Asymmetric catalysis relies on subtle interactions that bias a reaction toward one product at the expense of its mirror image. Strassfeld et al. studied the particular influences at play in a squaramide-catalyzed ring opening of oxetanes (C–C–C–O cycles). They found that two different mechanisms were operating simultaneously, respectively co-catalyzed by Lewis and Brønsted acids. The optimal catalyst induced high selectivity in both of them, attributable through modeling to favorable cation-pi and hydrogen-bonding interactions. Results such as these can shed light more generally on the nature of privileged catalyst motifs that prove selective in multiple distinct reaction scenarios.
J. Am. Chem. Soc. 143, 9585 (2021).