A Bifunctional Chiral Disulfide Catalyst for Highly Enantioselective Anti-Markovnikov Hydrophosphinylation

By the strategic integration of squaramide with amino acid derivatives, a type of modular H-bonding catalyst for the enantioselective hydrogen atom transfer (HAT) process was developed. With these disulfides, a photoinduced asymmetric anti-Markovnikov hydrophosphinylation was achieved, providing a series of chiral <i>β</i>-hydroxyphosphine oxides with reasonable to high enantioselectivity. Mechanism studies revealed the critical role of the H-bonding interactions between the squaramide scaffold and radical intermediates in governing the enantioselectivity and catalytic reactivity.