139617-94-0Relevant articles and documents
An efficient, overall [4+1] cycloadditon of 1,3-dienes and nitrene precursors
Wu, Qiong,Hu, Jian,Ren, Xinfeng,Zhou, Jianrong
supporting information; experimental part, p. 11553 - 11558 (2011/11/29)
Intermolecular cycloadditions of conjugated dienes and nitrene precursors usually produce aziridines. A generally useful method was lacking to directly provide the [4+1] cycloadducts, 3-pyrrolines. We have realized this transformation by using an uniquely active catalyst, copper(II) 1,1,1,5,5,5-hexafluoroacetylacetonate ([Cu(hfacac)2]). The method is applicable to a wide array of dienes with good yields. When 1,4-disubsituted dienes are used as substrates, good-to-excellent cis or trans selectivity can be obtained. Interestingly, the cis or trans preference depends on the nature of the substituents, rather than diene geometry. Mechanistic studies reveal that the [4+1] cycloaddition proceeds through diene aziridination and subsequent ring expansion. Among common copper catalysts, only [Cu(hfacac)2] can efficiently catalyze both steps, which explains the unique efficiency of the catalyst.
