Allylation of Imines and Their Derivatives with Organoboron Reagents: Stereocontrolled Synthesis of Homoallylic Amines

Homoallylic amines serve as important precursors for the synthesis of a variety of natural products and pharmaceutically relevant compounds. One widely used strategy for homoallylic amine synthesis is the addition of allylic metal or metalloid derivatives to imines or related functional groups. The use of allylic boron compounds for these reactions has emerged as an important synthetic approach, providing a robust and chemoselective method for efficient and stereocontrolled access to various homoallylic amines. In this review, a comprehensive and critical analysis of imine allyl-boration and crotylboration methods using organoborane, organoboronate and potassium organotrifluoroborate reagents is provided. These approaches include direct methods that accomplish diastereo- or enantiocontrolled addition of the organoboron species. Additionally, organoboron-based transition-metal-catalyzed allylation of imines and their respective surrogates using copper, indium, iridium, palladium or zinc catalysis is discussed. Finally, coverage on the use of allenyl- and propargylboron compounds and their application for the synthesis of homopropargylic and homoallenyl amines is provided.