Simple and selective one-pot replacement of the N-methyl group of tertiaryamines by quaternization and demethylation with sodium sulfide or potassium thioacetate: an application to the synthesis of pergolide

The paper describes a mild, selective, and rapid replacement of an N-methyl group of tertiary amines with other alkyl groups via a simple one-pot proc edure. This transformation is easily achieved by preparation of the appropr iate quaternary ammonium salt in sulfolane and in situ treatment with sodiu m sulfide or potassium thioacetate. The protocol is successfully applied to the transformation of dihydrolysergol, dextromethorphan and laudanosine (a s models of ergot and opium N-methyl alkaloids) into various A-alkyl congen ers.