Organocopper reagents higher-order

Associated with the propensity to intramolecular delivery of the organocopper reagent is the benefit of high regioselectivity, since an intramolecular trajectory prohibits the alternative a-attack. This is best exemplified by the reaction behavior of the cyclic system 161 (Scheme 6.33). For this substrate, y-attack is sterically hindered. Hence, treatment of the acetate of 161 with a higher order methyl cuprate... 

Mechanistic aspects of copper-catalyzed Grignard addition to a,/ -unsaturated carbonyl compounds have not attracted much attention, probably because of the complex nature of the reagent system [11], but it would resemble that of the 1,4-addition of stoichiometric or higher-order organocopper reagents that have been investigated extensively [15,18,223]. 

The organocopper reagents used for conjugate additions to enones are homocuprates, heterocuprates, higher-order cuprates, and Grignard reagents in the presence of catalytic amounts of copper salts (CuX). 

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