Remarkable dipolarophilicity of nitrile function uncovered in the 1,3-dipolar cycloaddition reaction of homoadamantane-incorporated nitrones. A direct and facile route to Δ4-1,2,4-oxadiazoline (2,3-dihydro-1,2,4-oxadiazole) derivatives
通过用SeO 2 / H 2 O 2氧化4-氮杂高锰金刚烷5、6,获得并入高金刚烷环系统中的桥连硝酮7、8。这些硝酮与缺电子炔烃的1,3-偶极环加成反应在0°Cr时进行区域特异性反应。t。得到4-取代的异恶唑啉。与苯乙炔的反应需要强制性条件,其中使用偶极亲和剂作为溶剂从7中获得5取代的异恶唑啉9d,并在较高的反应温度下由8直接形成重排吡咯12d。酮硝酮生成的环加合物将8个进一步转化为高金刚烷稠合的吡咯。在这种情况下,通过不同的机理从相同的原料分别获得2-取代的和3-取代的吡咯12a和12e。前者在质子溶剂中通过酰基氮丙啶途径通过热分解而产生,而后者通过烯胺途径在质子溶剂中产生。
Synthesis of 2-aza-3-oxatetracyclo [7. 3. 1. 17,11. 02,6]tetradecane derivatives by the 1,3-dipolar cycloaddition reaction of homoadamantane-incorporated nitrones with alkenes
The 1,3-dipolar cycloaddition reaction of homoadamantane-incorporated nitrones, 4-azahomoadamant-4-ene-N-oxide (1) and 5-methyl-4-azahomoadamant-4-ene N-oxide (2), with various alkenes afforded 2-aza-3-oxatetracyclo[7.3.1.1(7,11).0(2,6)]tetradecane derivatives as the 1:1 cycloadduct. The reaction showed relatively low regio- and stereo-selectivities, however only the 5-endo adduct was not formed. This was rationalized by the steric effect in the course of reaction process on the basis of PM3 calculations of the transition state model. (C) 1997 Elsevier Science Ltd.
Synthesis of 4-azahomoadamant-4-ene N-oxides and their 1,3-dipolar cycloaddition reactivity1
作者:Yang Yu、Masatomi Ohno、Shoji Eguchi
DOI:10.1016/s0040-4039(00)93509-3
日期:1991.9
Nitrones incorporated in a homoadamantane ring system, which were obtained by SeO2-H2O2 of 4-azahomoadamantane, underwent 1,3-dipolar cycloaddition reaction with electron-deficient alkynes (not with alkenes) to give 4-substituted isoxazoline specifically by steric reasons.