名称:
Bis(2-acetoxyacrylonitrile) and its phenylene and alkylene bis homologs. Preparation, isomerization, and intramolecular [2 + 2] photocycloaddition
摘要:
The title compounds, 1,4-diacetoxy-1,4-dicyano-1,3-butadiene (3), 1,6-diacetoxy-1,6-dicyano-1,5-hexadiene (8), 1,2-bis(2-acetoxy-2-cyanovinyl)benzene (13), and 1,4-bis(2-acetoxy-2-cyanovinyl)benzene (17) were prepared by acetylation of the corresponding diacyl dicyanides. Dicyanides were prepared from diacyl chlorides by reaction with cyanotrimethylsilane or the NaI-Cu2(CN)2 reagent. Among the three geometrical isomers of the title compounds, the Z,Z diene predominated in 8 whereas E,E dienes predominated in conjugated dienes 3, 13, and 17. Conjugated E,E dienes underwent photoisomerization to E,Z and Z,Z isomers much faster than unconjugated diene 8. Prolonged irradiation on 13 yielded intramolecular [2 + 2] cycloadducts endo, exo- and exo,exo-5,6-diacetoxy-5,6-dicyano-2,3-benzobicyclo[2.1.1]hex-2-ene (22). Photochemistry in the formation of 22 is discussed.