Carbomagnesiation reactions

II. CARBOMAGNESIATION REACTIONS OF ALKYNES A. Intramolecular Addition to Simple Alkynes... 

Since this report on the copper catalysis in carbomagnesiation across acetylene, a variety of Cu-catalyzed carbomagnesiation reactions of afkynes have been reported. However, the applicable aUcynes are somewhat limited to electronically biased (activated) or heteroatom-containing aUcynes, which will be discussed later. 

Chromium salts can catalyze the carbomagnesiation reactions of 1,6-enynes with cy-clization (Scheme 12) . This reaction is probably initiated by carbometalation of the alkyne unit. The resultant organomagnesium species 16 undergoes further functionalization upon treatment with various electrophiles (Scheme 12) . ... 

The carbomagnesiation reaction proceeds with a range of organomagnesium compounds (Scheme 30) °. Not only aryl, alkenyl and aUcynyl groups, but also alkyl groups were found to add across a triple bond. The enhanced reactivity of cyano-substituted alkynes is worthwhile, and this may be due to accelerated alkyl transfer from 53 with activation of the cyano group by MgX2 (Scheme 29). 

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