91Ó°ÊÓ

As per the given reaction product is formed by the two carbonyl condensation and that occurs as:

As the reagent OH^-is given which abstracts the acid proton the proton next to carbonyl carbon and which leads to an attack on the carbonyl carbon of another compound and converts carbonyl to hydroxyl with its removal and formation of Penta ring takes place.

Mechanism followed as:

1. Abstraction of an acidic proton from the left side of carbonyl of diphenyl acetone

2. Attack of another carbonyl

3. Formation of the hydroxyl group

4. Removal of hydroxyl group followed by elimination of a proton and double bond take place

5. The Same process is repeated on the right side acidic proton of the diphenyl acetone

6. Penta Cyclic ring formation occur

7. Desired product formed