Abstract
New synthesis of 2,4-diacetylpyridine 1 was achieved by Claisen condensation of 2,4-diethoxycarbonylpyridine 2a with ethyl acetate. Reduction of 1 with zinc or its salt in hydrochloric, formic or acetic acids afforded mixtures of ketocarbinol 4, dicarbinol 5 or diethyl pyridine 6 derivatives. Formation of 6 as the complete reduction product was chemically proved to proceed via 4 and 5. Electrochemical(1) reduction of 2a gave 2,4-dimethylpyridine 7 and that of 1 gave rise to a mixture of 5 and 6 along with 2,4-diethyl-1,2,5,6-tetrahydropyridine 8 and 2,4-diethylpiperidine 9. Finally, metal hydride reduction of 1 gave 5, and that of diesters 2 or diacid chloride 10 derivatives afforded 2,4-dihydroxymethylpyridine 11.