Organocopper compounds alkenes

Organocopper compounds make c/5-addition to a simple acetylene to afford the alkenylcopper compounds and further they react with organic halides to afford cis alkenes by a coupling reaction as shown in eq. (22.34) [82-85]. 

Synthesis.— A review on organocopper compounds and organocuprates in synthesis has appeared these reagents are particularly useful for constructing olefins. Thus stereospecifically trisubstituted alkenes (381) are obtained by alkylation of vinylcopper reagents in the presence of triethyl phosphite and HMPA. The vinylcopper rea nts (382) are obtained by addition of acetylenes to a reagent prepared from R MgX and cupric bromide in ether at — 10 C. Alkylation occurs with retention of configuration... 

This procedure illustrates a general method for the preparation of alkenes from the pal 1 adium(Q)-cata1yzed reaction of vinyl halides with organo-lithium compounds, which can be prepared by various methods, including direct regioselective lithiation of hydrocarbons. The method is simple and has been used to prepare a variety of alkenes stereoselectively. Similar stoichiometric organocopper reactions sometimes proceed in a nonstereoselective... 

The 1,4-addition of a,)5-unsaturated carbonyl proceeds not only to the double bond but also to the triple bond of unsaturated carbonyl compounds. For example, a c/5-alkene is selectively obtained with an organocopper boron compound as shown in eq. (22.33) [81]. 

Finally, not all applications of Cul involve organocuprates or related reagents. For example, Corey used Cul to catalyze intramolecular diazoalkene cyclization reactions, and Yates used Cul to catalyze the Wolff rearrangement of diazo ketones. Flouse recommended CuL(SBu2)2 for the intermolecular cyclo-propanation of alkenes with a-diazo ketones. The intermediates are undoubtedly organocopper species of some kind, perhaps Cu-carbene complexes however, it should be noted that Cu and Cu are more commonly used as catalysts in conjunction with diazo compounds. ... 

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