Which are the requirenments for enolizations?

Any Organic compound with:

• an electron- withdrawing functional group
• at least one π bond joined to a saturated carbon atom bearing an Hydrogen (at least)

can form form an enol in the appropriate neutral or acid environment. 

In addition many compounds with the characteristics listes above can also form enolates in basic solution but there are few exceptions as the carboxylic acids (which lose the acidic COOH proton and resist to another deprotonation) and primary and secondary amides essentially for the same reason, the amide NH proton is taken by the base before than the other suitable protons. Moreover amides are the least reactive.

Te see more about enolates here you are the previous post I posted: LINK 

Source: Organic Chemistry by Clayden, Greeves, Warren and Wothers