Stereoselective Intermolecular [2 + 2] Cycloadditions of Erlenmeyer-Plöchl Azlactones Using Visible Light Photoredox Catalysis.

The first report of the preparation of symmetric and nonsymmetric diaminotruxinic derivatives through the photoredox [2 + 2] cycloadditions of Erlenmeyer azlactones is described, affording the desired compounds in high regio- and diastereocontrol (only head-to-head coupling). Mechanistic studies by DFT suggest that the reaction proceeds through a neutral photocatalytic pathway.