作者:O. M. Nikitin、G. V. Gavrilova、T. V. Magdesieva
DOI:10.1007/s11172-007-0152-7
日期:2007.5
Processes of direct and electrocatalytic (in the presence of electrochemically reduced Cp2TiCl2) reduction of three α-bromoketones containing the C(sp3)-Br or C(sp2)-Br bond, viz., 2-bromo-and 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-ones and α-bromo-acetophenone, were studied by cyclic voltammetry and preparative electrolysis. In all cases, the dissociative electron transfer proceeds via the concerted mechanism. Preparative electrolysis of these α-bromoketones in the presence of Cp2TiCl2 affords the reductive debromination products in 40–80% yield at low cathodic potentials (−0.85 V vs. Ag/AgCl/KCl). In the case of 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-one in the potentiostatic regime, only one bromine atom can be eliminated selectively.
通过循环伏安法和制备电解法研究了直接还原和电催化还原(在电化学还原的 Cp2TiCl2 存在下)三种含有 C(sp3)-Br 或 C(sp2)-Br 键的α-溴酮,即 2-溴和 2,6-二溴-4,4-二甲基环己-2,5-二烯-1-酮和α-溴-苯乙酮的过程。在所有情况下,解离电子转移都是通过协同机制进行的。在 Cp2TiCl2 的存在下,制备电解这些 α-溴酮,在低阴极电位(-0.85 V 对 Ag/AgCl/KCl)下可得到 40-80% 的还原脱溴产物。在恒电位条件下,2,6-二溴-4,4-二甲基环己-2,5-二烯-1-酮只能选择性地消除一个溴原子。