Viability of a Covalent Chiral Auxiliary Method to Induce Asymmetric Induction in Solid-State Photoreactions Explored

The effectiveness of covalent chiral auxiliaries in inducing stereoselectivity during the Yang type II photocyclization reaction was examined using the benzonorbornene phenyl ketone (2) and α-adamantylacetophenone (7) systems. The outstanding ability of covalent chiral auxiliaries in generating high asymmetric induction in the photoproducts has been established in 7 of the 10 investigated examples. Three examples in which molecules crystallize with equal amounts of conformational isomers in the asymmetric unit, despite the covalently linked chiral auxiliary, highlight the limits of the use of the covalent chiral auxiliary approach for asymmetric induction in the solid state.