Developing a Diastereoselective Intramolecular [4 + 3] Cycloaddition of Nitrogen-Stabilized Oxyallyl Cations Derived from <i>N</i>-Sulfonyl-Substituted Allenamides
作者:Andrew G. Lohse、Richard P. Hsung、Mitchell D. Leider、Sunil K. Ghosh
DOI:10.1021/jo200147h
日期:2011.5.6
Efforts toward achieving a practical and diastereoselective intramolecular [4 + 3] cycloaddition of nitrogen-stabilized oxyallyl cations with tethered dienes are described. Epoxidation of N-sulfonyl substituted allenamides with dimethyldioxirane (DMDO) generates nitrogen-stabilized oxyallyl cations that readily undergo stereoselective [4 + 3] cycloaddition with dienes. Selectivity is found to depend
描述了实现氮稳定氧烯丙基阳离子与系链二烯的实用和非对映选择性分子内 [4 + 3] 环加成的努力。N-磺酰基取代的丙二烯酰胺与二甲基二环氧乙烷 (DMDO) 的环氧化生成氮稳定的氧烯丙基阳离子,这些阳离子很容易与二烯进行立体选择性 [4 + 3] 环加成。发现选择性取决于束缚长度以及氧烯丙基阳离子中间体的稳定性,无论是由N-氨基甲酰基-或N-磺酰基-取代的烯丙酰胺产生的。手性N-的用途磺酰基取代的丙二烯酰胺在环加成反应中提供了最小的非对映选择性,而通过存在于系链上的立体中心可以实现高非对映选择性。这些研究为烯丙酰胺的合成效用提供了进一步的支持。