Lithium dialkylcuprates, addition compounds

Addition of Lithium Dialkylcuprates to cr,/3-Unsaturated Phosphoryl Compounds... 

The addition of lithium dialkylcuprates to a,8-unsaturated compounds is one of the effective and simple methods for carbon -carbon bond formation (2). In recent years significant synthetic importance has been gained by the reaction sequence in which orga-nocopper adducts are utilized as nucleophiles (2, Z, ). This sequence enables geminal functionalization of activated olefins particularly useful for the synthesis of natural products. 

Selenium-stabilized carbanions can be also generated by 1,4-addition of nucleophilic reagents to a-selanyl a,[3-unsaturated carbonyl compounds. The conjugate addition of trialkylsilyllithium compounds to 133, followed by reaction with allyl iodide, afforded the addition products 134 with good m-stereoselectivity (R = Me dr 86 14 R = Ph dr 94 6) (Scheme 34).214 The addition of lithium dialkylcuprates to 2-phenylselanylcycloalk-2-enones has also been used for the synthesis of natural products.215,216... 

In a similar fashion, diethyl cyclopropane-1,1-dicarboxylate (4) reacted with lithium dialkyl-cuprate to give the corresponding malonates S in high yields. Byproducts could be formed by the attack of the organometallic reagent at the carbonyl function. With diethyl 2-vinyl-cyclopropane-1,1-dicarboxylate (6), a preference for the 1,7-addition of the dialkylcuprate was found. Similar observations were made with 1-acetyl- (9,R = Me) and 1-benzoyl-2-vinylcyclopropane (9, R = Ph) when reacted with various dialkyl- and diphenylcuprates and with a vinylcyclopropanedicarboxylate fragment incorporated into a polycyclic system to yield compound 11. ... 

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