Reactivities of 3‐ and 4‐halogenopyridines towards potassium tert‐butoxide and potassium benzenethiolate (thiophenoxide) in dimethyl sulfoxide

Abstract

When 3‐ and 4‐fluoropyridine are treated with a mixture of potassium tert‐butoxide and potassium benzenethiolate (thiophenoxide) in dimethyl sulfoxide (DMSO), they are converted into the corresponding tert‐butoxypyridines by an addition‐elimination mechanism. The 3‐ and 4‐bromo‐and‐iodo‐pyridines react mainly by the EA‐mechanism via 3,4‐didehydropyridine producing mixtures of principally 3‐ and 4‐(phenylthio)pyridine and partly according to the AE‐mechanism with potassium benzenethiolate.Reactivities of the halogenopyridines towards potassium tert‐butoxide and potassium benzenethiolate are compared with those towards other bases. The formation of 3,4‐didehydropyridine as an intermediate in the reactions of 3‐bromopyridine with both potassium tert‐butoxide and potassium amide was confirmed by trapping it with furan.