Substrate-Regulated Divergent Addition of N-Sulfonyl Ketimines to Bicyclo[1.1.0]butanes Enabled by Photoinduced Energy Transfer

A substrate-regulated divergent addition of N-sulfonyl ketimines to bicyclo[1.1.0]butanes (BCBs) was developed using a photoinduced energy transfer strategy. The [2π+2σ] cycloaddition of BCBs with saccharin-derived cyclic ketimines yields benzosultam-fused aza-BCHs with good yields and excellent diastereoselectivity. In contrast, reactions of chain N-sulfonyl ketimines with BCBs produce 1,3-fully substituted cyclobutanes via energy-transfer-induced N-S bond homolysis. The ease of large-scale synthesis and derivatizations of products highlight their application potentials.