Photochemistry of conjugated poliynes

Abstract

Regio- and site-selectivity and product structure in the photocycloaddition of conjugated poliyes with various alkenes are dependent on the terminal groups, the number of triple bonds and the substrate alkenes. The reaction normally proceeds through cumulene-type triplet excited states. 1-Aryl-4-(pentamethyldisilanyl)buta-1,3-diynes add to methanol or acetone on irradiation through interesting silacyclopropene intermediates. Photohydration and photo-addition of 1-arylbuta-1,3-diynes to alcohols are also dependent on the other terminal group and the substituents on the aryl group.