Domino routes to substituted benzoindolizines: tandem reorganization of 1,3-dipolar cycloadducts of nitrones with allenic esters/ketones and alternative cycloaddition–palladium catalyzed cyclization pathway
作者:Ashish Kapur、Kamal Kumar、Lakhwinder Singh、Parminder Singh、Munusamy Elango、Venkatesan Subramanian、Vivek Gupta、Priyanka Kanwal、Mohan Paul S. Ishar
DOI:10.1016/j.tet.2009.03.076
日期:2009.6
intramolecular aza Diels–Alder reaction in the intermediate C. DFT calculations of various parameters for diene and dienophile components in the proposed intermediate C have revealed that conformational constraints imposed by the alkyl groups (R=Me, Et) favor intramolecular aza-Diels–Alder cycloaddition. An alternative domino route to benzoindolizines (9a,d,g) involving sequential one-pot cycloaddition of azadienes
的反应Ç - (4-氧代-4- ħ [1]苯并吡喃-3-基) - ñ -苯基硝酮(7)与丙二烯酯(8A - C ^)和丙二烯酮类(18A - d)配料benzoindolizines(9A - ķ,19a – d),收益率很高。假定苯并吲哚并嗪的形成涉及将烯丙基酯/酮的C2-C3π键上的1,3-偶极区域选择性加成,然后环加合物进行多米诺转化,这涉及中间体C中的分子内氮杂Diels-Alder反应。对拟议的中间体C中二烯和亲二烯体组分的各种参数的计算表明,烷基(R = Me,Et)施加的构象约束有利于分子内氮杂-Diels-Alder环加成反应。苯并吲哚并嗪(9a,d,g)的另一种多米诺途径涉及将氮杂二烯(22a – c)与甲硅烷基烯醇醚(23)相继进行一锅环加成反应),然后进行钯(0)催化的Heck偶联反应。这两种方法都代表了合成苯并吲哚并嗪的新颖多米诺路线。