Direct and efficient synthesis of tetrasubstituted allenyl organothiophosphates from propargylic alcohols under catalyst- and additive-free conditions

Abstract

An environment-friendly approach that affords tetrasubstituted allenyl organothiophosphates containing highly congested carbon centers from easily prepared propargylic alcohols and phosphorothioic acids [(RO)₂P(O)SH] with water as the only by-product is developed. The reaction is carried out by an in situ dehydrative cross-coupling process involving the allenyl carbocation intermediate and followed by nucleophilic attack to achieve high product distribution. In addition, the reaction occurred in the presence of (EtO)₂P(O)SH, and no ligand, additive or additional acid promoter was needed. It is noted that (EtO)₂P(O)SH acts not only as an acid promoter but also as a nucleophile. Moreover, a variety of propargylic alcohols bearing electron-rich and electron-withdrawing groups were well tolerated to generate various tetrasubstituted allenyl organothiophosphates in moderate to excellent yields under mild conditions.