Sc(OTf)₃‐Catalyzed Bicyclization of o‐Alkynylanilines with Aldehydes: Ring‐Fused 1,2‐Dihydroquinolines

Abstract

A Sc(OTf) 3 -catalyzed cascade Prins-type cyclization reaction of o-alkynylanilines, bearing a hydroxy or amine functionality, with aldehydes affords 1,2-dihydroquinoline derivatives having an extra fused ring efficiently under mild reaction conditions. It is interesting to observe the reversed reactivity in the highly selective formation of 1,2-dihydroquinoline derivatives instead of the formation of the usually favored indole derivatives.

Alkynyl Halo-Aza-Prins Annulative Couplings

“…N -Sulfonyl iminium ions are the last class of electrophiles that have been employed in alkynyl aza-Prins chemistry. In these cyclizations, sulfonamide reactants are leveraged for the preparation of functionalized pyrazoles, indoles, indolines, and piperidines. , Recently, a report by Hou et al shows the use of bromotrimethylsilane (TMSBr) to promote the reaction of a sulfonamide 8 and a carbonyl coupling partner 9 to make tosyl-piperidines like 11 via N -tosyl iminium intermediate 10 (Scheme C).…”