Question

provide a detailed curved-arrow mechanism to account for the transformation below and explain why the only products formed at high and low temperatures are the ones shown.

Provide a detailed curved-arrow mechanism to account for the transformation below and explain why the only products formed at high and low temperatures are the ones shown. (Show all resonance contributors for all intermediates): ya +En. octh

Answer 1

From the mechanism shown below , we can understand that at low or high temperatures , the only intermediate that forms is the resonance stabilised carbocation shown.

The extra favor for 1,4 addition even at low temperatures comes from the fact that the the methoxy group of enol ether always facilitats the stabilization leading to 1,4 addition only. { the positive charge at the carbon attached to OCH3 is minimum due to +M of O}

о- анз о — ина 0-сеъ Resonance stabilized - en. би,