1. 1,3-diester is less acidic than a 1,3-ketoester, which is less acidic than an 1,3-diketone due to increased electron donation by the -OR group of the ester.
2. Claisen reactions use a stoichiometric amount of base and do not polymerize, unlike aldol reactions that use a catalytic amount of base and can polymerize.
3. Beta-hydroxy ketones can be formed by thiazolium catalysis with aldehydes.
4. Aliphatic heterocycles typically act like normal ethers, amines, and thioethers unless there is a large amount of ring strain.