Royal Society of Chemistry, Organic Chemistry Frontiers, 2(2), p. 150-158, 2015
DOI: 10.1039/c4qo00317a
Full text: Unavailable
The reduction of secondary amides to amines is an important transformation for the total synthesis of alkaloids and pharmaceuticals. General and chemoselective direct methods for this transformation are scarce. We report in this paper a simple method for the direct reduction of secondary amides, which uses only two reagents, triflic anhydride for amide activation, and NaBH4 for reduction. Running under mild conditions (0 C to rt), the reaction works well with several types of secondary amides including aromatic and aliphatic amides, α,β-unsaturated amide. The reaction displays good functional group tolerance for a series of reducible functional groups. The method is applicable to the direct reduction of C-H lithiation – functionalization products, and C-H activation – functionalization products. Moreover, chemoselective reduction of secondary lactams has been achieved using Cp2ZrHCl - NaBH4 combination.