CROWN-ETHER STYRYL DYES .15. SYNTHESIS AND 2 PATHWAYS OF REGIOSPECIFIC AND STEREOSPECIFIC CATION-DEPENDENT [2-AUTOPHOTOCYCLOADDITION OF CHROMOGENIC 15-CROWN-5-ETHER BETAINES OF QUINOLINE SERIES(2])

Styryl dyes (4a,b) containing a 15-crown-5 fragment and isomeric 2- an d 4-quinolinium residues with an N-sulfopropyl substituent undergo [22] -autophotocycloaddition to give cyclobutane derivatives (9a,b) in a cetonitrile only in the presence of Mg(ClO4)(2) or Ca(ClO4)(2). The st ereospecificity of both pathways of photocycloaddition and its efficie ncy are explained by the preorganization of the supramolecular dimers derived from the trans-isomers of the dyes when they are bound into co mplexes with Mg and Ca cations.