A multi-component reaction (or MCR), sometimes referred to as a "Multi-component Assembly Process" (or MCAP), is a
chemical reaction
A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...
where three or more
compounds
react to form a single product. By definition, multicomponent reactions are those reactions whereby more than two reactants combine in a sequential manner to give highly selective products that retain majority of the atoms of the starting material.
History and types of multicomponent reactions
Multicomponent reactions have been known for over 150 years. The first documented multicomponent reaction was the Strecker synthesis of α-amino cyanides in 1850 from which α-amino acids could be derived. A multitude of MCRs exist today, of which the isocyanide based MCRs are the most documented. Other MCRs include free-radical mediated MCRs, MCRs based on organoboron compounds and metal-catalyzed MCRs.
Isocyanide based MCRs are most frequently exploited because the isocyanide is an extraordinary functional group. It is believed to exhibit resonance between its tetravalent and divalent carbon forms. This induces the isocyanide group to undergo both electrophilic and nucleophilic reactions at the CII atom, which then converts to the CIV form in an exothermic reaction. The occurrence of isocyanides in natural products has also made it a useful functional group. The two most important isocyanide-based multicomponent reactions are the Passerini 3-component reaction to produce α-acyloxy carboxamides and the Ugi 4-component reaction, which yields the α-amino carboxamides.
Examples of three component reactions:
*
Alkyne trimerisation
*
Biginelli reaction
*
Bucherer–Bergs reaction
*
Gewald reaction
*
Grieco three-component coupling
*
Hantzsch pyridine synthesis
*
Kabachnik–Fields reaction
*
Mannich reaction
*
Passerini reaction
*
Pauson–Khand reaction
*
Petasis reaction
*
Strecker amino acid synthesis
*
Ugi reaction
*
Asinger reaction
*
A3 coupling reaction
The exact nature of this type of reaction is often difficult to assess, in
collision theory
Collision theory is a principle of chemistry used to predict the rates of chemical reactions. It states that when suitable particles of the Reagent, reactant hit each other with the correct orientation, only a certain amount of collisions result ...
a simultaneous interaction of 3 or more different molecules is less likely resulting in a low
reaction rate. These reactions are more likely to involve a series of bimolecular reactions.
New MCR's are found by building a
chemical library from
combinatorial chemistry or by combining existing MCR's. For example, a 7-component MCR results from combining the
Ugi reaction with the
Asinger reaction. MCR's are an important tool in new drug discovery. MCR's can often be extended into combinatorial, solid phase or flow syntheses for developing new lead structures of active agents.
[''Multicomponent reactions'' Thomas J. J. Müller (Editor]
Thematic Series
in the Open Access Beilstein Journal of Organic Chemistry
See also
* A
tandem reaction is a consecutive series of
intramolecular organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, mechanistic organ ...
s.
References
{{Reflist
External links
Multicomponent reactionsPresentation on Multicomponent Reactions
Chemical kinetics
Chemical synthesis