電子供与性置換基によるベンゾシクロブテン開裂の促進効果と2,3-ベンゾジアゼピン合成への応用

抄録

Benzocyclobutenes, having a beta-silicon atom on the cyclobutene ring, were prepared and subjected to thermal electrocyclic ring-opening reaction in the presence of maleic anhydride. Various reaction conditions (temperature and time) were applied for the reaction and the yields of addition products were compared with those of corresponding alkylated benzocyclobutenes. These examinations revealed that the beta-silicon atom significantly accelerated formation of o-quinodimethane intermediates, which could be reasonably explained by sigma-donating effect of the C-Si bond toward LUMO of the cloven C-C bond in the transition state. Much more strongly electron-donating group, oxy-anion, can enforce the ring fission at lower temperature. Utilizing these advantages, a novel successive 4pi-8pi electrocyclic reaction involving diazo group was developed to produce 2,3-benzodiazepines under extremely mild reaction conditions.

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