Fleming Fraser F, Wei Yunjing, Liu Wang, Zhang Zhiyu
Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530,
Tetrahedron. 2008 Aug 4;64(32):7477-7488. doi: 10.1016/j.tet.2008.05.110.
Stereodivergent cyclizations of gamma-hydroxy cyclohexanecarbonitriles are controlled simply through judicious choice of cation in the alkylmetal base. Deprotonating a series of cyclic gamma-hydroxy nitriles with i-PrMgBr generates C-magnesiated nitriles that cyclize under stereoelectronic control to cis-fused hydrindanes, decalins, and bicyclo [5.4.0] undecanes. An analogous deprotonation with BuLi triggers cyclization to trans-fused hydrindanes, decalins, and bicyclo [5.4.0] undecanes consistent with a sterically controlled electrophilic attack on an equatorial nitrile anion. Using cations to control the geometry of metalated nitriles provides a versatile, stereodivergent cyclization to cis- and trans-hydrindanes, decalins, and [5. 4. 0] undecanes, and reveals the key geometric requirements for intramolecular S(N)2 and S(N)2' displacements.
γ-羟基环己烷甲腈的立体发散性环化反应可通过在烷基金属碱中明智地选择阳离子来简单控制。用异丙基溴化镁对一系列环状γ-羟基腈进行去质子化反应，生成碳镁化腈，这些碳镁化腈在立体电子控制下环化生成顺式稠合的氢化茚、十氢化萘和双环[5.4.0]十一烷。用丁基锂进行类似的去质子化反应会引发环化生成反式稠合的氢化茚、十氢化萘和双环[5.4.0]十一烷，这与对赤道面腈阴离子的空间控制亲电攻击一致。利用阳离子控制金属化腈的几何结构，可实现对顺式和反式氢化茚、十氢化萘和[5.4.0]十一烷的通用立体发散性环化反应，并揭示了分子内S(N)2和S(N)2'取代反应的关键几何要求。
