Silylcyclocarbonylation (SiCCa) of alkynylamines catalyzed by rhodium complexes

Attempted silylcarbocyclization (SiCaC) of 2-allyl-1-propargyltetrahydroisoquinoline with HSiMe₂Ph and carbon monoxide catalyzed by Rh(acac) (CO)₂ unexpectedly gives 8-exo-silylmethylene-4,5-benzo-9-indolizidinone, 8-allyl-8-silylmethyl-4,5-benzo-9-indolizidinone, and a hydrosilylation product. Possible mechanisms are proposed for the observed facile N-allyl cleavage and allyl transfer as well as the silylcyclocarbonylation (SiCCa) of the alkynylamine generated in situ. The SiCCa reactions of 1-propargyltetrahydroisoquinoline, (R)-2-(3-butynyl) pyrrolidine, (S)-2-[(R)-1-hydroxy-3-butynyl] pyrrolidine and (S)-2-[diethynyl-(hydroxy) methyl] pyrrolidine are further investigated. These reactions give the corresponding indolizidine or pyrrolizidine skeletons in one step. The scope and limitation of the SiCCa reaction and related reactions are discussed.