The Rational Synthesis of Chlorins via Rearrangement of Porphodimethenes: Influence of β-Substituents on the Regioselectivity and Stereoselectivity of Pyrroline Ring Formation
作者:Dennis H. Burns、Yue H. Li、Dong C. Shi、Timothy M. Caldwell
DOI:10.1021/jo020105f
日期:2002.6.1
density, with an electron-neutral hydrogen or an electron-withdrawing carbonyl beta-substituent demonstrating the greatest influence on the formation of the pyrroline ring. The synthesis is highly stereoselective when epimerization of the pyrroline ring beta-carbons is possible, furnishing only the trans-reduced sterioisomer. Finally, there is substantial evidence that a fifth, axial ligand is involved
本文报道的二甲亚砜重排方法提供了从易得的吡咯前体中合理,分步合成二氢卟酚的方法。中间体二氧戊二烯可直接通过“ 2 + 2”麦克唐纳缩合反应,或由三吡喃和双甲酰基吡咯的对称性较小的“ 3 +1”缩合反应提供。合成途径短且高度收敛,特别是在“ 3 +1”方法的情况下,并以良好至中等的产率提供二氢卟酚。合成具有很高的区域选择性,并且似乎基于β取代基稳定过量电子密度的能力,其中电子中性氢或吸电子羰基β取代基对吡咯啉环的形成影响最大。当吡咯啉环β-碳的差向异构化是可能的时,该合成是高度立体选择性的,仅提供反式还原的立体异构体。最终,有充分的证据表明,在pi系统从金属卟啉二甲到金属氯霉素的重排过程中,第五个轴向配体参与了外围氢的移位。