Process for preparing pentenoate

Abstract

The invention pertains to a process for preparing a compound of formula (1) ##STR00001## wherein R.sub.1 is independently chosen from C.sub.1-C.sub.6 alkyl, cycloalkyl, aralkyl and aryl, and R.sub.2, R.sub.3 and R.sub.4 are independently chosen from hydrogen and C.sub.1-C.sub.6 alkyl, cycloalkyl, aralkyl and aryl; which process comprises the steps of: a) contacting a compound of formula (2) ##STR00002## wherein R.sub.1 and R.sub.2 are as above and M.sup.+ is a monovalent metal ion, with a compound of formula (3) ##STR00003## wherein R.sub.3 and R.sub.4 are as above, to form a compound of formula (4) ##STR00004##
and b) followed by contacting the compound of formula (4) with an acid to give a compound of formula (1), wherein step (a) and/or step (b) are conducted in continuous mode.

Claims

1. A process for preparing a compound of formula (1) ##STR00015## wherein R.sub.1 is independently chosen from C.sub.1-C.sub.6 alkyl, cycloalkyl, aralkyl and aryl, and R.sub.2, R.sub.3 and R.sub.4 are independently chosen from hydrogen and C.sub.1-C.sub.6 alkyl, cycloalkyl, aralkyl and aryl; which process comprises the steps of: a) contacting a compound of formula (2) ##STR00016## wherein R.sub.1 and R.sub.2 are as above and M.sup.+ is a monovalent metal ion, with a compound of formula (3) ##STR00017## wherein R.sub.3 and R.sub.4 are as above, to form a compound of formula (4) ##STR00018## and b) followed by contacting the compound of formula (4) with an acid to give a compound of formula (1), wherein step (a) and/or step (b) are conducted in continuous mode.

2. The process according to claim 1, wherein the compound of formula (2) is formed by the step of (c) contacting a compound of formula (5) ##STR00019## with a base.

3. The process according to claim 2, wherein step (c) is conducted in continuous mode.

4. The process according to claim 1, wherein the compound of formula (3) is formed by the step of: (d) dehydration of a compound of formula (6) ##STR00020## in the presence of an acid catalyst.

5. The process according to claim 4, wherein step (d) is conducted in continuous mode.

6. A process for preparing the compound of formula (2) ##STR00021## wherein R.sub.1 is independently chosen from C.sub.1-C.sub.6 alkyl, cycloalkyl, aralkyl and aryl, and R.sub.2 is independently chosen from hydrogen and C.sub.1-C.sub.6 alkyl, cycloalkyl, aralkyl and aryl; and wherein the process comprises the step of (a) contacting a compound of formula (5) ##STR00022## with a base, wherein the base is lithium diisopropyl amide formed in situ from diisopropyl amine and n-butyl lithium, and wherein step (a) is conducted in continuous mode.

7. The process according to claim 2, wherein the compound of formula (3) is formed by the step of: (d) dehydration of a compound of formula (6) ##STR00023## in the presence of an acid catalyst.

8. The process according to claim 3, wherein the compound of formula (3) is formed by the step of: (d) dehydration of a compound of formula (6) ##STR00024## in the presence of an acid catalyst.

9. The process according to claim 7, wherein step (d) is conducted in continuous mode.

10. The process according to claim 8, wherein step (d) is conducted in continuous mode.

Description

(1) A brief description of the FIGURES is given below.

(2) FIG. 1: set-up for production of pentenoate (1) with R.sub.1=tert. butyl and R.sub.2R.sub.3R.sub.4H including flow rates of the pumps as well as the inner diameter of the tubes.

(3) The invention is exemplified in the following Examples.

EXAMPLES

Example 1

Continuous Synthesis of Acrolein from Glycerol

(4) In a continuous stirred tank reactor are placed 14 g glycerol, 40 g KHSO.sub.4 and 8 g K.sub.2SO.sub.4. The mixture is heated up to 200-230 C. Then, during continuous operation, glycerol is added over 90 min at a rate of 380 L/min. During the addition of glycerol, acrolein and water were distilled off at a constant rate of 390 l/min such has to keep the volume within the stirred tank reactor constant with 1 ml. During 90 min 35.1 ml were distilled. The distillate consisted of water and acrolein.

Example 2

Continuous Synthesis of Acrolein from Glycerol

(5) In a continuous stirred tank reactor are placed 28 g glycerol, 80 g KHSO.sub.4 and 16 g KHSO.sub.4. The mixture is heated up to 200-230 C. Then, during continuous operation, glycerol is added over 300 min at a rate of 1600 L/min. During the addition of glycerol, acrolein and water were distilled off at a constant rate of 1230 l/min. During 300 min 365 ml were distilled. The distillate consisted of water and acrolein.

Example 3

Continuous Generation of a Compound (1) with R.SUB.1.=tert. butyl and R.SUB.2.R.SUB.3.R.SUB.4.H

(6) In a set-up as depicted in FIG. 1 the indicated process flows of the indicated compositions are reacted to form compound (1). with R.sub.1=tert. butyl and R.sub.2R.sub.3R.sub.4H. in a crude yield (based on tert-butylacetate) of 82% and a purity (determined by 1H-NMR, pyridine as internal standard) of 86%, indicating a yield of pure product of 71%.