Condensation of carbonyl compounds

Schiff bases, also known as imines, ate formed by the condensation of carbonyl compounds with ammonia or primary amines. Hydrogenation of the resulting Schiff bases forms amines, such as benzylamine and dibenzylamine. 

Triflates of titanium and tin are effective catalysts for various condensations of carbonyl compounds [I2I, 122, 123, 124, 125] Claisen and Dieckmann type condensations between ester functions proceed under mild conditions in the presence of dichlorobis(trifluoromethanesulfonyloxy)titaiiiuin(rV) and a tertiary amine (equations 59 and 60) These highly regio- and stereoselective condensations were used successfully m the synthesis of carbohydrates [122]... 

The most widely employed methods for the synthesis of nitrones are the condensation of carbonyl compounds with A-hydroxylamines5 and the oxidation of A+V-di substituted hydroxylamines.5 9 Practical and reliable methods for the oxidation of more easily available secondary amines have become available only recently.10 11 12 13. These include reactions with stoichiometric oxidants not readily available, such as dimethyldioxirane10 or A-phenylsulfonyl-C-phenyloxaziridine,11 and oxidations with hydrogen peroxide catalyzed by Na2W044 12 or Se02.13 All these methods suffer from limitations in scope and substrate tolerance. For example, oxidations with dimethyldioxirane seem to be limited to arylmethanamines and the above mentioned catalytic oxidations have been reported (and we have experienced as well) to give... 

The rate of the base-catalysed condensation of carbonyl compounds with alkyl groups activated by Jt-deficient aromatic systems is enhanced by the addition of quaternary ammonium salts. For example, 2-methylbenzoxazole, 2-methylbenzo-thiazole and 4-nitrotoluene react with a range of substituted benzaldehydes to produce the corresponding 2-styryl derivatives (62-80%) at room temperature over 1 -2 hours [61, 62]. The intermediate alcohol can also be isolated after a short reaction time. 

Lewis acid-catalyzed inter- or intramolecular condensation of carbonyl compounds with strained cyclic peroxides represents one of the most general and useful methods... 

Type and geometry of substrate coordiation plays a key role in the final stereochemistry of the product [245,246]. Organolanthanide catalyzed condensation of carbonyl compounds with silylenolethers, known as the Mukaiyama addition reaction, is assumed to contain a 6-membered transition state with Ln-O linkages [247]. Formation of a 6-membered organolanthanide aldolate moiety was structurally proven in the reaction of Cpf LnR with ketones (Sect. 6.2.3) [248]. 

Tab. 13.7 Representative a,/MJnsaturated Carbonyl Compounds Generated by Aldol Condensations of Carbonyl Compounds with Selected Aldehydes (M = Na or K )...

Also, the primary amine moities of polar lipids catalyze the aldol condensation of Cm-Cig aldehydes resulting from plasmalogen hydrolysis, thus forming a,3-unsaturated aldehydes (l2t). Phosphatidyl ethanolamine reacted with propanal and n-hexanal forming phosphatidyl l-(2-hydroxyethyl)-2-ethyl-3,5-dimethyl pyridinium, and phosphatidyl-1-(2-hydroxy ethyl)-2-hexyl-3,5-dipentyl pyridinium, respectively (125). The peridinium ring is formed by the reaction between one mole of amino-N of phosphatidyl ethanolamine and three moles of n-alkanals. The same reaction took place in the synthesis of substituted pyridines by condensation of carbonyl compounds with ammonia (126, 127). 

F, Ramirez, Condensation of Carbonyl Compounds with Phosphitesters, Pure Appl. Chem. 9, 337 (1964). 

Substituted a-benzylacetoacetic esters have usually been prepared by the general method of Leuchs,4 in which ethyl aceto-acetate is alkylated in ethanol solution with benzyl chloride and sodium ethoxide. The present method is based upon Cope s 6 procedure for the condensation of carbonyl compounds with ethyl acetoacetate, followed by catalytic reduction of the condensation product. 

Alpha substitutions and condensations of carbonyl compounds are some of the most common methods for forming carbon-carbon bonds. These types of reactions are common in biochemical pathways, particularly in the biosynthesis and metabolism of carbohydrates and fats. A wide variety of compounds can participate as nucleophiles or electrophiles (or both) in these reactions, and many useful products can be made. We begin our study of these reactions by considering the structure and formation of enols and enolate ions. 

Condensation of carbonyl compounds. This magnesium phenolate catalyzes the self-condensation of linear aliphatie aldehydes. When the reaction is conducted in HMPT, 1,3-diol monoesters (3 and 4) are formed (equation I). When the reaction is conducted in benzene, 2,3-dialkylacrylaldehydes (5) are formed, also in high yield (equation II). Magnesium ions (MgBr and Mg ) are much more effective in these reactions than Li or Na . ... 

Condensation of Carbonyl Compounds with Compounds Containing an Active Methylene Group (Knoevenagel) ... 

Condensation of Carbonyl Compounds with Halogenated Compounds... 

Condensation of Carbonyl Compounds (Acyloin and Benzoin Condensations )... 

Carbonyl Compounds as Nucleophiles and Electrophiles. The Problem of Role Assignment and the Modern Image of the Classical Condensations of Carbonyl Compounds. The Wittig Reaction as a Method for the Controlled Synthesis of Alkenes... 

Utilization of LDA facilitated the elaboration of a unified protocol for controlled condensations of carbonyl compounds. The protocol generally involves two separate steps. Initially, one of the carbonyl components is transformed entirely into the enolate under the action of LDA. Then, the second carbonyl component (or any other electrophilic reagent) is simply added (Scheme 2.25). The separation in the steps of the enolate generation and its subsequent interaction with an electrophile clearly precludes any confusion of the reacting partners roles and provides an opportunity to vary independently the nature of the reacting components within a broad set of reactants. ... 

The Michael addition represents an extremely efficient synthetic method for achieving chain elongation by adding a three (or more) carbon fragment electrophile to a nucleophilic moiety. Notice that the typical Michael electrophiles (e.g. 90) are products of condensation of carbonyl compounds and can be easily formed via the aldol-like condensation, the Wittig reaction (with ylides like 81), the Perkin reaction, or the Mannich reaction (see below). 

Cyclopropylimines are usually generated by reduction of nitriles or condensation of carbonyl compounds with amines. An alternative to this process involves the generation of cyclopropylinunoni-um salts such as (209) at room temperature from cyanohydrin equivalent (208 Scheme 49). ... 

As mentioned above, the quaternarization method using N-silylmethyl-imines [Eq. (2)] offers an even more general and convenient method of azomethine ylide generation than the original N-silylmethylation method shown by Eq. (1). Another advantage is the ready availability of N-silylmethylimines, which are conveniently prepared by the condensation of carbonyl compounds with silylmethylamine or with silylmethyl azide in the presence of triphenylphosphine (84JOC2688). 

Strecker reaction The condensation of carbonyl compounds with amines and nitriles to afford a-amino nitriles. 446... 

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