B(C ₆ F ₅ ) ₃ -Catalyzed Exhaustive Reduction of Carboxylic Acids to Alkanes with Pinacolborane

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.