Photochemical reactions. 143rd communication. Photochemistry of 5,6-epoxy-1,3-dienes in the ionone series. Influence of a hydroxy group in the 7-position
作者:Urs Goldener、Markus E. Scheller、Peter Mathies、Bruno Frei、Oskar Jeger
DOI:10.1002/hlca.19850680316
日期:1985.5.15
intermediate d which reacts by recombination leading to (E)-13A + B, 16, and 17A + B, or by an H-shift to the enol intermediate 38. The latter undergoes an aldol-type reaction to (E/Z)-14A + B and (E/Z)-15A + B, as well as a photochemical [2 + 2]-cycloaddition to 18. On singlet excitation (λ = 254 nm, MeCN), (E)-5 undergoes photocleavage to the carbene intermediates f and g. The vinyl carbene f reacts
描述了环氧二烯(E)-5的合成和光解。在三重态激发(λ> 280 nm,丙酮)上,(E)-5经历C(5)O键的初始裂解,导致中间体c。大概是H位移(ce),然后1,4-双自由基e的片段(通过烯醇37)断裂成二酮(E)-6和(Z)-12。可替换地裂解的C(6)C(7)的键Ç配料的双自由基中间体d其通过重组反应产生(E)-13A + B,16和17A + B,或通过H-移位反应生成烯醇中间体38。后者经历了对(E / Z)-14A + B和(E / Z)-15A + B的羟醛型反应,以及对18的光化学[2 + 2]-环加成反应。在单重态激发下(λ= 254 nm,MeCN),(E)-5发生光裂解为卡宾中间体f和g。乙烯基卡宾f与相邻的双键反应,得到环丙烯22作为主要产物。通过卡宾插入相邻的CC或CH键,从卡宾中间体g中产生化合物23、24和25。此外,起始原料的非对映异构体,环氧乙二烯(E)-20,是通过叶立德中间体h形成的。