Diketene derivatives
(mainly acetoacetic acid derivatives and heterocycle
compounds) have
versatile applications including making agrochemicals, dyes,
pigments, pharmaceuticals including vitamins, and
stabilizers for PVC and polyester. Acetoacetic acid
and its esters contain
active methylene groups which have relatively acidic alpha-protons due to H
atoms adjacent to two carbonyl groups. The reactivity of its methylene group
provide the sequence of reactions of alkylation, hydrolysis of the esters and
decarboxylation resulting in substituted ketones. The
methylene group can be reacted to form amino-carbonyl compounds.
Acetoacetates
are important aliphatic parts adjoining azo dyes and pigments. Acetoacetic acid is unstable and
decompose to acetone and carbon dioxide at room temperature.
Ethyl
acetoacetate has
a reactive hydrogen atom on the carbon alpha to
both carbonyl groups. It undergoes Knoevenagel condensation reaction as a reactant
to forms a large class of target products including
amino acids, drugs (analgesics, antibiotics, antimalarial
agents, antipyrene and aminopyrene), and vitamin B1.
It is also involved in the
production of colorants, lacquers,
perfumes, and plastics. Alone, it is used as a flavoring agent and a solvent.
Knoevenagel condensation is a nucleophilic addition of a
reactive
hydrogen atom at 1,3-diketone compounds to a carbonyl
group, followed by an dehydration reaction. 1,3-Diketone compounds (beta-ketones)
include malonic
acid, diethyl malonate,
Meldrum's acid,
and acetoacetic acid derivatives. |