Photochemical phosphorus-enabled scaffold remodeling of carboxylic acids
Qiupeng Peng, Meemie U. Hwang, Ángel Rentería‐Gómez, Poulami Mukherjee, Ryan M. Young, Yunfan Qiu, Michael R. Wasielewski, Osvaldo Gutiérrez, Karl A. Scheidt
Abstract
The excitation of carbonyl compounds by light to generate radical intermediates has historically been restricted to ketones and aldehydes; carboxylic acids have been overlooked because of high energy requirements and low quantum efficiency. A successful activation strategy would necessitate a bathochromic shift in the absorbance profile, an increase in triplet diradical lifetime, and ease of further functionalization. We present a single-flask transformation of carboxylic acids to acyl phosphonates that can access synthetically useful triplet diradicals under visible light or near-ultraviolet irradiation. The use of phosphorus circumvents unproductive Norrish type I processes, promoting selectivity that enables hydrogen-atom transfer reactivity. Use of this strategy promotes the efficient scaffold remodeling of carboxylic acids through various annulation, contraction, and expansion manifolds.