Visible-Light-Mediated Macrocyclization for the Formation of Azetine-Based Dimers
Cody Ng, Scott L. Kim, Ilia Kevlishvili, Gianmarco Terrones, Emily R. Wearing, Heather J. Kulik, Corinna S. Schindler
Abstract
Macrocyclic dimeric lactones have pharmacological activities that make them attractive synthetic targets, but typical synthetic strategies employ an iterative approach to construct the macrocycle. Herein, we report a visible-light-mediated approach that enables facile access to 1- and 2-azetine-based dimeric lactones of up to 30-membered ring macrocycles. These products form via four consecutive triplet energy transfers for 1-azetine dimeric products and two consecutive triplet energy transfers for 2-azetine dimeric products. Computational investigations provide insights into the mechanism of this reaction, consistent with an unexpected initial intermolecular [2 + 2]-cycloaddition being preferred under nonstandard Curtin–Hammett conditions over the corresponding intramolecular reaction, which ultimately enables an efficient reaction pathway for macrocyclic dimerization.