Visible-light-induced organocatalytic enantioselective N-H insertion of α-diazoesters enabled by indirect free carbene capture

While asymmetric insertion of metal carbenes into H-X (X = C, N, O, etc.) bonds has been well-established, asymmetric control over free carbenes is challenging due to the presence of strong background reactions and lack of any anchor for a catalyst interaction. Here we have achieved the first photo-induced metal-free asymmetric H-X bond insertion of this type. With visible light used as a promoter and a chiral phosphoric acid used as a catalyst, alpha-diazoesters and aryl amines underwent smooth N-H bond insertion to form enantioenriched alpha-aminoesters with high efficiency and good enantioselectivity under mild conditions. Key to the success was the use of DMSO as an additive, which served to rapidly capture the highly reactive free carbene intermediate to form a domesticated sulfoxonium ylide.

Automated summary

In this study, the first metal-free asymmetric H-X bond insertion of its kind was achieved by utilizing visible light as a promoter and a chiral phosphoric acid as a catalyst. Under mild conditions, alpha-diazoesters and aryl amines smoothly underwent N-H bond insertion to form enantioenriched alpha-aminoesters with high efficiency and good enantioselectivity. The key to success was the use of DMSO as an additive, which facilitated the rapid capture of the highly reactive free carbene intermediate to form a domesticated sulfoxonium ylide.