Aldehydes (R-CHO) are attractive 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 resins, plasticizers, solvents, dyes, and pharmaceuticals. Sigma-Aldrich offers an extensive array 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.