Pericyclic reactions of 2-pyrones with nonconjugated dienes. Conformational analysis of the double Diels-Alder adducts by molecular mechanics calculation.
作者:Kazunobu HARANO、Takashi AOKI、Masashi ETO、Takuzo HISANO
DOI:10.1248/cpb.38.1182
日期:——
Pericyclic reactions of 5-methoxycarbonyl-2-pyrone (Ic) with nonconjugated dienes (IIa-j) were investigated. The diene (Ic) reacted readily with IIa-j to give [4+2]π cycloadducts (IIIa-j) that lost carbon dioxide to afford intramolecular double Diels-Alder (DDA) adducts (V). The structures of these adducts were determined from spectral evidence. The reactivity of the addends and the regiochemistry of the primary adducts are discussed on the basis of modified neglect of diatomic overlap (MNDO) calculation data. The relative stability of the twistene- and isotwistene- type compounds and the conformation of some isotwistene-type compounds are discussed on the basis of the molecular mechanics (MM2) calculation data.
研究了5-甲氧羰基-2-吡喃酮(Ic)与非共轭二烯(IIa-j)的周环反应。二烯(Ic)与IIa-j反应生成[4+2]π环加合物(IIIa-j),随后失去二氧化碳,形成内双狄尔斯-阿尔德(DDA)加合物(V)。这些加合物的结构通过光谱证据确定。基于经修正的忽视双原子重叠(MNDO)计算数据,讨论了加合物的反应活性和初级加合物的区域化学。基于分子力学(MM2)计算数据,探讨了扭烯型和同扭烯型化合物的相对稳定性以及某些同扭烯型化合物的构象。