Question

Question: Draw the product of each Robinson annulation from the given starting materials using $\mathit{O}\mathit{H}$in ${\mathit{H}}_{\mathbf{2}}\mathit{O}$solution.

Short answer

Answer

a.

b.

Step-by-step solution

Robinson annulation

Robinson annulation is the combination of aldol condensation and Michael reaction, involving an $\mathit{\alpha }\mathbf{,}\mathit{\beta }$-unsaturated ketone and a carbonyl compound that forms an enolate. The general reaction is given below:

Robinson annulation

Mechanism of Robinson annulation

The initial steps resemble the Michael addition, as shown below:

Mechanism of Robinson annulation similar to that of Michael addition

The steps after this resemble that of Aldol condensation followed by dehydration:

Mechanism of Robinson annulation similar to that of Aldol condensation

Determination of product

The starting materials are redrawn and based on the mechanism of Robinson annulation, the products of the given reactions are shown below: