Highly stereoselective synthesis of (Z)-1,2-dihaloalkenes by a Pd-catalyzed hydrohalogenation of alkynyl halides
作者:Gangguo Zhu、Dongxu Chen、Yuyi Wang、Renwei Zheng
DOI:10.1039/c2cc31553j
日期:——
An unprecedented Pd-catalyzed hydrohalogenation of alkynyl halides for the regio- and stereoselective synthesis of (Z)-1,2-dihaloalkenes has been realized using [(allyl)PdCl]2 as the catalyst and cis,cis-1,5-cyclooctadiene as the ligand. The advantages of this protocol are well illustrated by the assembly of trisubstituted (Z)-enynes and multifunctional benzenes via iterative cross-coupling reactions or tandem Diels–Alder–aromatization reactions, respectively.
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。