomeres of general formula IV; the regenerated acetaldehyde can be returned to the reaction.

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

Example 1

A solution of allyl alcohol (4.27 g; 0.074 mol) in acetaldehyde (62.7 g; 1.42 mol) was irradiated for 9 hours under argon in a photochemical reactor with a Tesle RVK 125 mercury lamp. The temperature of the reaction mixture was kept between 15 to 17 ° C. Unreacted acetaldehyde was removed by distillation of the reaction mixture and further distillation gave 2.90 g of a fraction boiling at 84-100 ° C / 1.6 kPa, which was identified by a 1 H-NMR spectrum as a mixture of hydroxypentanone of formula I and tetrahydrofuran derivative of formula II. , represented in the ratio 35: 65.

Example 2

Allyl alcohol (3.5 g; 0.06 mol) was dissolved in acetaldehyde (106.2 g; 2.41 mol) and the resulting solution was purged with nitrogen in an agglomerated ampoule and sealed. The reaction mixture was

- 2 - CS 268 322 B1 irradiated with a dose of 110 kGy ^ radiation of ⁶⁰ Co. After irradiation, the reaction mixture was analyzed by thin layer chromatography (silica gel G, CHCl 3 ♦ 5 X CH 2 OH) and the presence of 5-hydroxy-2-pentanone of formula I, 2- (4-oxopentyloxy) -2-hydroxytetrahydrofuran of formula II and 1: 2 teloasr of formula IV (η · 2). Excess acetaldehyde was distilled off from the reaction mixture and 4.6 g (79%) of a fraction at 80 DEG-112 DEG C./2 kPa was obtained by further distillation, which was identified by 1 H-NMR as a mixture of hydroxypentanone of the formula I and tetrahydrofuran of the formula I. II represented in a ratio of about 50: 50 ·

Example 3

A solution of allyl alcohol (6.5 g; 0.112 mol) in acetaldehyde (98.6 g; 2.24 mol) was irradiated in a sealed glass capsule with a dose of 110 kGy. Unreacted acetaldehyde was removed by distillation, and further distillation gave 7.1 g (68%) of a fraction boiling at 85-112 DEG C./2 kPa, which was identified by NMR as a mixture of hydroxypentanone of formula I and tetrahydrofuran of formula II represented in a ratio of 50:50.

Claims (1)

OBJECT OF THE INVENTION Process for the preparation of 5-hydroxy-2-pentanone of the formula I, characterized in that ae solution of the allyl alcohol of the formula III in a 5 to 100 molar excess of acetaldehyde is irradiated with ultraviolet and / or 50 ° C radiation at -25 to 30 ° C for a time which 40 to 100% of the allyl alcohol is reacted and the reaction mixture is optionally reacted with water at a temperature up to the boiling point of the reaction mixture.