Rhodium-Catalyzed Enantioselective Radical Addition of CX<sub>4</sub>
Reagents to Olefins
作者:Bo Chen、Cheng Fang、Peng Liu、Joseph M. Ready
DOI:10.1002/anie.201704074
日期:2017.7.17
We describe the synthetically useful enantioselective addition of Br−CX3 (X=Cl or Br) to terminal olefins to introduce a trihalomethyl group and generate optically active secondary bromides. Computational and experimental evidence supports an asymmetric atom‐transfer radical addition (ATRA) mechanism in which the stereodetermining step involves outer‐sphere bromine abstraction from a [(bisphosphine)RhIIBrCl]
我们描述了Br-CX 3(X = Cl或Br)的合成有用的对映选择性加成到末端烯烃中以引入三卤甲基并生成光学活性的仲溴化物。计算和实验证据支持不对称原子转移自由基加成(ATRA)机理,其中立体确定步骤涉及通过苄基自由基中间体从[(bisphosphine)Rh II BrCl]络合物中提取外层溴。这种机理在不对称催化中显得空前。
Nucleophilic attack on halogeno(phenyl)acetylenes by halide ions
Nucleophilicreactions between halogeno(phenyl)acetylenes and halide ions, ArCCX + Y–, where Ar = C6H5 or p-ClC6H4, X = Cl or Br, and Y = Cl or Br, have been examined. Halogen exchange of the Finkelstein type was observed for the first time in acetylenehalides in anhydrous dimethyl sulphoxide when X = Br and Y = Cl. This exchange did not occur with other X–Y combinations. In the presence of up to
研究了卤代(苯基)乙炔与卤离子ArC CX + Y –的亲核反应,其中Ar = C 6 H 5或对-ClC 6 H 4,X = Cl或Br,Y = Cl或Br。当X = Br和Y = Cl时,首次在无水二甲基亚砜中的乙炔卤化物中观察到Finkelstein类型的卤素交换。其他X–Y组合未发生这种交换。在二甲基亚砜中有多达20%的水存在下,或在水-有机相转移催化条件下,所有研究的X-Y组合都发生了亲核加成反应(正式为HY)。此外,亲核试剂Y –总是攻击结合苯基的碳。HY加成的方式是立体专一性反式; 因此,所得的二卤代苯乙烯总是具有(Z)-1,2-二卤代构型。
Reactions of hot halomethyl radicals
作者:P. Cadman、J. P. Simons
DOI:10.1039/tf9666200631
日期:——
The chemical behaviour of excited halomethyl radicals, produced through photolysis of several polyhalomethanes, has been investigated in the gas phase at room temperature. It has been demonstrated that the radicals are extremely reactive in atom abstraction reactions, and the relative probability of H atom transfer and energy transfer, in collisions of excited CCl3 radicals with hydrocarbons, has been estimated. It is proposed that reactions involving the CCl radical play a major role in the photodecomposition of CHCl2Br.
研究了室温下气相中通过光解几种多卤甲烷而产生的激发卤甲基自由基的化学行为。研究表明,这些自由基在原子抽取反应中的反应性极强,并估算了激发的 CCl3 自由基与碳氢化合物碰撞时 H 原子转移和能量转移的相对概率。据推测,涉及 CCl 自由基的反应在 CHCl2Br 的光分解中起着重要作用。