Patent ID: 7495101
Filing Date: 2009-02-24
Classification: C07D,Y02P

Abstract:
1. A process for manufacturing a 3-unsubstituted, 3-monosubstituted or 3,3-disubstituted 9-acyloxy-1-5-dihydro-8-methylpyrido [3,4-e] [1,3]dioxepin of general formula wherein each of R and optionally for manufacturing pyridoxine, wherein the process comprises performing addition reaction between a 4-methyl-5-alkoxy-oxazole of the general formula wherein R and a 2-unsubstituted, 2-monosubstituted or 2,2-disubstituted 4,7-dihydro-(1,3)-dioxepin of the general formula wherein R in the substantial absence of a solvent and a catalyst to give a product mixture consisting essentially of the appropriate Diels-Alder adduct of the general formula wherein R in a major proportion and the appropriate 3-unsubstituted, 3-monosubstituted or 3,3-disubstituted 1,5-dihydro-8-methylpyrido[3,4-e] [1,3]dioxepin-9-ol of the general formula wherein R in a minor proportion, removal of a substantial proportion of the unreacted starting materials of formulae II and III from the product mixture by distillation under reduced pressure, addition of a substantially anhydrous organic acid to said product mixture and rearrangement of the Diels-Alder adduct of the formula IV present therein to further 3-unsubstituted, 3-monosubstituted or 3,3-disubstituted 1,5-dihydro-8-methylpyrido[3,4-e] [1,3]dioxepin-9-ol of the formula V in the presence of said substantially anhydrous organic acid with removal of the generated alkanol R acylation of the resultingly enriched quantity of the methylpyrido[3,4-e] [1,3]dioxepin-9-ol of the formula V with an added carboxylic acid anhydride of the general formula wherein R to produce the desired 3-unsubstituted, 3-monosubstituted or 3,3-disubstituted 9-acyloxy-1,5-dihydro-8-methylpyrido[3,4-e] [1,3]dioxepin of the formula I, and optionally converting this so-manufactured acylation product of the formula I to pyridoxine by acid hydrolysis for achieving deprotection and deacylation.