Hypervalent Interactionsin the Reactions Onium Salts of Main Group Elements

1-十一烯基(苯基)碘盐与卤离子反应，生成完全转化的取代产物和n-消除产物。对卤化物浓度的紫外光谱和动力学分析表明，这些反应是通过在快速预平衡状态下形成的高价中间体--3-卤代碘烷进行的。相反，2-卤代-1-癸烯基碘盐的取代产物完全保持构型不变。该反应是通过中间体卤代碘的配体偶联反应进行的，苯基苯基碘盐的溶剂分解生成了保留和转化两种取代产物。氚标记实验表明，同位素在保留产物的α和β位置之间完全扰乱，而不是反转产物。这些结果表明，保留产物是通过乙烯基苯离子形成的，而反转是通过面内S_N_2机理发生的。α-β，β-二烷基-乙烯基碘盐在溶剂分解以及与卤离子的反应中产生了各种β-烷基重排的产物。烷基转变为离开的碘基比顺式基团更容易重排，但顺式基团的重排幅度较大。未重排取代产物的形成不是立体专一性的。这些结果与主要通过β-烷基参与并以伯烯酸阳离子为中间体的反应是一致的。1-金刚烷基硫酸盐与卤化物离子的反应速率随卤化物浓度的增加而增加，遵循饱和曲线。这强烈地表明，在该反应过程中形成了高价卤代呋喃。

Reactions of 1-decenyl (phenyl) iodonium salt with halide ions gave substitution products of complete inversion as well as n-elimination products. Analyses of UV spectroscopic and kinetic dependences on the halide concentrations show that the reactions occur via a hypervalent intermediate, lambda^3-haloiodane, formed in a rapid pre-equilibrium. By contrast, 2-halo-1-decenyl-iodonium salts gave substitution products of complete retention of configuration. This reaction is concluded to proceed via a ligand-couplingmechanism within an intermediatehaloiodane.Solvolysis of styryl (phenyl) iodonium salt gave substitution products of both retention and inversion. Deuterium labeling experiments show that complete scrambling of the isotope between alpha and beta positions of the retention product but not of the inversion product. These results imply that the retention product is formed through a vinylenebenzenium ion while the inversion occurs by the in-plane S_N2 mechanims.ALPHAbeta, beta-dialkylvinyliodonium salt gave a variety of products of extensive rearrangement of the beta-alkyI groups on solvolysis as well as reactions with halide ions. The alkyl group trans to the leaving iodonio group rearranges more readily than the cis group, but the cis group does rearrange significantly. Formation of the unrearranged substitution products is not stereospecific. These results are compatible with a reaction occurring mainly via beta-alkyl participation accompanied by a primary vinylic cation as an intermediate.Rates for the reactions of 1-adamantylsulfonium salt with halide ions increase with halide concentration following a saturation curve. This strongly suggests intermediate formation of a hypervalent halosulfurane during this reaction.