Cycloaddition of nitrones to free and coordinated (E)-cinnamonitrile: effect of metal coordination and microwave irradiation on the selectivity of the reaction
作者:Bimbisar Desai、Timothy N. Danks、Gabriele Wagner
DOI:10.1039/b302086j
日期:——
[2 + 3] Cycloaddition of N-methyl-C-phenylnitrone to transition metal coordinated (E)-cinnamonitrile occurs exclusively at the nitrile CN bond, leading to Δ4-1,2,4-oxadiazoline complexes, from which the heterocyclic ligand can be released and isolated in high yield. In contrast, the reaction of the nitrone with free cinnamonitrile involves the CC bond only, yielding a diastereomeric mixture of iso
[2 + 3] 环加成 的 Ñ甲基Ç -phenylnitrone过渡金属配位的(E)-肉桂腈仅在腈Ç N键,导致Δ 4 -1,2,4-恶二唑啉络合物,从其中杂环配体可以高产量释放和分离。相反,硝酮与游离基的反应肉桂腈仅涉及C C键,得到异恶唑烷-4-腈的非对映异构体混合物。微波辐照可显着提高两个转化的反应速率,而不会改变它们相对于热反应的区域选择性。他们俩腈 配体[MCl 2(肉桂腈)2 ]型的配合物中的M(M = Pt或Pd)的反应性显着不同。因此,即使在过量的硝酮存在下,短时间的微波照射也可以选择性合成单环加成产物[PtCl 2(肉桂腈)(恶二唑啉)]。使用更长的照射时间,该配合物可以进一步转化为双环加成产物[PtCl 2(恶二唑啉)2 ]。当施加热加热时,也会产生后一种化合物,但是,单环加成产物的形成在热条件下不能选择性地进行。