Organocopper reagents reactions

In contrast to reactions of all other organocopper reagents, reactions of copper(I) acetylides with propargylic substrates result in regiospecific a-substitution. This procedure for the preparation of 1,4-diynes has proven useful in pheromone synthesis. ... 

Hudrlik, P. R, Ma, D., Bhamidipati, R. S. and Hudrlik, A. M. 1996. Ring-opening reactions of a- and P-epoxy silanes with organocopper reagents Reaction at carbon or silicon. J. Org. Chem. 61 8655-8658. 

Direct transmetalation of organoboranes to organocopper reagents is not a general reaction. Because of dieir similar bond energies and electronegativities, diis trans-nietalation is linided to die preparation of alkenylcopper and unfiinctionalized... 

To explain tlie stereodieniistiy of tlie allylic substitution reaction, a simple stereoelectronic model based on frontier molecular orbital considerations bas been proposed fl55. Fig. G.2). Organocopper reagents, unlike C-nudeopbiles, possess filled d-orbitals fd - configuration), wbidi can interact botli witli tlie 7t -fC=C) orbital at tlie y-carbon and to a minor extent witli tlie cr -fC X) orbital, as depicted... 

Hydrolysis of tlie ctioI etliers obtained from tlie substitution reaction witli tlie organocopper reagent yielded diiral -substituted aldehydes witli ees of 62 and 7396 for tlie Su2" and S 2 products, respectively. 

Scheme 2.30 Ring-opening reaction with organocopper reagents to form (E)-allyl 111 amines.

Scheme 2.31 Stereochemical course of ring-opening reactions with organocopper reagents.

With respect to the nucleophilic addition of organocopper reagents, a sharp contrast between the rigid isopropylidene glyceraldehyde and its open-chained analog, 2,3-bis(benzyloxy)propanal. was observed (compare Tables 15 and 16). With the isopropylidene-protected aldehyde a high syn diastereoselectivity could only be obtained when tetrahydrofuran was used as reaction solvent, and the diastereoselectivity dropped considerably in diethyl ether. In contrast, the latter solvent allows excellent syn selectivities in additions to the dibenzyl-protected glyceraldehyde81. On the other hand, tetrahydrofuran yields better results than diethyl ether in the... 

Alkylallenes are obtained by the reaction of 1-ethynylcycloalkanol acetates with organocopper reagents, lithium dimethyl- and dibutylcuprates643 (see Section B.l). Even in the case of the presence of a substituent at the acetylenic terminus, SN2 displacement takes place, giving tetra-substituted allenes. Reaction of the steroidal 17-acetoxy-17-ethynyl derivative la shows that the... 

---