Preparation of acrylic acid derivatives from α- or β-hydroxy carboxylic acids
The invention is directed to a process for the preparation of α,β-unsaturated acids, esters and amides from α- or β-hydroxycarboxylic acids or esters or precursors in high yields and high selectivity. The α,β-unsaturated acids or esters are optionally prepared in the presence of specific dehydration and/or esterification catalysts. The α,β-unsaturated amides or substituted amides are prepared optionally in the presence of a dehydration and/or amidation catalyst. The source of α- or β-hydroxycarboxylic acids or precusor is preferably from a renewable resource. The precursor is defined herein.
1. A process for preparing an α, β-unsaturated amide, α,β-unsaturated N-substituted amide or α,β-unsaturated N,N-disubstituted amide of formula (I)
wherein R 1 , and R 2 are independently H, C 1 -C 6 alkyl, cycloalkyl, or R 1 and R 2 can form a ring, wherein the ring is selected from the group consisting of morpholine, piperazine, piperidine and pyrrolidine, R 3 is H or C 1 -C 4 alkyl and R 4 is H, methyl or ehtyl which process comprises the steps of
a) forming an aqueous solution comprising at least one of
an α- or β-hydroxycarboxylic acid;
an α- or β-hydroxycarboxylic salt;
an α- or β-hydroxycarboxylic ester;
or
cyclic lactide, 3,6-dimethyl-1, 4-dioxane-2, 5-dione
and
b) heating the aqueous solution of step a) in the presence of an amine or an amine salt of the α- or β-hydroxycarboxylic acid, wherein amidation and dehydration occurs
optionally in the presence of a dehydration and/or amidation catalyst.
2. A process according to claim 1 , wherein the aqueous solution is exposed to a heated surface to vaporize the solution to form the α,β-unsaturated amide, α,β-unsaturated N-substituted amide or α,β-unsaturated N, N-disubstituted amide.
3. A process according to claim 1 , wherein the formation of the α,β-unsaturated amide, α,β-unsaturated N-substituted amide or the α,β-unsaturated N, N-disubstituted amide is in the liquid phase.
4. A process according to claim 1 , wherein the amine and at least one of
an α- or β-hydroxycarboxylic acid;
an α- or β-hydroxycarboxylic salt;
an α- or β-hydroxycarboxylic ester;
or cyclic lactide, 3,6-dimethyl-1, 4-dioaxne-2, 5-dione
are fed into a reaction vessel or a vapor phase reactor separately.
5. A process according to claim 1 , wherein the process is continuous, batch or fed-batch.
6. A process according to claim 1 , wherein the α- or β-hydroxycarboxylic acid, the α- or β-hydroxycarboxylic salt or α- or β-hydroxycarboxylic ester thereof is selected from the group consisting of lactic acid, 3-hydroxypropionic acid, 3-hydroxybutyric acid and 3- or 2-hydroxyisobutyric acid, salts or esters thereof.
7. A process according to claim 1 , wherein the compound of formula (I) is selected from the group consisting of (meth)acrylamide, N-methyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-ethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-morpholino (meth)acrylamide and N-methyl-N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide and N-tert-butyl (meth)acrylamide.
8. A process for preparation of α,β-unsaturated amides, α,β-unsaturated N-substituted amides or N,N-disubstituted amides comprising
a) forming an aqueous solution comprising an α- or β-hydroxycarboxylic acid, α- or β-hydroxycarboxylic esters or α- or β-hydroxycarboxylic acid salts,
b) cyclizing to form a cyclic lactide, and
c) heating the formed polyester or lactide of step b) in the presence of an amine, wherein amidation and dehydration occurs optionally in the presence of a dehydration and/or amidation catalyst.
9. A process according to claim 8 , wherein the α- or β-hydroxycarboxylic acid is lactic acid, 2-hydroxyisobutyric acid, 3-hydroxypropanoic acid, 3-hydroxybutyric acid and 3- or 2-hydroxyisobutyric acid, salts or esters thereof.
10. A process according to claim 8 , wherein the cyclic lactide is 3,6-dimethyl-1, 4-dioxane-2,5-dione.
11. A process according to claim 8 , wherein the aqueous solution is exposed to a heated surface to vaporize the lactide and amine to form the α,β-unsaturated amide or α,β-unsaturated N-substituted or α,β-unsaturated N,N-disubstituted amide.
12. A process according to claim 8 , wherein the amidation and dehydration ocurs in a vapor phase.
13. A process according to claim 1 , wherein step b) further comprises a polymerization inhibitor.
14. A process according to claim 1 , wherein the amidation and dehydration occurs in a vapor phase.
15. A process according to claim 1 , wherein the aqueous solution of step a) contains an amine salt of the α-or β-hydroxycarboxylic acid.
16. A process according to claim 15 , wherein amidation and dehydration occurs in a vapor phase.