Synthesis of New Enantiopure Bicyclic 1,2-Oxazines by Addition of Lithiated Methoxyallene to Chiral Cyclic Nitrones
作者:Robert Pulz、Stefano Cicchi、Alberto Brandi、Hans-Ulrich Reißig
DOI:10.1002/ejoc.200390169
日期:2003.3
A highly diastereoselective addition of lithiated methoxyallene 3 to chiral cyclic nitrones 1 and 2 provided N-hydroxy pyrrolidines 4 and 5, respectively, which cyclized to bicyclic 1,2-oxazines 6 and 7 by simple stirring in dilute CH2Cl2 solution. Storage of 4 in a more concentrated solution led to formation of a 60:40 mixture of 1,2-oxazine 6 and amine oxide 8. Hydroboration of 7 furnished the hydroxy-substituted
锂化甲氧基丙二烯 3 与手性环状硝酮 1 和 2 的高度非对映选择性加成分别提供了 N-羟基吡咯烷 4 和 5,通过在稀 CH2Cl2 溶液中简单搅拌,它们环化为双环 1,2-恶嗪 6 和 7。将 4 储存在更浓的溶液中导致形成 60:40 的 1,2-恶嗪 6 和氧化胺 8 混合物。 7 的硼氢化作用使羟基取代的双环 1,2-恶嗪 9 具有优异的非对映选择性。6 的氢解得到取代的吡咯烷衍生物 10。 (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)