Electron and hydrogen transfer reductions of some 2,4-disubstituted pyridines

New synthesis of 2,4-diacetylpyridine 1 was achieved by Claisen condensatio n of 2,4-diethoxycarbonylpyridine 2a with ethyl acetate. Reduction of 1 wit h zinc or its salt in hydrochloric, formic or acetic acids afforded mixture s of ketocarbinol 4, dicarbinol 5 or diethyl pyridine 6 derivatives. Format ion 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 hydr ide reduction of 1 gave 5, and that of diesters 2 or diacid chloride 10 der ivatives afforded 2,4-dihydroxymethylpyridine 11.