threecomponent

Threecomponent, often written as three-component in literature, is a term used in chemistry to describe reactions in which three distinct starting materials react in a single reaction vessel (one-pot) to form a single product. It is a subset of multicomponent reactions (MCRs) and emphasizes the involvement of three components rather than two or more than three. Three-component reactions are valued for atom economy and convergence, enabling rapid construction of complex molecules from simple building blocks.

Common examples include the Biginelli reaction, which combines an aldehyde, a β-keto ester, and urea or thiourea to form dihydropyrimidinones; the Hantzsch dihydropyridine synthesis, which uses an aldehyde, a β-keto ester, and ammonia or ammonium acetate to yield dihydropyridines; and the Passerini three-component reaction, which involves an aldehyde or ketone, an isocyanide, and a carboxylic acid to produce α-acyloxyamide products. In each case, the three inputs come together in one pot to form a product with often high atom efficiency and broad potential for structural diversification.

Applications of threecomponent reactions span medicinal chemistry, natural product synthesis, and materials science, where rapid library generation and streamlined purification are advantageous. They are commonly viewed within the broader framework of green chemistry principles, reducing steps and purification issues compared to conventional multi-step sequences.

Historically, multicomponent chemistry expanded in the mid-20th century and diversified into many named reactions; threecomponent is used descriptively to categorize reactions that employ three inputs. The term does not denote a single universal protocol but a broad class sharing the three-component concept. See also multicomponent reaction, Biginelli reaction, Hantzsch reaction, Passerini reaction.