Paserinni y petasis

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Multicomponent Reactions
Multicomponent Reactions (MCRs) are convergent reactions, in which three or more starting materials react to form a product, where basically all or most of the atomscontribute to the newly formed product. In an MCR, a product is assembled according to a cascade of elementary chemical reactions. Thus, there is a network of reaction equilibria, which all finally flow intoan irreversible step yielding the product. The challenge is to conduct an MCR in such a way that the network of pre-equilibrated reactions channel into the main product and do not yield sideproducts. The result is clearly dependent on the reaction conditions: solvent, temperature, catalyst, concentration, the kind of starting materials and functional groups. Such considerations are of particularimportance in connection with the design and discovery of novel MCRs. (A. Dömling, Org. Chem. Highlights 2004, April 5. Link)
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A. Dömling, Org. Chem. Highlights 2004, April 5.
[pic]Multicomponent Reactions with Carbonyl Compounds
Some of the first multicomponent reactions to be reported function through derivatization of carbonyl compounds into more reactive intermediates, which canreact further with a nucleophile. One example is the Mannich Reaction:
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Mannich Reaction
Obviously, this reaction only proceeds if one carbonyl compound reacts faster with the amine to give animine, and the other carbonyl compound plays the role of a nucleophile. In cases where both carbonyl compounds can react as the nucleophile or lead to imines with the same reaction rate, preforming theintermediates is an alternative, giving rise to a standard multistep synthesis.
Carbonyl compounds played a crucial role in the early discovery of multicomponent reactions, as displayed by a numberof name reactions:
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Biginelli Reaction
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Bucherer-Bergs Reaction
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Gewald Reaction
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Hantzsch Dihydropyridine (Pyridine) Synthesis
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Kabachnik-Fields Reaction
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