Unlocking Chromium Decarboxylative Ligand-to-Metal Charge Transfer: Efficient and Redox-Neutral Allylation of Aldehydes Using Carboxylic Acids

Here, we report the light-induced decarboxylative ligand-to-metal charge transfer (LMCT) of Cr(III) carboxylate complexes and demonstrate its applicability toward stereoselective Nozaki-Hiyama-Kishi (NHK) allylation reactions. The critical design element of our reaction was identifying a bipyridyl ligand scaffold that enables a single Cr catalyst to facilitate both photolytic dissociation and aldehyde addition. This approach allows for the direct utilization of carboxylic acids and eliminates the need for external redox reagents. The broad utility of this protocol was demonstrated by the preparation of a variety of homoallylic alcohols in good yields and diastereoselectivities as well as the identification of advantageous retrosynthetic disconnections. Extensive studies supported the LMCT mechanism of this transformation, including the characterization of the catalytically active Cr-carboxylate species.