Reactions used in DCvC must generate thermodynamically stable products to overcome the entropic cost of self-assembly. The reactions must form covalent linkages between building blocks. Finally, all possible intermediates must be reversible, and the reaction ideally proceeds under conditions that are tolerant of functional groups elsewhere in the molecule.
Reactions that can be used in DCvC are diverse and can be placed into two general categories. Exchange reactions involve the substitution of one reaction partner in an intermolecular reaction for another with an identical type of bonding. Some examples of this are shown in schemes 5 and 8, in an ester exchange, and disulfide exchange reactions. The second type, formation reactions, rely on the formation of new covalent bonds. Some examples include Diels–Alder and aldol reactions. In some cases, a reaction can pertain to both categories. For example, Schiff base formation can be categorized as a forming new covalent bonds between a carbonyl and primary amine. However, in the presence of two different amines the reaction becomes an exchange reaction where the two imine derivatives compete in equilibrium.
Exchange and formation reactions can be further broken down into three categories:
# Bonding between carbon–carbon
# Bonding between carbon–heteroatom
# Bonding between heteroatom–heteroatom