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The Japp–Maitland condensation is an organic reaction and a type of Aldol reaction and a tandem reaction.In a reaction between the ketone 2-pentanone and the aldehyde benzaldehyde catalyzed by base the bis Aldol adduct is formed first.
An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties (of aldehydes or ketones) react to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), and this is then followed by dehydration to give a conjugated enone. The overall reaction equation is as follows (where the Rs can be H)
In its simplest implementation, base induces conversion of an aldehyde or a ketone to the aldol product. One example involves the aldol condensation of propionaldehyde: 2 CH 3 CH 2 CHO → CH 3 CH 2 CH(OH)CH(CH 3)CHO. Featuring the RCH(OH)CHR'C(O)R" grouping, the product is an aldol. In this case . Such reactions are called aldol aldol ...
This reaction is an important approach to the formation of carbon-carbon bonds in organic molecules containing ring systems. As an example, under strong basic conditions (e.g. sodium hydroxide), hexane-2,5-dione (compound A in Figure 1) can cyclize via intramolecular aldol reaction to form the 3-methylcyclopent-2-en-1-one (compound B).
It is a modification of the aldol condensation. [1] [2] A Knoevenagel condensation is a nucleophilic addition of an active hydrogen compound to a carbonyl group followed by a dehydration reaction in which a molecule of water is eliminated (hence condensation). The product is often an α,β-unsaturated ketone (a conjugated enone).
Chiral auxiliaries are incorporated into synthetic routes to control the absolute configuration of stereogenic centers. David A. Evans' synthesis of the macrolide cytovaricin, considered a classic, utilizes oxazolidinone chiral auxiliaries for one asymmetric alkylation reaction and four asymmetric aldol reactions, setting the absolute stereochemistry of nine stereocenters.
It can also be prepared by combining ethylene, CO, and H 2. [4] When the reaction is catalyzed by dicobalt octacarbonyl, water can be used as a source of hydrogen.A proposed intermediate is the ethylene-propionyl species [CH 3 C(O)Co(CO) 3 (ethylene)] which undergoes a migratory insertion to form [CH 3 COCH 2 CH 2 Co(CO) 3].
A classic example for favoring the keto form can be seen in the equilibrium between vinyl alcohol and acetaldehyde (K = [enol]/[keto] ≈ 3 × 10 −7). In 1,3-diketones, such as acetylacetone (2,4-pentanedione), the enol form is favored. The acid-catalyzed conversion of an enol to the keto form proceeds by proton transfer from O to carbon.