Direct Organocatalytic Asymmetric Heterodomino Reactions: The Knoevenagel/Diels−Alder/Epimerization Sequence for the Highly Diastereoselective Synthesis of Symmetrical and Nonsymmetrical Synthons of Benzoannelated Centropolyquinanes
作者:D. B. Ramachary、K. Anebouselvy、Naidu S. Chowdari、Carlos F. Barbas
DOI:10.1021/jo049581r
日期:2004.9.1
Amino acids and amines have been used to catalyze three component hetero-domino Knoevenagel/Diels−Alder/epimerization reactions of readily available various precursor enones (1a−l), aldehydes (2a−p), and 1,3-indandione (3). The reaction provided excellent yields of highly substituted, symmetrical and nonsymmetrical spiro[cyclohexane-1,2‘-indan]-1‘,3‘,4-triones (5) in a highly diastereoselective fashion
氨基酸和胺已用于催化易得的各种前体烯酮(1a - l),醛(2a - p)和1,3-茚满二酮(3)的三组分异多米诺Knoevenagel / Diels-Alder /异构化反应。该反应以对映体选择性低至中等的高度非对映选择性提供了极高产率的高度取代的,对称和非对称的螺环己烷-1,2 -'-茚满-1',3',4-三酮(5)。芳基醛(2a - p)和1,3-茚满二酮(3)的Knoevenagel缩合反应在有机催化下提供了亚芳基1,3-茚满二酮(17),收益率很高。我们首次证明了反式-螺烷(6)对顺式螺烷(5)的氨基酸和胺催化的差向异构反应。反式-螺环烷(6)转化为顺式螺环烷5的机理显示为通过逆迈克尔/迈克尔反应进行,而不是通过分离顺式螺环烷的吗啉烯胺中间体(22)进行去质子化/再质子化。前手性顺式螺环烷(5ab)和反式螺环烷(6ab)是合成苯甲酰化的中心聚奎宁烷的极好原料。在氨基酸和胺的催化