Alkynes organocoppers

When X=OH, this conversion of acetylenic alcohols to unsaturated aldehydes or ketones is called the Meyer-Schuster rearrangement The propargyl rearrangement can also go the other way that is, 1-haloalkenes, treated with organocopper compounds, give alkynes. ... 

For the addition of organocopper reagents to alkynes and conjugated dienes, see 15-23. 

Alkynylcoppers constitute a class of compounds relevant to several synthetic organic reactions,47 where they have been proposed as key intermediates. The interest in this area has supposed that the number of structurally characterized alkynylcopper complexes has considerably expanded in the last few years. The most common route toward alkynylcoppers is based on the reaction of a terminal alkyne with a copper source, either a salt or an organocopper compound (Equations (8) and (9)). 

Generally, organocopper compounds can be prepared by transmetallation between copper salts and organometallic reagents such as RLi, RMgX, and RZnX.53,53a,53b Copper alkynides can be obtained by reaction of terminal alkynes... 

This is an alkyne-analog of the Wittie reaction. Since organocopper chemistry finds utility in converting the C-Br bond to other alkyl groups, we show only the first part of the transformation in most examples. 

When the CuBr-SMe2 complex is used in preparing the organocopper reagent, and Me2S is a cosolvent in the addition, higher yields may be achieved. Under such conditions even the otherwise unreactive methylcopper adds to terminal alkynes to generate 2-methyl-susbtituted alkenylcopper derivatives.520... 

For addition reactions involving vinylic copper reagents derived from organocopper additions to alkynes, see page 452, Section 2.28. 

The conjugate addition of organocopper reagents to ot,(3-alkynic esters, ketones, aldehydes and acids is a useful method for the preparation of various tri- and tetra-substituted alkenes,87 although addition to aldehydes is less common.88 Use of a vinylcuprate results in the formation of a conjugated dienone, which further highlights the importance of this methodology (equation 43 ).87... 

When alkynic esters are used as substrates in the reaction sequence, activated alkenes of good isomeric purity can be prepared. Initiation of the difunctionalization usually is by means of organocopper-medi-ated 1,4-addition, which proceeds via carbometallation of the alkynyl moiety of the ester to give a vi-nylcopper intermediate, (14). Trapping by an electrophile affords cis-difunctionalized alkenoates... 

As a last example of an uncatalyzed C,C coupling of a neutral organocopper compound Figure 16.9 depicts the alkynylation of a copper acetylide with a bromoalkyne which is easily accessible via bromination of a terminal alkyne ... 

I. B. Campbell, The Sonogashira Cu-Pd-Catalyzed Alkyne Coupling Reactions, in Organocopper Reagents A Practical Approach (R. J. K. Taylor, Ed.), 217, Oxford University Press, Oxford, U. K., 1994. 

The carbocupration of alkynes, that is, the addition to a non-activated C-C triple bond, is another classical reaction of organocopper compounds. Due to the high regioselectivity and m-stereoselectivity usually observed in... 

Copper(i) catalysis of the addition of organomagnesium compounds to alkynes has been observed, but stoichiometric organocopper reagents, derived from organomagnesium compounds, are more effective in the absence of other activating features [4],... 

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