Catalyst-Controlled Divergent Strain-Release Amination and Skeletal Remodeling of Bicyclo[1.1.0]Butanes

Catalyst-controlled nitrene transfer enables divergent amination reactions of bicyclo[1.1.0]butanes through distinct modes of activation of their highly strained central σ-bond. Under Rh(II) catalysis, bicyclo[1.1.0]butanes undergo selective strain-release amination to furnish aminocyclobutenes, which provide efficient access to cyclobutane amino acids through a simple amination-hydrogenation sequence. In contrast, photocatalytic nitrene activation redirects the reaction pathway toward double amination and skeletal remodeling, affording functionalized dihydropyrrolidines that can be readily converted into pyrrole heterocycles under acidic conditions. The synthetic utility of both approaches is further demonstrated, for example, in a telescoped synthesis of cyclobutane amino acids from diazo precursors or downstream diversification reactions. Mechanistic experiments and computational studies reveal distinct catalyst-dependent nitrene activation pathways that govern the fate of a common reactive intermediate and underpin the observed divergent reactivity.