Transition metal-catalyzed synthesis of cyclopropenes and N-fused heterocycles.

摘要

A novel highly efficient direct palladium-catalyzed arylation of cyclopropenes has been developed. This protocol provides convenient access to a wide array of tetrasubstituted cyclopropenes. It has been shown that this methodology is applicable to the synthesis of valuable optically active tetrasubstituted cyclopropenes, which are not available via asymmetric cyclopropenation methods. Mechanistic data strongly support electrophilic pathway for this transformation.;It has been demonstrated that N-fused 1,2,3-triazoles may serve as direct and convenient precursors for the Rh-carbenoids. An efficient approach towards previously unavailable 3-iminocyclopropenes via the Rh(II)-catalyzed cyclopropenation of triazoles with terminal alkynes has been developed. It has been shown that 3-iminocyclopropenes undergo facile and regiodivergent transition metal-catalyzed cycloisomerization into N-fused heterocycles. The high regioselectivity is effectively controlled by metal catalyst, which allows for efficient synthesis of 1,3- and 1,2-substituted N-fused pyrroles, including pyrrolooxazole, pyrroloisoquinoline and indolizines.;A highly efficient synthetic approach towards N-fused pyrroles and imidazoles has been developed. It has been shown that readily available and easy to handle N-fused 1,2,3-triazoles smoothly undergo a novel Rh(II)-catalyzed transannulation with various nitriles and terminal alkynes to produce imidazo[1,5-a]pyridines and indolizines, respectively. The obtained experimental data suggest Rh-carbenoid-mediated ylide-type mechanism for this annulation reaction.