Highly stereoselective synthesis of (Z)-1,2-dihaloalkenes by a Pd-catalyzed hydrohalogenation of alkynyl halides

Abstract

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.

Metal‐Catalyzed Hydrofunctionalization Reactions of Haloalkynes

“…A reaction pathway involving the initial trans ‐halopalladation of the alkyne to give an alkenyl‐palladium intermediate, which evolves into the final product by protonolysis, was proposed by the authors. The process proved to be effective for the preparation of a variety of ( Z )‐1,2‐dichloroalkenes, ( Z )‐1‐bromo‐2‐chloroalkenes and ( Z )‐1,2‐dibromoalkenes through the hydrochlorination or hydrobromination of both chloro‐ and bromoalkynes, but resulted inoperative for the hydrochlorination of iodoalkynes and the hydroiodination of chloroalkynes …”

Crystal structures of (E)-3-(furan-2-yl)-2-phenyl-N-tosylacrylamide and (E)-3-phenyl-2-(m-tolyl)-N-tosylacrylamide

“…The Cu-catalysed azide-alkyne cycloaddition (CuAAC) reaction constitutes one of the most interesting examples of the click reaction (Bae et al, 2005;Cheng et al, 2012;Mondal & Pan, 2015). Trisubstituted alkenes are commonly found in the molecular skeleton of natural products and bioactive substances, and they are important building blocks in organic chemistry (Zhu et al, 2012;Manikandan & Jeganmohan, 2015). Therefore, it is highly desirable to develop new efficient and general methods for the stereoselective synthesis of trisubstituted alkenes (Ram & Tittal, 2014;Bae et al, 2005).…”

Chloride-Tolerant Gold(I)-Catalyzed Regioselective Hydrochlorination of Alkynes

“… 4 Compared to the traditional syntheses of vinyl chlorides, such as halogenations of carbonyl compounds 5 and electrophilic chlorination of alkynes, 6 the direct hydrochlorination of alkynes from HCl is a straightforward and atom-economic method. However, given that HCl itself is a dangerous gas and handling is problematic, synthetic chemists have focused on indirect hydrochlorination strategies for activated alkynes, 7 using RCOCl, TMSCl, or metal chlorides as chlorine sources ( Scheme 1 a). 8 One notable example is the recent work by Engle and co-workers on the palladium-catalyzed anti -hydrochlorination of alkynes using a directing group ( Scheme 1 b).…”