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Piperidine is widely used to convert ketones to enamines. [23] Enamines derived from piperidine are substrates in the Stork enamine alkylation reaction. [24] Upon treatment with calcium hypochlorite, piperidine converts to N-chloropiperidine, a chloramine with the formula C 5 H 10 NCl.
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). General Knoevenagel layout
The Dakin oxidation (or Dakin reaction) is an organic redox reaction in which an ortho- or para-hydroxylated phenyl aldehyde (2-hydroxybenzaldehyde or 4-hydroxybenzaldehyde) or ketone reacts with hydrogen peroxide (H 2 O 2) in base to form a benzenediol and a carboxylate. Overall, the carbonyl group is oxidised, whereas the H 2 O 2 is reduced.
Schiff bases can be obtained by reacting amines with ketones or aldehydes. [189] These reactions are a common method of producing C=N bonds. [190] In the biosynthesis of alkaloids, such reactions may take place within a molecule, [188] such as in the synthesis of piperidine: [41]
Piperidine, a cyclic six-membered amine that results from hydrolysis of piperine; Piperic acid, the carboxylic acid also derived from hydrolysis of piperine; Capsaicin, the active piquant chemical in chili peppers; Allyl isothiocyanate, the active piquant chemical in mustard, radishes, horseradish, and wasabi
The reaction of pyridine with bromomethyl ketones gives the related pyridinium salt, wherein the methylene group is highly acidic. This species undergoes a Michael-like addition to α,β-unsaturated carbonyls in the presence of ammonium acetate to undergo ring closure and formation of the targeted substituted pyridine as well as pyridinium bromide.
Piperonal can be prepared by the oxidative cleavage of isosafrole or by using a multistep sequence from catechol or 1,2-methylenedioxybenzene.Synthesis from the latter chemical is accomplished through a condensation reaction with glyoxylic acid followed by cleaving the resulting α-hydroxy acid with an oxidizing agent.
Cyclic and acyclic dienes generally give cyclobutanones, rather than Diels-Alder adducts. In reactions of cyclic dienes, the larger ketene substituent is placed in the endo position. [11] Fulvenes typically react in the ring, leaving the double bond intact. [12] (6) Ketenes undergo [2+2] cycloaddition with ketones and aldehydes to give β-lactones.