Borrowing hydrogen and dehydrogenative/oxidative cyclization reactions catalyzed by a CCC-NHC pincer Re complex: An air stable catalyst for the synthesis of α-alkylated ketones and quinolines

[Display omitted] Successful catalytic activity of the CCC-NHC pincer Re(I) complex was achieved for the borrowing hydrogen coupling reaction between primary and secondary benzylic alcohols. An expansive scope of 17 aromatic and 2 aliphatic substrates were investigated and isolated yields from 40% to 91% were collected. The aliphatic substrates yielded complex aldol self-condensation by-products. The catalytic activity of the CCC-NHC pincer Re(I) complex was also evaluated for the formation of quinolines via the dehydrogenative/oxidative cyclization of 2-aminobenzyl alcohols with benzylic ketones or secondary benzylic alcohols. Isolated yields from 68% to 87% were obtained for 12 examples. All products and by-products were fully characterized by 1H &13C NMR and mass spectroscopies. Control studies such as dehydrogenative and hydrogen transfer reaction were carried out, and the results from these experiments supported a proposed mechanism of a borrowing hydrogen coupling reaction catalyzed by the CCC-NHC pincer Re(I) complex.