Ligand‐ and Additive‐Free CuCl₂‐Catalyzed para‐C−H Alkylation of Aniline Derivatives via Carbene Insertion

Abstract

Transition metal-catalyzed CÀ H insertion reaction is a straightforward strategy to realize the direct functionalization of electric-rich (hetero)arenes. The known methods generally require metal catalysts chelating with well-defined ligands and the use of additives; a simple and practical catalytic system is still needed. We herein report a ligandand additive-free, CuCl 2 -catalyzed highly selective para-CÀ H carbene insertion of aniline derivatives using α-aryl-α-diazo esters. A diverse array of 1,1-diarylacetates were obtained in high yields with excellent chemo-and regioselectivity.

Recent Progress on Copper-Catalyzed C–C Bond Formation via C(sp2)–H Insertions Using Diazo and Related Compounds

“…Very recently, Shi's group described a similar type of reaction involving N-protected tetrahydroquinoline 4 and aryl--diazoesters 2 in the presence of CuCl 2 as the catalyst without any additive or ligand (Scheme 4). 23 Gratifyingly, a wide range of -aryl--diazoesters having electron-donating or electron-withdrawing groups were compatible, providing the desired para-C(sp 2 )-H alkylated products 5a-c in good to excellent yields. Impressively, an unprotected tetrahydroquinoline also reacted to afford the corresponding N-alkylated and C(sp 2 )-H alkylated product 5f in a good yield.…”