Design and Synthesis of Thiophene-Based C 2 -Symmetric Chiral Phosphoric Acids on a Decahydroquinoxaline scaffold for Stereoselective Transformations

Abstract

In this study, the design and the synthesis of a thiophene-based phosphoric acid based on a chiral decahydroquinoxaline scaffold derived from enantiopure trans-1,2-diaminocyclohexane was reported. This catalyst was then employed in stereoselective transformations such as the enantioselective Friedel-Crafts reaction of indoles with imines to afford 3-indolyl methanamines. High yields (up to 98%) and high enantioselectivities (up to 98% ee) were obtained. DFT calculations were performed to investigate the key transition states, providing mechanistic insight and confirming the origin and sense of the observed stereochemical outcome.