Alkynes organocopper compounds

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. ... 

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... 

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 ... 

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... 

The authors found that the addition of TMEDA before oxidation was necessary to increase both reproducibility and yields of this sequential process, presumably due to the inhibition of the oxidative dimerization [98], a side reaction known in the chemistry of organocopper compounds. Alkynes with electron-withdrawing groups directly bound to the sp carbon were also employed in the stereoselective carbocupration [99]. For example, the carbocupration of alkynoates 341 promoted by Lewis acids, such as trimethylsilyl triflate, leads to the isomeric TMS-allenoate compounds, which on hydrolysis or a Mukaiyama-type aldol reaction produce the corresponding di- and trisubstituted acrylates 342 (Scheme 10.116) [100]. 

Copper tends to form more stable organocopper compounds with acetylene compounds than with aryl compounds. The synthetic reaction of acetylenic compounds with copper or copper salt, e.g., the Cadiot-Chodkiewics and Glaser reactions are well known. The Cadiot-Chodkiewics reaction is a reaction where I-bromoalkyne easily reacts with a terminal alkyne in the presence of a catalytic amount of a cuprous salt or amines to afford conjugate diacetylene compounds in high yield [43]. For example, polyacetylene is easily synthesized as shown in eq. (22.19) [43],... 

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],... 

Formation of metal-carbon bonds by addition of an organometallic reagent to an unsaturated compound or a diazonium compound is a little-used method in organocopper chemistry. Various alkylcopper reagents, (RCu + MgXg or LiX), add to acetylene or the alkynes, RC=CH, in a cis manner in ether or ether-pentane at low temperatures (223). A 7T-complex is a probable intermediate. The vinylcopper addition product obtained is dependent on the nature of the alkyne, being sensitive to electronic effects in the latter ... 

The conjugate additions of organocoppers to a,(3-unsaturated carbonyl compounds, among them alkynes, have been reviewed. These generally show a syn preference and are directed in the Michael sense (equation 200) . Similar alkyl... 

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