This study introduces a novel method for the complete reduction of carboxylic acids to methylarenes, employing pinacolborane as the reductant catalyzed by B(C6F5)3. The present protocol proves compatible with various sensitive functionalities, notably hydroxy, carbonyl, vinyl, and ester groups. Furthermore, its synthetic utility is highlighted by the successful gram-scale, late-stage functionalization of the dermatological drug adapalene. Mechanistic studies support a proposed pathway involving sequential hydroboration and deboration steps.
Shao et al. (Fri,) studied this question.