The effectiveness of chiral auxiliaries in inducing diastereoselectivity during photocyclization of ten differnt alpha-mesitylacetophenones to 2-indanols in crystalline state and as zeolite inclusion complexes has been examined. In the systems examined the chiral auxiliary functioned better within zeolites than in crystals. Crystal structure analysis of three alpha-mesitylacetophenones revealed that the low chiral induction in the crystalline state is either due to the presence of conformational isomerism in the reactant part of the molecule or the absence of communication between the chiral auxiliary and the reactant part of the ketone.