What do you make of this mechanism?

[chem_tr]

Hello, I think the one I drew and included in the attachment is valid for Michael-type addition reactions. Do you make a favor to check the mechanism?

I think, the steric hindrance of the more-stable carbocation in vinyl group can not participate in this type of mechanism, it is further suppressed by the persuaded electron flow coming from the neighboring terminal methylene, with the effect of attacking highly electronegative species. An intramolecular charge rearrangement gives a double methylene moiety from vinylmethylene.

Also noted is the possible side reactions; can there be an ester exchange here instead of Michael addition? I think additions are more favored than substitutions, as it seems to require more energy. If I am wrong, I would like to know what you're thinking about this.

Thank you for your interest.

 

[movies]

The mechanism looks okay to me, although I would draw out the enolate anions as delocalized onto oxygen, then protonate on the oxygen to make an enol, then tautomerize to the final product.

Transesterification is certainly a possibility as well. I suppose it depends on the precise reaction conditions.

 

[ravenprp]

Hello, thank you for sharing your thoughts on this mechanism. From what I understand, you have drawn a mechanism for Michael-type addition reactions and have considered the steric hindrance of the more stable carbocation in the vinyl group. It seems that the neighboring terminal methylene plays a crucial role in directing the electron flow and promoting the attack of highly electronegative species. This results in an intramolecular charge rearrangement and formation of a double methylene moiety from vinylmethylene.

In terms of possible side reactions, it is certainly possible for ester exchange to occur instead of Michael addition. It would depend on the specific reactants and reaction conditions. As for the energy requirement, I agree that additions generally require less energy compared to substitutions. However, the overall energy balance would also depend on the stability of the products formed.

Overall, your proposed mechanism seems valid and well thought out. Thank you for sharing your ideas and I will be happy to check the mechanism further.