A mechanism for the following reaction of an α,β- unsaturated ester is to be proposed. Concept introduction: The steps involved in the conversion are i) Nucleophilic attack of the amine on the carbon on the α,β- unsaturated ester ii) Proton abstraction from the acid iii) A proton exchange from N to O iv) Another nucleophilic attack of N on the carbonyl carbon v)Another proton exchange from N to O vi) Loss of methanol and a proton. To propose: A mechanism for the reaction of an α,β- unsaturated ester with methylamine.

Question

When an α-hydroxy amide is treated with Br2 in aqueous NaOH under Hofmann rearrangement conditions, loss of CO2 occurs and a chain-shortened aldehyde is formed. The mechanism involves the following steps: Base abstracts an acidic amide proton, yielding amide anion 1; The amide anion reacts with bromine in an α-substitution reaction to give N-bromoamide 2. Abstraction of the remaining amide proton by base gives a resonance-stabilized bromoamide anion 3; Rearrangement occurs to yield isocyanate 4; Water adds to the isocyanate to yield carbamic acid 5; Elimination of CO2 yields carbinolamine 6; Following proton transfer, expulsion of ammonia yields the final product aldehyde. Write out the mechanism and then draw the structures of bromoamide anion 3 and amide anion 1.

Answer 1

Question

Chapter 19.SE, Problem 51MP

Interpretation Introduction

Interpretation:

A mechanism for the following reaction of an α,β- unsaturated ester is to be proposed.

Concept introduction:

The steps involved in the conversion are i) Nucleophilic attack of the amine on the carbon on the α,β- unsaturated ester ii) Proton abstraction from the acid iii) A proton exchange from N to O iv) Another nucleophilic attack of N on the carbonyl carbon v)Another proton exchange from N to O vi) Loss of methanol and a proton.

To propose:

A mechanism for the reaction of an α,β- unsaturated ester with methylamine.

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