Selective Phosphoranation of Unactivated Alkynes with Phosphonium Cation To Achieve Isoquinoline Synthesis

We
herein develop a selective phosphoranation of alkynes with phosphonium
cation, which directs a concise approach to isoquinolines from unactivated
alkyne and nitrile feedstocks in a single step. Mechanistic studies
suggest that the annulation reaction is initiated by the unprecedented
phosphoranation of alkynes, thus representing a unique reaction pattern
of phosphonium salts and distinguishing it from existing protocols
that largely rely on the utilization of highly functionalized imines/oximes
and/or highly polarized alkynes.