ALDEHYDES FROM AROMATIC

ALDEHYDES FROM ALLYLIC ALCOHOLS AND PHENYLPALLADIUM ACETATE 2-METHYL- 3-PHENYLPROPIONAL-DEHYDE, 51, 17 ALDEHYDES FROM AROMATIC NITRILES p-FORMYLBENZENE-SULFONAMIDE, 51, 20 ALDEHYDES FROM 2-BENZYL-4,4,6-TRIMETHYL—5,6-DIHYDRO-l, 3-(4H)-OXAZINE 1-PHENYLCYCLO-PENTANECARBOXYALDEHYDE, 51,... 

ALDEHYDES FROM AROMATIC NITRILES p-FORMYLBEN-ZENESULFONAMIDE, 51, 20 ALDEHYDES FROM 2-BENZYL-... 

This reaction can be used for the detection of aldehydes in the presence of ketones and for the differentiation of aliphatic aldehydes from aromatic ones. In a neutral medium aldehydes produce a black color or a precipitate other transient colors are sometimes formed which, in the case of aromatic aldehydes, last a bit longer. In an acid medium aliphatic aldehydes behave similarly as in a neutral medium, while in the presence of aromatic aldehydes a yellow color is produced first sometimes a precipitate is formed which persists for a certain time. Some other derivatives also react similarly to aide-hydes, such as, for example, cyanohydrins, aldehyde-ammonia adducts, sodium bisulfite addition compounds of aldehydes, and oximes. For modification with detection tubes containing the reagent see (62). 

The Gattermann-Koch synthesis is suitable for the preparation of simple aromatic aldehydes from ben2ene and its substituted derivatives, as well as from polycychc aromatics. The para isomers are produced preferentially. Aromatics with meta-directing substituents cannot be formylated (108). 

This procedure is representative of a new general method for the preparation of noncyclic acyloins by thiazol ium-catalyzed dimerization of aldehydes in the presence of weak bases (Table I). The advantages of this method over the classical reductive coupling of esters or the modern variation in which the intermediate enediolate is trapped by silylation, are the simplicity of the procedure, the inexpensive materials used, and the purity of the products obtained. For volatile aldehydes such as acetaldehyde and propionaldehyde the reaction Is conducted without solvent in a small, heated autoclave. With the exception of furoin the preparation of benzoins from aromatic aldehydes is best carried out with a different thiazolium catalyst bearing an N-methyl or N-ethyl substituent, instead of the N-benzyl group. Benzoins have usually been prepared by cyanide-catalyzed condensation of aromatic and heterocyclic aldehydes.Unsymnetrical acyloins may be obtained by thiazol1um-catalyzed cross-condensation of two different aldehydes. -1 The thiazolium ion-catalyzed cyclization of 1,5-dialdehydes to cyclic acyloins has been reported. 

Concern for the conservation of energy and materials maintains high interest in catalytic and electrochemistry. Oxygen in the presence of metal catalysts is used in CUPROUS ION-CATALYZED OXIDATIVE CLEAVAGE OF AROMATIC o-DIAMINES BY OXYGEN (E,Z)-2,4-HEXADIENEDINITRILE and OXIDATION WITH BIS(SALI-CYLIDENE)ETHYLENEDIIMINOCOBALT(II) (SALCOMINE) 2,6-DI-important industrial method, is accomplished in a convenient lab-scale process in ALDEHYDES FROM OLEFINS CYCLOHEXANE-CARBOXALDEHYDE. An effective and useful electrochemical synthesis is illustrated in the procedure 3,3,6,6-TETRAMETHOXY-1,4-CYCLOHEX ADIENE. ... 

Bismuth(III) acetate catalyzes the synthesis of azlactones (17) from aromatic aldehydes in moderate to good yields via the Erlenmeyer synthesis. While the standard procedure for azlactone synthesis consists of using a stoichiometric amount of fused anhydrous sodium acetate, 10 mol% of Bi(OAc)3 is sufficient to catalyze the reaction and the crude product is found to be > 98% pure. 

The wide range of applicability of the reaction can be seen from Table I. Formaldehyde, aliphatic aldehydes, and aromatic and hetero-... 

Most oxaziranes withstand temperatures of 100 C for a short time, e.g., on distillation. At higher temperatures isomerization and decomposition occur. Oxaziranes derived from aromatic aldehydes are here again differentiated from the alkyl-substituted oxaziranes. 

Oxazines are bases of varying strength and stability. Generally speaking, those which were derived by cyclization using aliphatic aldehydes are more stable than those formed from aromatic aldehydes. 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

A range of electron-withdrawing groups on the nitrogen - N-P(0)Ph2, N-tosyl, and N-SES, for example - were tolerated. Imines derived from aromatic, heteroaromatic, unsaturated, and even aliphatic aldehydes and ketones were employed... 

Treatment of selenoacetals 24 with butyllithium at 78 °C leads to the chiral a-seleno lithium compounds 25. Selenoacetals are stable compounds and can be readily prepared by selenoacetal-ization of the corresponding aldehydes25,26. In contrast to the corresponding dithioacetals, no competing deprotonation occurs on treatment with butyllithium, even with selenoacetals derived from aromatic aldehydes. 

Table 2. (S)-Cyanohydrins by Enzymatic Formation from Aromatic Aldehydes and Hydrocyanic Acid as well as (.S )-a-1 lydroxycarboxylic Acids by Hydrolysis20...

Nitriles from aromatic aldehydes, diammonium hydrogen phosphate, and 1-nitropropane, 43, 59 w-Nitrobenzenesulfonyl chloride, reduction to m-nitrophenyl disulfide by hydriodic acid, 40, 80 2 Nitro-2,3-dimethylbutane, 43, 89... 

AROMATIC HYDROCARBONS FROM AROMATIC KETONES AND ALDEHYDES 1,1 -DIPHENYLETH ANE (I,l -Ethylidenebisbenzene)... 

Abomatic Hydrocarbons from Aromatic Ketones and Aldehydes... 

ALCOHOL represents a convenient method of converting allyl alcohol to 2-substituted 1-propanols, while a one-pot reaction sequence of alkylation (alkyl lithium) and reduction (lithium—liquid ammonia) provides excellent yields of AROMATIC HYDROCARBONS FROM AROMATIC KETONES AND ALDEHYDES. 

At elevated temperatures, methylene carbons cleave from aromatic rings to form radicals (Fig. 7.44). Further fragmentation decomposes xylenol to cresols and methane (Fig. 7.44a). Alternatively, auto-oxidation occurs (Fig. 1.44b ). Aldehydes and ketones are intermediates before decarboxylation or decarbonylation takes place to generate cresols and carbon dioxide. These oxidative reactions are possible even in inert atmospheres due to the presence of hydroxyl radicals and water.5... 

Another example of a microwave-assisted 1,3-dipolar cycloaddition using azomethine ylides and a dipolarophile was the intramolecular reaction reported for the synthesis of hexahydrochromeno[4,3-fo]pyrrolidine 105 [70]. It was the first example of a solvent-free microwave-assisted intramoleciflar 1,3-dipolar cycloaddition of azomethine ylides, obtained from aromatic aldehyde 102 and IM-substituted glycinate 103 (Scheme 36). The dipole was generated in situ (independently from the presence of a base like TEA) and reacted directly with the dipolarophile present within the same molecifle. The intramolecu-... 

Addition of a masked Grignard reagent to an aldehyde or ketone From aromatic aldehydes and carbanions Bimolecular reduction of aldehydes or ketones... 

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