Palladium‐Catalyzed Cascade C−H Functionalization/Asymmetric Allylation Reaction of Aryl α‐Diazoamides and Allenes: Lewis Acid Makes a Difference

Abstract

A Pd‐catalyzed cascade C−H functionalization/asymmetric allylation reaction with aryl α‐diazoamides and allenes has been developed. The reaction provides an efficient approach to construct chiral 3,3‐disubstituted oxindole derivatives in high levels of yield and enantioselectivity (up to 93 % ee). Notably, the chromium complex works as Lewis acid to facilitate the formation of palladium carbene and to enhance acidity of carboxylic acid, allowing for higher stereochemical control and efficiency.

Recent advances in Pd-catalyzed asymmetric cyclization reactions

“…Recently, a palladium-catalyzed cascade C–H functionalization/asymmetric allylation reaction of aryl α-diazoamides 561 and allenes 560 enabled by a standard Trost ligand to construct chiral 3,3-disubstituted oxindole derivatives 562 with high performance was demonstrated by Gong, Han and co-workers (Scheme 132). 253 The putative mechanism involved the hydropalladation of allene with a Pd–H species generated from Pd(0) and acid, leading to the formation of a π-allyl Pd( ii ) complex, which could lead to the decomposition of the diazo compound to yield the palladium carbene intermediate Int-I . The following intramolecular C(sp 2 )–H insertion led to the production of intermediate Int-II and subsequent asymmetric allylation reaction led to the formation of allylic 3,3-disubstituted oxindole products.…”