The structure and electronic nature of the phosphine have a significant influence on not only the formation, but also the subsequent transformation of O,P-acetals. The O,P-acetals generated from tris(o-tolyl)phosphine [(o-tol)3P] underwent efficient substitution reactions with various nucleophiles.
Efficient Activation of Acetals, Aldehydes, and Imines toward Silylated Nucleophiles by the Combined Use of Catalytic Amounts of [Rh(COD)Cl]<sub>2</sub>and TMS-CN under Almost Neutral Conditions
In the presence of a catalytic amount of a transition metal compound such as [Rh(COD)Cl]2, Co(acac)2, or NiCl2, trimethylsilyl cyanide smoothly reacts with acetals to form α-methoxy carbonitriles in good yields. In the coexistence of catalytic amounts of [Rh(COD)Cl]2 and TMS-CN, silyl enol ethers or ketene silyl acetals react with acetals, aldehyes, or imines to yield the corresponding coupling products in good yields under almost neutral conditions.
Vinylethers can be protonated to generate oxocarbenium ions that react with Me3SiCN to form cyanohydrin alkylethers. Reactions that form racemic products proceed efficiently upon conversion of the vinylether to an α-chloro ether prior to cyanide addition in a pathway that proceeds through Brønsted acid-mediated chloride ionization. Enantiomerically enriched products can be accessed by directly protonating
乙烯基醚可以质子化以生成氧代碳正离子,该离子与 Me 3 SiCN反应形成氰醇烷基醚。在通过布朗斯台德酸介导的氯离子电离进行的途径中,在加入氰化物之前将乙烯基醚转化为 α-氯醚后,形成外消旋产物的反应有效进行。可以通过用手性布朗斯台德酸直接质子化乙烯基醚以形成手性离子对来获得对映体富集的产品。Me 3 SiCN 作为亲核试剂,PhOH 在不对称双分子亲核加成到氧碳鎓离子的罕见例子中作为化学计量质子源。计算研究为催化剂和氧代碳正离子之间的相互作用提供了模型。
A Sterically Congested α-Cyanoamine as a Cyanating Reagent: Cyanation of Acetals and Orthoesters
The cyanation of acetals and orthoesters by using a stericallycongestedα-cyanoamine as a cyanatingreagent was investigated. The α-cyanoamine effectively facilitated cyanation in the presence of trichlorosilyl triflate to produce a variety of cyanated adducts in excellent yields. Analysis of the reaction mixture by 1H NMR spectroscopy revealed that trichlorosilyl triflate produced an oxocarbenium
研究了使用空间拥挤的 α-氰胺作为氰化试剂对缩醛和原酸酯进行氰化。α-氰基胺在三氟甲磺酸三氯甲硅烷酯存在下有效促进氰化,以优异的产率生产各种氰化加合物。通过 1 H NMR 光谱分析反应混合物表明,三氟甲磺酸三氯甲硅烷基酯产生作为中间体的氧代碳鎓阳离子物质。