Intermediates and process for preparing pyridoxine and related compounds

2-Methyl-3-hydroxy-4,5-disubstituted pyridines are prepared by heating fumaric or maleic acid or a functional derivative thereof with 4-methyl-oxazole; a dehydrogenation agent is either present during the heating or is added later. Specified functional derivatives are esters, nitriles, acid halides, anhydrides, amides and N-substituted amides. Suitable dehydrogenation agents include nitrobenzene, halogenated and/or alkylated nitrobenzenes, halogenated ketones, salts such as mercuric acetate, palladium/charcoal in pseudocumene, bromine and quinones, e.g. chloranil; hexachloroacetone may be used in the presence of an acid such as acetic or propionic or methanol, dioxane, triethylamine or N,N-dimethylformamide. Temperatures up to 150 DEG C. may be used. Examples describe the preparation of 2-methyl-3-hydroxy-4,5-di (methoxycarbonyl-, ethoxycarbonyl- and cyano) pyridines; 2-methyl-3-hydroxy-5-cyanopyridine and 2-methyl-4, 5-dicyano-pyridine are obtained as by-products in the latter case. 4-methyloxazole starting material is prepared by treating ethyl acetoacetate with sulphuryl chloride to give ethyl-a -chloroacetoacetate, reacting this with formic acid and formamide to give 4-methyl-5-ethoxycarbonyloxazole which is hydrolysed with alkali to 4-methyl-5-carboxy-oxazole which is then decarboxylated with copper powder. The 2-methyl - 3 - hydroxy-4, 5-disubstituted pyridines may be converted to Vitamin B6. Thus, 4,5-diesters may be reduced with lithium aluminium hydride, and the 4,5-dicyano-compound may be hydrolysed and esterified and then reduced with lithium aluminium hydride or may be reduced to the bis (aminomethyl) compound and this converted to the vitamin by diazotisation in aqueous medium.