Cyclohexenones reaction with lithium dimethylcuprate

Cyclohexenones and Related Derivatives. House and Wilkins have now demonstrated that addition of lithium dimethylcuprate to 3-methylcyclohex-3-enone in 1 1 molar equivalents results in a solution of the lithium enolate and a precipitate of (MeCu). Even when soluble cuprous species occur, there is no evidence to suggest that reaction with lithium enolates to give copper(i) enolates occurs. In a 1,4-addition reaction phenylithio[(a-diethoxymethyl)vinyl] cuprate with cyclohexenone at 233 K in Et20 gave ultimately 88% of the 3-allylcyclohexanone (38) (a-diethoxymethyl)-vinylcopper gave the 1,2-addition product. 

The conjugate addition of enolate anions to activated 3-trimethylsilyl-3-buten-2-one helped solve another long-standing problem in organic synthesis by permitting the annulation reaction to be carried out in aprotic solvents under conditions where enolate equilibration is avoided. The annulation of thermodynamically unstable lithium enolates with MVK, where equilibration to the more stable enolate occurs prior to Michael addition, often yields a mixture of stractmal isomers. For exan le, Boeckman successfully employed 3-trimethylsilyl-3-buten-2-one in a Robinson annulation sequence (eq 2). Thus treatment of cyclohexenone with lithium dimethylcuprate in diethyl ether and then with 3-trimethylsilyl-3-buten-2-one gives the desired Michael adduct, which is converted into the functionalized octalone in 52% overall yield. ... 

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