Which double bond is more electrophilic : carbon-carbon or carbon-oxygen?

Question

Question

Attempt

It seems to me that the carbon-oxygen bond would be more electrophilic due to the higher electronegativity of oxygen. Hence I believe $\ce{CH3-}$ should attack the carbonyl site. But this doesn't seem to be the case.

Is it because that the intermediate carbanion can undergo resonance with oxygen, had $\ce{CH3-}$ attacked carbon- carbon double bond?

What can be a valid reason?

Answer 1

step-1: cleavage of C=O bond:

• the C=O bond undergoes heterolytic cleavage to give positive charge on carbon and negative charge on oxygen just like almost all other organometallic reagents react with a ketone, for example a grignard reagent (not exactly, but similar to it).

step-2:(the real step which caused deviation from your answer)-resonance of intermediate:

• the positive charge on the carbon of the erstwhile C=O group now undergoes resonance with the double bond at the allylic position to give positive charge at carbon no. 3 instead of carbon no. 1

• in this sort of reaction is 1,4 addition occurs instead of 1,2 addition. For more information, you can visit this link: https://chem.libretexts.org/Bookshelves/Ancillary_Materials/Reference/Organic_Chemistry_Glossary/1%2C4-Addition

step 3:(as usual):-attack of CH3 group:

• now on as usual, the CH3 group from our organo copper reagent ( called as gilmann reagent, used in Corey-house synthesis), just like a grignard reagent, attacks the new carbocation formed at carbon no.3 and the water molecule in the second step donates it's proton to the remnant oxygen of our old C=O group and it becomes an enol. tautomerisation takes place and we bet 3-methyl cyclohexanone as a result.