Method for Transforming Alkynes into (E)-Dibromoalkenes

Abstract

The highly stereoselective bromination of alkynes has been realized by using copper(II) bromide as both the reacting partner and the catalyst, offering a generally efficient synthesis of (E)-dibromoalkenes. The reaction conditions are exceptionally mild, and a wide range of functional groups are well tolerated.

Polymeric CuX coordination compounds assembled from acetylenic thioether ligands RSCH2CCCH2R (R = C6H11, t-Bu): effect of the RS-group, halide and stoichiometry on the network architecture and the luminescence properties

“…More recently, the bromination of alkyne using CuBr 2 as both the reacting partner and the catalyst was also described to occur at room temperature in acetonitrile leading to the formation of ( E )-dibromoalkenes in good yields. 58 The formation of an intermediate paramagnetic π-complex was also proposed as a first step, but the second step implies the coordination of acetonitrile molecules to copper and the displacement of copper on carbon by bromide ions leading to the formation of a square planar Cu( ii )-anion. This latter transfers an electron to CuBr 2 to yield Cu( i )Br and 1 equivalent of bromide anion followed by reductive elimination (Scheme 5B).…”

Easily accessible non-aromatic heterocycles with handles: 4-bromo-2,3-dihydrofurans from 1,2-dibromohomoallylic alcohols

“…16 These were efficiently converted to E-dibromoalkenes 2 by treatment with CuBr 2 in the presence of activated molecular sieves. 17 Of note, these latter conditions were incompatible with highly electron rich aromatic compounds (e.g., p-MeOPh, thiophene).…”

Dihydroquinazolinones via A3‐Type Reactions of N‐Carbamoyliminium Ions

“…Surprisingly, they proved to be the corresponding dibrominated adducts ( 26 and 27 ). A recent report has described a similar dibromination of alkynes using CuBr 2 [41] . CuBr 2 is likely also to be the bromination agent here as it may be formed by reaction between CuBr and oxygen during workup of the A 3 ‐reaction mixture.…”

“…Ar ecent report has described as imilar dibromination of alkynes using CuBr 2 . [41] CuBr 2 is likely also to be the bromination agent herea si tm ay be formed by reaction between CuBr and oxygen duringw orkup of the A 3 -reaction mixture. It wasf ound that the amountso f26 and 27 increasedo ver time when leaving the crude reaction mixtures exposed to air and that they became the major product of the reactionafter more than 24 hhours.…”