Of aryl aldehydes

LAPWORTH (BENZOIN) Condensation Condensation of two molecules of aryl aldehydes fo an alpha-hydroxy ketone catalysed by CN (via cyanohydnns). 

While the Friedel-Crafts acylation is a general method for the preparation of aryl ketones, and of wide scope, there is no equivalently versatile reaction for the preparation of aryl aldehydes. There are various formylation procedures known, each of limited scope. In addition to the reactions outlined above, there is the Vdsmeier reaction, the Reimer-Tiemann reaction, and the Rieche formylation reaction The latter is the reaction of aromatic compounds with 1,1-dichloromethyl ether as formylating agent in the presence of a Lewis acid catalyst. This procedure has recently gained much importance. 

Ketonitriles Preparfx) by Cyanide-Catalyzed CoNJuoArii Addition of Aryl Aldehydes to a,0-UNSATURATED Nitriles... 

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

CYANIDE-CATALYZED CONJUGATE ADDITION OF ARYL ALDEHYDES 4-(3-PYRIDYL)-4-OXOBUTYRONITRILE... 

Fe. Iron metal was found to be able to mediate the allylation reactions of aryl aldehydes with allyl bromide using sodium fluoride as the promoter. The formation of an allyliron species was proposed as the reactive intermediate in the reaction (Scheme 8.20).187 In view of... 

The sodium bromide catalyzed three-component cyclocondensation of aryl aldehydes, CH-acidic nitriles, and dimedone under solvent-free conditions has been studied by Devi and Bhuyan (Scheme 6.245) [429]. Utilizing equimolar amounts of the building blocks and 20 mol% of sodium bromide as catalyst, microwave irradia-... 

Jacobsen and co-workers14 have shown that a tridentate Schiff base chromium complex 13 catalyzed an asymmetric carbonyl-ene reaction between a variety of aryl aldehydes (14, Equation (8)) and 2-methoxy propene 15 or 2-trimethylsiloxypropene. The highest yields were afforded when the aryl ring was substituted with an electron-withdrawing group however, the substituent did not seem to affect the enantioselectivity. 

Indeed the only conversion where biocatalysis should be seriously considered is the transformation of aldehydes into optically active cyanohydrins1 2. For example, the conversion of aryl aldehydes into the appropriate (R)-cyanohydrins using almond meal may be accomplished in quantitative yield and gives products... 

The coupling of aryl aldehydes and ketones to give chiral diols can be achieved by reaction with the tetraphenyl-germole dianion 99 (Equation (212), Table 29).17 Hexamethyldigermane can be employed to generate synthetically important allylgermanes with high stereoselectivity (Equation (213), Table 30), and the reaction pathway for this process has been proposed.267... 

Trimethylsilylation of enolizable carbonyl compounds and alcohols has also been accomplished by the fluoride ion promoted reaction with hexamethyldisilane and ethyl trimethylsilylacetate [48, 49], with high stereospecificity giving Z-enol ethers from ketones [50]. l-Trimethylsilyl-(l-trimethylsilyloxy)alkanes, produced from the reaction of aldehydes with hexamethyldisilane, undergo acid-catalysed hydrolysis during work up to yield the trimethylsilylcarbinols [51]. In the case of aryl aldehydes, the initially formed trimethylsiloxy carbanion produces the pinacol (Scheme 3.1). 

Condensation of aryl aldehydes with methyl methylthiomethyl sulphoxide... 

Under basic liquiddiquid two-phase conditions the reaction of aryl aldehydes with benzyldibutyltelluronium bromide produces oxiranes [71] although, in some instances, alkenes are formed. 

The catalysed reaction of aryl aldehydes with ammonia and chloroform (7.4.3) in the presence of chiral ephedrinium salts leads to the asymmetrically induced formation of a-amino acids. Yields are variable and with ca. 20-30% ee [49]. 

Cyanide-catalyzed condensation of aryl aldehyde to benzoin. Now cyanide is mostly replaced by a thiazolium salt. Cf. Stetter reaction. 

Oxidation of aryl aldehydes or aryl ketones to phenols using basic hydrogen peroxide conditions. Cf. Baeyer-Villiger oxidation. 

The radical cations (47) produced by T oxidation of aryl aldehyde hydrazones acted as 1,3-dipoles in reaction with nitriles to form, after a second T oxidation, 1,2,4-triazoles (Scheme 4) (85TL5655). 

Grigg et al. (34) also conducted extensive studies of the thermal 1,2-prototropic generation of azomethine ylides and this can be exemplihed by the diastereofacially selective cycloaddition of 7-aminocephalosprin ylide precursors. Condensation of aryl aldehydes with 120, in refluxing toluene, furnished imines 121, which, in the presence of A -phenylmaleimide, furnished a mixture of cycloadducts 122 and 123 in essentially quantitative yield in a 2 1 ratio. The only observed products... 

Native BAL is a versatile catalyst in the stereoselective carboligation of aryl aldehydes (Scheme 3.2.1), yielding R-configured benzoins with 99% ee [21]. 

Imidazole synthesis. A new synthesis of 4,5-diarylimidazoles (2) involves reaction of catalytic amounts of aqueous elhanolic K.CN with N-methyl-C-aryl nitrones (1), prepared by condensation of aryl aldehydes with N-methyl-hydroxylamine. The reaction involves an intermediate cyanoimine (n). 

Aromatic thioaldehyde pentacarbonylmngsten(O) complexes were synthesized by treatment of iV-phenyl or A -cyclohexyl imines of aryl aldehydes with [PPh4][W(CO)5SH] in CH2CI2 or CgHg in the presence of BF3 OEt2 and MeCC H (reaction 165) ... 

The synthesis of alkylbenzenes may be classified under (a) the Wurtz-Fittig reaction (b) the reduction of aryl aldehydes and ketones and (c) and Friedel-Crafts alkylation reaction. 

Alkaline silver oxide is the most satisfactory reagent for oxidation of the aldehyde 3 to the acid 4.2 This reagent has been recommended for oxidation of aryl aldehydes (1,1012-1013), but only moderate yields have been reported for oxidation of a,/ -enals with Ag20.3 Apparently, the successful results in the oxidation of 3 are the result of the activating effect of the keto group. 

Aryl diazoalkanes (Bamford Stevens reaction of aryl aldehydes or ketones to form aryl diazoalkanes. The products were generally identified as the corresponding I.S-dinilroben/oalc esters. (equation 1). ... 

BINOL-derived phosphoramidites are versatile ligands in palladium-catalysed umpol-ung allylation of aryl aldehydes mediated by diethylzinc.172 The possible roles of allyl-zinc and -palladium species in the mechanism are discussed in detail. 

Organocata lytic Enantioselective Morita-Baylis-Hillman Reactions Table 5.4 MBH reaction of aryl aldehydes and MVK catalyzed by /MCD. 

The condensation product of dithiooxamide with benzaldehyde has been shown to be 2,5-diphenylthiazolo[5,4-d]thiazole (equation 75) (60JA2719). Its formation involves dehydration of the reactants and further dehydrogenation. The reaction is comparable in scope with condensations such as the Perkin reaction, and many 2,5-diarylthiazolo[5,4-c ]thiazoles have been prepared from a variety of aryl aldehydes. Condensation products were not obtained from simple aliphatic aldehydes (71JMC743). 

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