1.3- diketones reaction with aldehydes

Another highly fluorinated rare earth y9-diketonate, 21 (Ln = Pr, Eu, Ho dppm = di(perfluoro-2-propoxypropionyl)methanate), showed itself to be a delicate reagent, not only for accomplishing high chemoselectivity in Mukaijama aldol reactions with aldehydes and ketene silyl acetals (KSA) [123], for it was attributed with a mode of stereomodulating catalysis in the aldol reaction of alkoxy aldehydes with KSA (eqs. (12) and (13)). 

Cyanoacetamides yield a-cyanoacrylamides (124) stereoselectively upon reaction with aldehydes and nonselectively with ketones under standard Knoevenagel conditions. a-Cyanoacrylamides (124) are also obtained by partial hydrolysis of methylenemalonodinitriles. With 1,3-diketones, e.g. acetyl-acetone, pyridones like (125) are formed upon reaction with cyanoacetamides. Base-catalyzed dimerization of a-cyanoacrylamides (124) yields piperidones. ... 

Acrolein rarely features as the activated olefins in the MBH reaction with aldehydes, clearly because of its propensity to form oligomers or polymers under the basic catalysts employed. However, this hurdle has been surmounted by selection of appropriate reaction conditions. The DABCO-catalyzed addition of acetaldehyde and propionaldehyde with acrolein proceeded in good yields under a low catalyst concentration, perhaps to minimize the polymerization of acrolein. It is also the exclusive path in the attempted addition of 2-pyridinecarboxaldehyde" and a-diketones to acrolein. In addition, successful MBH reactions of acrolein with aldehydes have been reported xmder high pressure, which affected a dramatic acceleration in the rate of MBH reaction." More reactive electrophiles, including halo ketones, fluoro-carbonyls and activated imines,all reacted very rapidly with acrolein. 

The a-proton of an aldehyde or ketone is less acidic as more carbon substituents are added. As more electron-withdrawing groups are added, the a-proton becomes more acidic, so a 1,3-diketone is more acidic than a ketone. The more acidic proton of an unsymmetrical ketone is the one attached to the less substituted carbon atom 8,12,13,14,22,23,28,30, 77,81,86,89,93. Enolate anions react as nucleophiles. They give nucleophilic acyl addition reactions with aldehydes and ketones. The condensation reaction of an aldehyde or ketone enolate with another aldehyde or ketone is called an aldol condensation. Selfcondensation of symmetrical aldehydes or ketones leads to a single product under thermodynamic conditions. Condensation between two different carbonyl compounds gives a mixture of products under thermodynamic conditions, but can give a single product under kinetic control conditions 5, 9, 11, 15, 16, 17, 18,19,20,21,23,29,30,31,32,33,34,40,41,42,43,44,45,46,49,91, 92, 94,102,114,115,123,134. 

Second, functional group selectivity is observed - i.e. reactions with aldehydes proceed at —78 °C whereas those with ketones proceed at elevated temperatures (ca. 0 °C). Chemoselectivity is observed with acceptors having two different kinds of carbonyl function, for example aldehyde and ketone or ester, in the same molecule. Treatment of phenylglyoxal with silyl enol ether 38 at —78 °C affords a-hydroxy-y-diketone 39 (Eq. (20)) [20b]. The reaction of ketoesters 40 other than j5-ketoesters with silyl enol ether 38 gives hydroxyketoesters 41 as sole products (Eq. (21)) [23]. 

Stannous ene-diolates also give high yields of aldol products, but with little diastereoselectivity. The stannous ene-diolates were prepared in situ by reduction of a-diketones with activated metallic tin, in turn prepared by the reduction of stannous chloride with potassium metal. Stannous enolates of bromomethyl ketones show good stereoselectivity in aldol reactions with aldehydes when... 

Symmetrical 1,4-diketones (249) can be prepared by the reaction of phenyl vinyl sulfones (53) or divinyl sulfone with aldehydes in the presence of 3-benzyl-5-(2-hydroxymethyl)-4-methylthiazolium chloride as a catalyst (equations 148 and 149)142. 

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

A cross-coupling reaction of aldehydes with a-diketones proceeded in the presence of water to give the corresponding adducts in moderate to good yield. It is possible to use the substrates such as phenyl-glyoxal monohydrate, aqueous methylglyoxal, formalin, and aqueous a-chloroacetaldehyde for this reaction.330... 

E)- or (Z)-y-alkoxyallylstannanes, Bu3SnCH2CH=CHOR, undergo a light-promoted reaction with various classes of carbonyl compounds (aldehydes, ketones, O -diketones) to give homoallylic alcohols with retention of double-bond geometry. 

It was reported [59] that temperature in combination with the choice of catalyst is, indeed, the main factor in controlling the direction of this MCR. Under ambient and neutral conditions, the reaction between 5-amino-3-phenylpyrazole, cyclic diketones, and aromatic aldehydes yielded Biginelh-type dihydropyrimidines 54 (Scheme 24). Increase in the reaction temperature with simultaneous addition of triethylamine allowed the reaction to proceed along the thermodynamically controlled pathway with formation of dihydropyrazolopyridines 53. 

Interesting reagents for such MCRs from the viewpoint of selectivity tuning are 5-aminopyrazoles containing carboxamide substituent. In the first article concerning the behavior of these aminozoles in the reactions with cyclic 1,3-diketone and aldehydes, it was found that only one direction of the treatment leads to tricyclic Biginelli-like heterocycles 61 (Scheme 30) [96]. 

Although yields and diastereoselectivities are moderate, a cross-pinacol coupling reaction between a 1,2-diketone and an aldehyde is accomplished with Sml2 in the presence of HMPA. ... 

Monocyanohydrins of P-diketones.3 In the presence of TiCl4, acetyl cyanide reacts with enol silyl ethers of ketones at - 78° to afford monocyanohydrins of diketoncs in excellent yield. The corresponding reaction with enol silyl ethers aldehydes proceeds in only about 35% yield. A low temperature is essential for this reaction. A similar reaction is possible with allyltrimethylsilane. 

Hydroxy alky l-l, 4-diketones.2 The bisenolate of 1,4-enediones obtained by reaction with Sn(SPy)2 reacts with an aldehyde to give 2-hydroxyalkyl-l,4-diketones. 

Schiff bases having two nitrogen atoms as donors may be derived either from condensation of dialdehydes and diketones with two molecules of an amine, or from reaction of diamines with aldehydes or ketones. In Section 20.1.2.1, it has been pointed out that coordination through the N atom may occur only under particular circumstances. However, in the case of diimines the formation of chelate rings stabilizes the metal-nitrogen bond. Thus, they can form both mono-41 and bis-chelate42 complexes. 

---