Intramolecular low-temperature 1,3-dipolar cycloadditions of nitrones: synthesis of chromano-heterocycles
作者:Gurpinder Singh、M.P.S. Ishar、Vivek Gupta、Gurmit Singh、Mohit Kalyan、Surinderjit Singh Bhella
DOI:10.1016/j.tet.2007.03.086
日期:2007.5
the reported facile intramolecular 1,3-dipolar cycloadditions of in-situ generated nitrone on heterocyclic systems, reactions of 2-(N-allyl/crotyl/cinnamyl-anilino)-3-formylchromones with N-phenyl-/methylhydroxylamine under comparable conditions, afford fused isoxazolidines only in low to moderate yields; the corresponding amides derived from rearrangement of in situ generated nitrones are formed as
与已报道的在杂环体系上原位生成的硝酮的分子内分子内1,3-偶极环加成反应相反,2-(N-烯丙基/巴豆基/肉桂基-苯胺基)-3-甲酰基色酮与N-苯基-/甲基羟胺的反应在可比较的条件下,仅以低至中等的产率得到稠合的异恶唑烷;从原位生成的硝酮重排得到的相应酰胺形成为主要产物。但是,当通过在冰冷的温度下在二氯甲烷中搅拌反应物进行反应时,高度立体选择性的分子内1,3-偶极环加成反应会以高收率(80-90%)产生新颖的稠合异恶唑烷。