Asymmetric Synthesis of 3-Pyrrolines through an Aryne-Induced Domino Process

Abstract

Production of chiral compounds by green processes like domino reactions is of importance to environmental protection and sustainable development. Nevertheless, finding an appropriate catalyst to control enantioselectivity with satisfaction is a major challenge. Here, we report the accomplishment of a newly developed domino reaction for synthesizing optically active 3-pyrrolines, a class of compounds with various biological properties. The reaction involves the use of (trimethylsilyl)aryl triflates, Schiff bases, and alkynes in the presence of a chiral catalyst (R)-(−)-1,1′-binaphthyl-2,2′-diyl hydrogenphosphate. The key features of this new reaction include the generation of a single product in very good yields (75–85%) with high stereo- and enantio-selectivity; the enantiomeric ratio reaches as high as 98.5 : 1.5. Moreover, it involves an aryne-induced domino reaction and an unusual 1,4-intramolecular proton transfer, which overwhelms the well-established 1,5-proton transfer.