Indium(III)-Catalyzed Reductive Bromination and Iodination of Carboxylic Acids to Alkyl Bromides and Iodides: Scope, Mechanism, and One-Pot Transformation to Alkyl Halides and Amine Derivatives

Highly effective indium(III)-catalyzed reductive bromination or iodination of a variety of carboxylic acids with 1,1,3,3-tetramethyldisiloxane (TMDS) and a source of bromine or iodine is described. This functional group interconversion has high tolerance for several functional groups, such as halogens, a hydroxy group, a nitro group, an olefin part, and a sulfide moiety. This indium catalytic system is also applicable to the reductive iodination of aldehyded, acyl chlorides, and esters. Furthermore, this reducing system can be applied to the one-pot synthesis of alkyl halides and amine derivatives via the addition of nucleophiles. Insight into the reaction mechanism was gained via the time course of H-1 and C-13 NMR monitoring experiments and the corresponding stepwise reactions.