Enantioselective Synthesis of Azoniahelicenes by Rh-Catalyzed C–H Annulation with Alkynes

A rhodium­(III)-catalyzed enantio­selective
C–H activation/annulation
process is disclosed. With a catalyst derived from a chiral CpRh­(III)
complex and a chiral acid, the direct annulation reactions between
1-aryl isoquinoline derivatives and alkynes take place smoothly to
afford a series of chiral azonia­helicenes in excellent yields
and enantio­selectivity (up to 99% yield and 96% ee). Mechanistic
studies suggest that C–H bond cleavage may be the turnover-limiting
step.