Catalytic asymmetric transannulation of NH-1,2,3-triazoles with olefins

A convenient one-pot asymmetric synthesis of 2,3-dihydropyrroles from in situ generated triflated triazoles and olefins is described that further expands the utility of azavinyl carbene chemistry and provides access to an important class of cyclic enamides. Mechanistic investigations support the involvement of triflated cyclopropylaldimine intermediates in the formation of 2,3-dihydropyrrole. To the best of our knowledge, this is the first example of a chiral Brønsted acid catalyzed rearrangement of cyclopropylimines into enantioenriched 2,3-dihydropyrroles. Enantioenriched dihydropyrroles can be generated by a rhodium(II)-catalyzed asymmetric transannulation between sulfonyl-1,2,3-triazoles and electron-rich styrenes. Mechanistic investigations support the formation of cyclopropane intermediates which undergo ring expansion to 2,3-dihydropyrroles in the presence of a chiral Brønsted acid catalyst.