Reaction type
Aldehydes, ketones or carboxylic acid derivatives etc. Carbonyl compound stay carbonyl Forming new Carbon carbon bond To combine two molecules. These reactions usually occur in acid or alkali Catalysis Next. A carbonyl compound is formed in the reaction Enol Or enol anion Later attack another carbonyl carbon atom To form a new carbon carbon bond. The simplest example is acetaldehyde Of Aldol condensation Reaction, product 3-hydroxybutyraldehyde It is possible to further water loss And become 2-Butenoaldehyde ， Acid catalysis advantageous to dehydration reaction For. The reaction of 2-butenal from acetaldehyde is carbonyl and methylene It can be seen from the examples of condensation that such condensation starts in the form of aldol condensation, and then loses water to obtain the product of carbon carbon double bond. Claisen condensation reaction
Esters containing α - active hydrogen Sodium alkoxide 、 Sodium triphenylmethyl Under the action of alkaline reagents, condensation reaction occurs to form β -- Keto acid Ester compounds , called claisen condensation The reaction can be carried out between different esters, which is called cross ester condensation; This reaction can also be used for binary Carboxylate Of Intramolecular cyclization At this time, the reaction is also called Dickman reaction. For example, ethyl acetate stay Sodium ethoxide Generated under action Ethyl acetoacetate 。 Perkin condensation reaction
Aromatic aldehyde And Aliphatic group Carboxyl Acid anhydride In the corresponding Sodium carboxylate Under the action, cinnamic acid type compounds are formed.
Perkin condensation reaction Aromatic aldehydes in Potassium cyanide Under the action, two molecules condense to form benzoin compounds. Stobe condensation reaction
Aldehydes or ketones and Succinic acid Esters generate 2 under the action of strong base- Alkylene Succinic acid derivatives.
Stobe condensation reaction Coupling condensation reaction
Carboxylate and sodium generation Bimolecular reduction , to form an even in compound. If appropriate chain dicarboxylic acid ester is used as raw material, through this reaction, intermolecular coupling condensation can occur, and the middle ring compound can be prepared. Mannich reaction
Aldehydes or ketones and formaldehyde And secondary amine or primary amine under weak acidic conditions Ammomethylation Reaction. Using this reaction, we can synthesize some complex, natural only N-Contained Organic Compounds 。 For example, use mole Of Butyraldehyde 、 3-Pentanone Diacid and Methylamine Of dilute solution Condensation at 35 ℃, pH=5 Tropinone 。
Mannich reaction Aldehydes or ketones and Wittig reagent Condensation occurs, which is synthesis olefin Important methods. Aryl halides stay copper powder (or Cuprous chloride 、 Cupric oxide 、 copper sulphate 、 Cupric acetate ) react with aromatic amines in the presence of to generate higher aromatic amines. When halogenated aromatic hydrocarbon has Electron withdrawing group And aromatic amine Electron donor group Is conducive to the reaction. Other than aromatic amine Nucleophile Such as phenol Thiophenol Can also participate in this reaction. This method can be used to prepare higher aromatic amines from aromatic amines. Enol anion or others Negative carbonion (e.g. CN - ）Attack in alkaline conditions α,β -Unsaturated carbonyl compounds or α , β -Isoelectrophilic unsaturated nitrile Conjugate system Negative carbon ions attack β -Carbon atoms occur simultaneously 1,4-addition 。 Such reactions are called Michael addition reaction 。 When the product obtained from the Mailke reaction is 1,5-diketone, it can undergo intramolecular aldol condensation to form a cyclohexene ketone ring system, which is called Robinson ring increasing reaction. Darzen condensation reaction
Aldehydes or ketones and α -Halogenated carboxylic acid ester loses Halogen ion And get α , β -Epoxy carboxylate. It is easy to lose its carboxyl after hydrolysis to form higher grade aldehydes or ketones. 
