Reductive Amination of Biomass-Based Levulinic Acid into Pyrrolidone by Protic Ionic Liquid via Dehydrogenation of Dimethyl Amine Borane

One-Pot, Tandem Reductive Amination/Alkylation–Cycloamidation for Lactam Synthesis from Keto or Amino Acids

“…This pathway involving one-pot, repetitive N–C bond formations relies heavily on the chemoselectivity of the reagent. Several transition metal catalysts, mostly precious metals, in combination with a reducing agent have been examined for such transformations (Scheme A). − For catalyst-free protocols, formic acid and hydrosilanes have been explored as mild and highly selective reducing agents for achieving similar targets, although siloxane is an unavoidable effluent of the hydrosilane protocols (Scheme B). , Recently, borane-amines have been explored for tandem reductive amination–amidation, though the reported protocols are limited to the use of levulinic acid or have poor yields with other substrates. , …”

“…18,19 Recently, borane-amines have been explored for tandem reductive amination−amidation, though the reported protocols are limited to the use of levulinic acid or have poor yields with other substrates. 20,21 As part of our program exploring the chemistry of boraneamines, we have recently reported on the reductive amination of carbonyls 22 as well as their versatility for direct amidation of carboxylic acids. 23,24 Fine-tuning borane-amines by decreasing their reducing strength via conversion to monotrifluoroacetoxyborane-amines [TFAB-amines (1)], such as TFAB-NH 3 (1a) and TFAB-NEt 3 (1b), accomplished facile reductive amination even for challenging substrates.…”