Q.45. - Organic Chemistry

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.

Step-by-Step Solution

Answer

Answer

 

a.

                                           

b.

Step 1: 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

Step 2: 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

Step 3: 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: