Preparation of gem-dimethylcyclopropane-fused compounds through sigmatropic rearrangements. On/off-switching of the tautomerization of 3,4-homotropilidene by steric hindrance
作者:Tohru Futagawa、Norio Nishiyama、Akira Tai、Tadashi Okuyama、Takashi Sugimura
DOI:10.1016/s0040-4020(02)01193-6
日期:2002.11
Cyclopropanation of 4,8,8-trimethylcycloheptatriene having an ether function at the 3-position by unsubstituted carbenoid addition resulted in a complex mixture mainly due to quick valence tautomerization of the produced 3,4-homotropilidene analogue during the reaction. Dihalocarbene addition to the same substrate proceeded exclusively at the 3,4-position to give an adduct, where the tautomerization
通过未取代的类胡萝卜素的加成,在3-位具有醚功能的4,8,8-三甲基环庚三烯的环丙烷化反应形成复杂的混合物,这主要是由于反应过程中生成的3,4-同噻二烯类似物的快速价互变异构。将二卤卡宾仅在3,4-位置加成至同一底物即可生成加合物,其中互变异构过程因卤素取代基引起的位阻而中断。通过还原除去卤素原子促进了互变异构,得到了宝石-二甲基环丙烷稠合的产物。通过获得光学纯态的产物也证明了互变异构的立体特异性。