Dual Supramolecular Photochirogenesis: Ultimate Stereocontrol of Photocyclodimerization by a Chiral Scaffold and Confining Host

In contrast to the brilliant success in thermal asymmetric synthesis, precise stereocontrol remains a great challenge in chiral photochemistry because of the lack of effective tools and methodologies for controlling the short-lived, weakly interacting, and highly reactive electronically excited species. In this work, we achieved this goal through the "dual-chiral, dual-supramolecular" photochirogenesis approach, which enabled us to realized dramatic acceleration and perfect stereocontrol in one of the most representative photoreactions. Thus, the [4 + 4] photocyclodimerization of 2-anthracenecarboxylate tethered to an a-cyclodextrin scaffold was accelerated by a gamma-cyclodextrin or cucurbit[8]uril host and gave a single enantiomeric cyclodimer (out of four possible chiral and achiral stereo-isomers) in up to 98% chemical and 99% optical yield.