N-Heterocyclic carbene catalyzed asymmetric [3 + 3] cycloaddtion of β,β-disubstituted, α,β-unsaturated carboxylic esters with 3-aminobenzofurans

An N-heterocyclic carbene (NHC) catalyzed formal [3 + 3] cycloaddition reaction of β,β-disubstituted, α,β-unsaturated carboxylic esters with 3-aminobenzofurans is doucumented, furnishing benzofuran fused δ-lactams bearing an all-carbon quaternary stereocenter with moderate to excellent yields and excellent enantioselectivies. Further gram-scale preparation and synthetic transformation of the cycloadducts demonstrate good practicality and applicability of this β-carbon functionalization reaction.