# Organophotoredox-Catalyzed Stereoselective Synthesis of Bicyclo[3.2.0]heptanes via [2+2] Photocycloaddition

## TL;DR

Scientists developed a new method to create specific 3D-shaped molecules using light and catalysts, achieving high selectivity in the process.

## Contribution

A stereoselective synthesis of bicyclo[3.2.0]heptanes via anion radical [2+2] photocycloaddition using chiral auxiliaries.

## Key findings

- Enantioenriched bicyclo[3.2.0]heptanes were synthesized using chiral oxazolidinone auxiliaries.
- The reaction proceeds via a syn-closure pathway, forming cis-anti diastereoisomers as major products.
- DFT calculations supported the proposed reaction mechanism consistent with experimental data.

## Abstract

The stereoselective synthesis of bicyclo[3.2.0]heptanes via an anion radical [2+2] photocycloaddition of aryl bis-enone derivatives was investigated. By employing chiral oxazolidinone auxiliaries bound to aryl bis-enone substrates, enantioenriched, highly substituted bicyclo[3.2.0]heptanes have been synthesized. The reaction, mediated by Eosin Y and promoted by LiBr under visible light irradiation, has been studied both experimentally and computationally to elucidate the mechanism and stereoselective outcomes. The process proceeds via a syn-closure pathway, leading to the formation of the corresponding cis-anti diastereoisomers as major products isolated and characterized by X-ray analysis; DFT calculations provided useful insights and computational support which allow a plausible reaction mechanism to be proposed that agrees with the collected experimental data.