Highly diastereoselective photochromic ring closure of bisbenzothienylethenes possessing dual fluorinated stereocontrollers

Three regioisomeric bisbenzothienylethenes equipped with two (R)-pentafluoropropanoyloxyethyl groups on both ends of the hexatriene moiety displayed high diastereoselectivity towards light-induced 6π-electrocyclization reactions, particularly in polar solvents. In non-polar solvents such as hexane and octafluorotoluene, however, diastereoselectivity was not very high owing to the fluorophobic or less fluorophilic interactions, respectively, between the fluoroalkanoyl side chains and the solvent molecules.