1622-67-9

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The invention relates to an environmentally friendly preparation method for vitamin B6. The method comprises the following steps: carrying out a condensation reaction on a carbonyl compound and 2-cyano-2-cis-butene-1,4-diol which is used as a starting material, protecting hydroxyl groups to obtain 2,2-disubstituted-5-cyano-4,7-dihydro-1,3-dioxepine, carrying out a formylation reaction on the 2,2-disubstituted-5-cyano-4,7-dihydro-1,3-dioxepine, carbon monoxide and hydrogen to prepare 2,2-disubstituted-5-cyano-6-formyl-1,3-dioxetpin, condensing the 2,2-disubstituted-5-cyano-6-formyl-1,3-dioxetpin and 2-aminopropionate or its hydrochloride, and removing the carbonyl compound to prepare the vitamin B6. The method does not use a 4-methyl-5-alkoxyoxazole intermediate which is expensive and generates a large amount of wastewater in the production process, so the method has the advantages of environmentally friendly process, high reaction selectivity, high product purity, high atom economy, and suitableness for industrial production.

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 (I) and optionally for manufacturing pyridoxine involves performing an addition reaction between a 4-methyl-5-alkoxy-oxazole (II) and a 2-unsubstituted, 2-monosubstituted or 2,2-disubstituted 4,7-dihydro-(1,3)-dioxepin (III) in the substantial absence of a solvent and a catalyst to give a product mixture consisting essentially of the appropriate Diels-Alder adduct (IV) 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 (V) in a minor proportion, removal of a substantial proportion of the unreacted oxazole and dioxapin starting materials 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 IV to further V in the presence of said substantially anhydrous organic acid with removal of the generated alkanol by distillation under reduced pressure, and acylation of the resultingly enriched quantity of V with an added carboxylic acid anhydride to produce the desired I, and optionally converting this so-manufactured acylation product I to pyridoxine by acid hydrolysis for achieving deprotection and deacylatiom. Pyridoxine is a well known form of vitamin B6 with well established utility.

The invention relates to a method for producing pyridoxine and the acid addition salts thereof, said method comprising the following steps: i. the Diels-Alder adduct (I) of 4-methyloxazole and a 4,7-dihydro-1,3-dioxepin is dissolved in a mixture of an organic solvent which can be at least partially mixed with water, and water, and the solution of (I) thus obtained is treated at an elevated temperature, optionally in the presence of a catalytically active quantity of an acid, until at least part of the compound (I) is converted into the corresponding 1,5-dihydro-8-methyl-[1,3]dioxepin-[5,6c]pyridin-9-ol (II); ii. the compound (II) of the solution obtained in step i., or the acid addition salt of said compound, is precipitated by adding a precipitant, and the compound (II) or the acid addition salt thereof is isolated; and iii. the compound (II) obtained in step i., or the acid addition salt thereof, is converted into pyridoxine or an acid addition salt thereof.