Chemoselective cyclization of N-sulfonyl ketimines with ethenesulfonyl fluorides: access to trans-cyclopropanes and fused-dihydropyrroles

An interesting stereo-and chemoselective cyclization reaction of several N-sulfonyl ketimines as C/N-donors with a variety of alpha,beta-unsaturated sulfonyl fluorides promoted by DBU is reported. This substrate-dependent selective C-C vs. C-N bond cyclization process leads to important classes of transcyclopropane and fused dihydropyrrole scaffolds in satisfactory yields with excellent diastereoselectivities (dr up to <= 99: 1). High-yield single-stage synthesis of biologically interesting sulfamate-fused-pyrrole and 2-pyrrolyl phenol derivatives was successfully established.