Crown ether styryl dyes 24.* Synthesis of multiphotochromic 15-crown-5 ethers with rigid spacers, their anion-"capped" complexes, and stereospecific [2+2] autophotocycloaddition

Article abstract of DOI:10.1007/BF02495515

Novel styryl dyes (trans-2a,b) containing a 15-crown-5 ether moiety and an N-sulfobenzyl spacer were synthesized. The reactions of trans-2a,b with Mg(ClO₄)₂ in MeCN afford dimeric complexes. During photolysis of the latter, trans-cis isomerization to give anion-"capped" complexes (cis-2a,b)·Mg²⁺ and stereospecific [2+2] autocycloaddition to yield cyclobutane derivative occur in parallel. The ratio of the two transformation pathways of dyes 2a,b depends on the spacer type. To interpret the experimental data, the molecular-mechanics and semiempirical quantum-chemical calculations were performed.