Allenyl(vinyl)methane Photochemistry. Photochemistry of Methyl 4,4-Dimethyl-2,5,6-heptatrienoate Derivatives
作者:Takashi Tsuno、Kunio Sugiyama
DOI:10.1246/bcsj.72.519
日期:1999.3
6-heptatrienoate (3a) competitively underwent E–Z geometric isomerization and intramolecular [2+2] cycloaddition, though prolonged irradiation led to [2+2] cycloadducts as main products. For methyl (E)-4,4,7-trimethyl-2,5,6-octatrienoate (3b), the intramolecular [2+2] cycloaddition occurred under both direct and sensitized irradiation and the E–Z geometric isomerization scarcely occurred. In these allenyl(vinyl)methanes
[2-(1,2-丙二烯基)-取代亚烷基]丙二酸酯的直接和敏化光解主要产生分子内[2+2]环加合物。另一方面,(E)-4,4-二甲基-2,5,6-庚三烯酸甲酯 (3a) 的直接辐照竞争性地经历了 E-Z 几何异构化和分子内 [2+2] 环加成,尽管长时间辐照导致以[2+2]环加合物为主要产物。对于 (E)-4,4,7-三甲基-2,5,6-辛三烯酸甲酯 (3b),分子内 [2+2] 环加成在直接照射和敏化照射下均发生,并且几乎不发生 E-Z 几何异构化。在直接照射下的这些丙二烯基(乙烯基)甲烷中,1,2-丙二烯基取代的酯产生作为次要产物的1,2-丙二烯基环丙烷或(2-亚乙烯基环丙基)乙酸酯。当在甲苯中的硒化氢存在下照射 3b 时,形成环戊烯。环戊烯的形成表明双自由基中间体是环戊烷-1,3-二基。通过 MO...