Camphor-Derived, Chelating Auxiliaries for the Highly Diastereoselective Intermolecular Pauson−Khand Reaction: Experimental and Computational Studies
作者:Xavier Verdaguer、Jordi Vázquez、Gerard Fuster、Vania Bernardes-Génisson、Andrew E. Greene、Albert Moyano、Miquel A. Pericàs、Antoni Riera
DOI:10.1021/jo9809985
日期:1998.10.1
specifically designed as chiral auxiliaries suitable for chirality transfer to cobalt in Pauson-Khand reactions, has been synthesized. The dicobalt hexacarbonyl complexes of the alkoxyacetylenes derived from these alcohols (10a-12a) can be converted to the rather stable, internally chelated, pentacarbonyl complexes 10b-12b by treatment with NMO. The intermolecular Pauson-Khand reactions of 10b-12b with strained
对映体纯的(2R)-10-(烷硫基)异冰片醇[甲硫基(1),新戊硫基(2),苯硫基(3)],专门设计为适合在Pauson-Khand反应中从手性转移至钴的手性助剂已合成。通过用NMO处理,可以将衍生自这些醇(10a-12a)的烷氧基乙炔的二钴六羰基配合物转化为相当稳定的,内部螯合的五羰基配合物10b-12b。10b-12b与应变烯烃的分子间Pauson-Khand反应在低温(低至-20摄氏度)下以合成有用的速率发生,具有高收率和非对映选择性:降冰片烯(77%; 92:8),降冰片二烯(82 %; 96; 4),双环[3.2.0]庚-6-烯(91%; 93:7)。10b与降冰片二烯加成物的主要非对映异构体14 已被用作合成(S)-(-)-4-烷基-2-环戊烯酮的起点,该序列由完全非对映选择性的共轭物加成,还原性裂解和手性助剂的回收率(> 95%)组成,和复古的Diels-Alder反应。通过结合半经验[PM3(tm)]