Strain-release photocatalytic access to rigidified isosteres of bicyclic heterocycles

We present the synthesis of fused isoxazolidine-pyrrolidine architectures via a dual rigidification strategy. These frameworks are accessed through an atom-economical approach using variously substituted isoxazolines and bicyclo[1.1.0]butane (BCB) derivatives under mild conditions. Subsequent functionalization of these analogs enables the synthesis of structurally diverse, disubstituted bridged pyrrolidines and proline derivatives that are otherwise challenging to access. This approach efficiently generates complex, rigid scaffolds, thereby expanding the chemical space available for the design of medicinally relevant small molecules.