Cyclodextrin mediated enantio and diastereoselective geometric photoisomerization of diphenylcyclopropane and its derivatives

cis-Diphenylcyclopropanes upon direct excitation and triplet sensitization undergo geometric isomerization to the corresponding trans isomers. In solution the trans isomers are formed as a 1:1 enantiomeric or diasteromeric mixture. Upon inclusion within β-cyclodextrin the same molecules give the trans isomers enriched in one optical isomer. Enantiomeric excess and diasteromeric excess induced by the optically active host β-cyclodextrin although small is mechanistically significant.