Ketones with aldehydes

When the a,P-unsaturated ketone is hydrogenated to the alcohol, a product with an intense sandalwood odor is produced (162). Many other examples of useful products have been made by condensation of campholenic aldehyde with ketones such as cyclopentanone and cyclohexanone. 

An alternative strategy to access cross-benzoin products is to tether the two reactive parmers. This approach has the disadvantages inherent to intramolecular reactions, but it provides access to products produced by the coupling of aldehydes with ketones, hi... 

Scheme 2.2. Mixed Condensation of Aromatic Aldehydes with Ketones... 

Scheme 9.19. Proline-catalyzed three-component reaction of aldehydes with ketones and Meldrum s acid.

A direct aldol-Tishchenko reaction of aromatic aldehydes with ketones proceeds with stereocontrol of up to five contiguous centres in a chain, using titanium(IV) r-butoxide and cinchona alkaloids.146 A tricyclic transition state is proposed to explain the high (g) degree of stereoselection. 

Polymers containing the 4-vinylpyridine moiety complexed to cobalt(II) acetate have been used to catalyze the condensation of aldehydes with ketones. High yields of a,/ -unsaturated ketones are formed at 80 °C in DMF.250... 

Schiff bases commonly employ polyamines as reagents, the donor nature of the ligands depending both on the type of aldehyde or ketone used and the nature of primary amine or diamine. Scheme 1 illustrates some ways of obtaining Schiff bases of different denticities via 1 1 reactions of aldehydes with ketones to yield mixed N, O, S, and Se donor sets. Condensation of aldehydes and ketones with a-amino acids is also known. Where two moles of a carbonyl compounds and one mole of diamine are reacted, more elaborate Schiff bases with higher denticity result, also exemplified in Scheme 1. 

S-Hydfoxy ketones obtained by the condensation of ketones or by the crossed condensation of aldehydes with ketones are important sources of olefinic ketones. Dehydration is effected by warming the ketols with oxalic acid, dilute sulfuric acid, hydrobromic acid, phosphoric acid, or a trace of iodine. A typical example is the dehydration of diacetone alcohol obtained from the self-condensation of acetone. The product is an equilibrium mixture of the conjugated and unconjugated isomers, (CHj)jC=CHCOCHj and CHj=C(CHj)CHjCOCHj, in a ratio of 91 to 9, respectively. ... 

Ryan, H. Devine, A. XII On the Condensation of Aldehydes with Ketones Proceedings of the Royal Irish Academy (1916) 32B 208-216... 

Rates for competing processes such as self-condensation of cyclohexanone and Cannizzaro or Tishchenko reactions of benzaldehyde are negligible compared with the Claisen-Schmidt condensation of aldehyde with ketone. 

Oxoalkyl)benzothiazolines (prepared by the reaction of 3-methyl-2-phenylbenzothiazolim fluorosulfate with lithium enolates of ketones) act as enolate-transferring reagents in Lewis acid promoted cross aldol reactions of aldehydes with ketones (Equation (96)) <90BCJ497>. 

Cyclocondensation of o-aminoaryl ketones, or aldehydes with ketones possessing an a-CH2 group Friedlander synthesis) involves formation of o-aminocinnamoyl systems, e.g. 65 [99] ... 

Strongly solvent-dependent and is unsuccessful in THF, chloroform, benzene, and Other cyclizations utilize the Pd-catalyzed intramolecular aldol reaction of aldehydes with ketone enolates. The reaction is initiated by the oxidative addition of allylic esters to Pd(0) (Scheme 38)/ Chiral ferrocenyl phosphines with polar... 

In 2010, the Enders group reported asymmetric cross-benzoin reactions of aldehydes with ketones by using a novel chiral triazolium NHC catalyst precursor with a sterically demanding silyl protecting group. Under the optimized conditions, several heteroaromatic aldehydes reacted smoothly with aromatic trifluoroketones (2.0 equiv.) providing cross-benzoin products in up to 96% yield and 85% ee, and the enantioselectivity was improved to 99% ee by further crystallization. Through direct observation of the reaction by NMR and racemization experiments, the authors showed that the product is formed under kinetic control (Scheme 7.6). 

The aldol reaction of aldehydes with ketones where an aldehyde acts as a donor was developed by Jprgensen and co-workers [125], In the presence of L-proline,... 

A simple amino sulfonamide (54) - easily prepared from L-phenylalanine -catalyses direct aldols of aldehydes with ketones in brine, giving anf/-aldols in up to 97% ee. ... 

The most widely used catalysts for acid-catalyzed aldol condensations are the molecular sieve zeolites, for example, crystalline aluminosilicates of group I and II elements, in which the latter have been replaced by protons. The surface protons confer Br0nsted acidity. Among the acidic zeolites we can mention HZSM-5 (pentasil zeolite), HY (faujasite), or HM (mordenite). Recently, polystyrene-supported sulfonic acids such as those of the macroreticular strongly acidic cation-exchange resins (59) and acid-base functionalized mesoporous materials such as amine and sulfonic acid-containing SBA-15 (60) have been shown to promote the acid-catalyzed aldol condensation of aldehydes with ketones at low temperatures. 

Formyl-pinane can be isolated from the aldehyde mixture as pure compound in moderate yield by distillation with a column of 20 trays [70a]. In turn, the aldehyde was converted into the primary amine by reductive amination with ammonia. The chiral amine has been utilized, for example, for the optical resolution of racemic pantolactone. Alternatively, aldol condensation of the formed aldehydes with ketones and subsequent hydrogenation give alcohols that might have a broad scope of potential applications in perfumes, soaps, and shampoos [73]. 

Mixed condensation of aromatic aldehydes with ketones... 

By replacing the aldehydes with ketones, quinoxaline derivatives could be synthesized by using PEG 400 [97]. The reaction takes place in tiie presence of KOH at 60°C for 60h (Scheme 66). 

Figure 21 Aldol reaction of aldehydes with ketones catalyzed by [Zn2(HC00)(Fei (H20)-TCPP)]...

A fluorous chiral organocatalyst (18) promotes the formation of the anti-Mol product (with up to 96% ee) on reaction between aromatic aldehydes with ketones in brine. The enantioselectivity achieved on promotion of aldol and Mannich reactions by another di-diamine-based catalyst (19) can be reversed by the addition of an achiral acid and is to be the subject of further mechanistic investigation. ... 

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