Stoichiometry Dependence\nin the Consecutive, Competing\nReduction, Halogenation, or Deoxygenation of Aryl Carbonyls

Six\nfundamental chemical transformations of aryl carbonyls are\nachieved by properly adjusting the stoichiometry of the borane-amine\nand titanium tetrachloride reagent system. This set of reagents acts\ncollectively as a hydride donor, Lewis acid catalyst, and halogen\nsource for the reduction of carbonyls to alcohols, reductive halogenation\nof carbonyls to halides, deoxygenation of carbonyls to alkanes, dehydroxyhalogenation\nof alcohols to halides, deoxygenation of alcohols to alkanes, and\nhydrodehalogenation of halides to alkanes. While the carbonyl reduction\nis broadly applicable to both aromatic and aliphatic substrates, the\nremaining reactions are dependent on the stability of the proposed\ncarbocationic intermediates, enabling highly selective reactions at\nthe substrates’ benzylic position. This unique selectivity\nallows benzylic dehalogenation in the presence of aryl and alkyl halides\nin addition to highly selective dehydroxyhalogenation of alcohols\neven for tertiary versus secondary aliphatic and secondary versus\nprimary benzylic substrates using only titanium tetrachloride as the\nchlorinating agent.