Topochemical Photopolymerization of 4-cinnamates and -thiocinnamates in the Crystalline State

Article abstract of DOI:10.1246/bcsj.68.2355

Topochemical photopolymerization of 4-<2-(unsubstituted and methyl-substituted pyrazinyl)ethenyl>-cinnamates and -thiocinnamates were carried out in the crystalline state.Upon photoirradiation, ethyl 4-<2-(unsubstituted and methyl-substituted pyrazinyl)ethenyl>cinnamates and S-ethyl 4-<2-(unsubstituted and methyl-substituted pyrazinyl)ethenyl>thiocynnamates gave α-hetero-type crystallinem linear polymers, whereas methyl 4-<2-(methyl-substituted pyrazinyl)ethenyl>cinnamates afforded mixtures of β-type oligomers.The X-ray crystallographic analyses of the monomers revealed that the thioesters were more favorable monomers that the corresponding esters from the viewpoint of close packing in a crystal.The following factor(s) would play an important role in determining their molecular arrangements: 1) The close contact between the central 1,4-phenylene ring and the alkoxy oxygen of the ester group or the alkylthio sulfur of the thioester group, 2) the hydrogen bond between the interstacked pyrazinyl groups, and/or 3) the gearing of the alkyl group in the ester moiety with the methylpyrazinyl group.