Aldehydes are compounds with a terminal carbonyl (HC=O) moiety, and are either unsaturated, that is, containing one or more carbon–carbon double bonds, or saturated. Aldehydes (R-CHO) are useful building blocks due to their ability to easily react with many nucleophiles. Because of their high chemical reactivity, aldehydes are important intermediates for the manufacture of solvents, resins, dyes, plasticizers, and pharmaceuticals. AA Blocks offers a wide range of compounds containing the aldehyde functional group for use as building blocks in a variety of synthetic procedures. For example, the asymmetric allylation and crotylation of aldehydes and other carbonyl compounds remains one of the most fundamental reactions for the construction of chiral building blocks. The Stetter reaction (conjugate addition of an aldehyde to an α,β-unsaturated compound) is a superb method for the construction of 1,4-dicarbonyl compounds bearing quaternary stereocenters.