Popular since the early 1900s, the 1,4-addition of Michael donors to activated π-systems (called Michael acceptors) to form new C-C bonds is known as the Michael addition or reaction. With the help of a base, the donor is converted to an enolate ion, which attacks the Michael acceptor. When a full equivalent of base is used, the (anion) product can further react with various electrophiles. Other processes such as 1,2-addition or self-condensation may compete with the desired 1,4-addtion, but the use of additives and the careful selection of the reaction medium can limit these undesired reactions.