Diisobutylaluminum hydride (DIBAL-H) is an organoaluminum reagent typically used for the reduction esters or nitriles to aldehydes.
In the second step intramolecular aldol condensation reaction takes place. Cyclization occurs if the α carbon atom and the second carbonyl carbon atom can bond to form a five- or six-membered ring.
The Clemmensen reduction is a reaction that is used to reduce aldehydes or ketones to alkanes using hydrochloric acid and zinc amalgam. In the same condition, alcohol converts to alkenes.

