Intramolecular [2+2] Cycloaddition of N‐Allylcinnamamines and <i>N</i>‐Allylcinnamamides by Visible‐Light Photocatalysis

Abstract

The visible light‐promoted intramolecular [2+2] cycloaddition of N ‐allylcinnamamines and N ‐allylcinnamamides in the presence of catalytic amounts of [Ir{dF(CF 3 )ppy} 2 (dtbpy)]PF 6 is reported. Low energy visible light and a high triplet energy iridium‐photosensitizer were efficient at promoting the cycloaddition reaction of N ‐allylcinnamamides and N ‐allylcinnamamines to the corresponding aryl‐3‐azabicyclo[3.2.0]heptanones and aryl‐3‐azabicyclo[3.2.0]heptanes, respectively, with high diastereoselectivity and under mild conditions. Azabicyclic fused rings have been employed as surrogates for piperidine motifs in drug discovery. Functional groups useful for deployment and/or elaboration in drug discovery campaigns were all shown to be tolerated, including halides, CF 3 , cyanide, ester, acetamide, acetate, CH 3 O, pyridyl, furan, carbamate, tosyl, benzyl, and benzoate.