ALDEHYDES FROM 2-BENZYL

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 2-BENZYL-4,4,6-TRIMETHYL-5,6-DIHYDRO-l,3(4H)-OXAZINE ... 

Politzer, I.R., and Meyers, A.L, Aldehydes from 2-benzyl-4,4,6-trimethyl-5,6-dihydro-l,3(4/7)-oxazine. 1-Phenylcyclopentanecarboxaldehyde, Org. Synth. Coll., VI, 905, 1988. 

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

TEMPO has a double role - it generates the oxoamonium salt, responsible for the oxidation (Scheme 1), and inhibits the further oxidation of aldehydes and ketones, which occurs instead via free-radical chain processes under the same conditions, but in the absence of TEMPO [5a], Thus, this catalytic system is highly effective for one of the most demanding transformations, the selective synthesis of aldehydes from benzylic and nonbenzylic alcohols. 

Nitrosobenzene, CjHsNO, which is obtained by the oxidation of phenylhydroxylamine, and p>nitrosodimethylaniline, p-(CH3)2NCjH4NO, which is easily prepared by the nitrosation of dimethylaniline, are fairly specific oxidizing agents for the preparation of aromatic aldehydes from benzyl halides or tosylates and of a-dicarbonyl compounds from from a-halo ketones [984, 985]. Also, a methylene group flanked by two carbonyls can be oxidized to a carbonyl group by nitrosodimethylaniline [986]. Pyridine is frequently used to form quaternary pyridinium salts from reactive halides prior to their oxidation to aromatic aldehydes, a-ketoaldehydes, or a-diketones [984] (equations 22 and 23). 

The oxidation of benzylic halides to aromatic aldehydes and ketones is very easy and is accomplished by many reagents. Very simple ways to prepare aromatic aldehydes from benzyl chlorides and bromides are treat-... 

Zr compounds are also useful as Lewis acids for oxidation and reduction reactions. Cp2ZrH2 or Cp2Zr(0 Pr)2 catalyze the Meerwein-Ponndorf-Verley-type reduction and Oppenauer-type oxidation simultaneously in the presence of an allylic alcohol and benzaldehyde (Scheme 40).170 Zr(C)1 Bu)4 in the presence of excess l-(4-dimethylaminophenyl) ethanol is also an effective catalyst for the Meerwein-Ponndorf-Verley-type reduction.1 1 Similarly, Zr(0R)4 catalyze Oppenauer-type oxidation from benzylic alcohols to aldehydes or ketones in the presence of hydroperoxide.172,173... 

ALDEHYDES FROM PRIMARY ALCOHOLS BY OXIDATION WITH CHROMIUM TRIOXIDE 1-HEPTANAL, 52, 5 ALDEHYDES FROM sym-TRITHIANE n-PENTADECANAL, 51, 39 Aldehydes, acetylenic, 54, 45 Aldehydes, aromatic, 54, 45 Aldehydes, benzyl, 54, 45 Aldehydes, olefinic, 54, 45... 

Optimum reaction conditions for the preparation of l-d-aldehydes from aryl, benzyl, and vinyl organometallics are under investigation by the submitters. 

The formation of carbanions, according to Scheme 6, has been much studied but has proved to be of little preparative use. The benzyl anion, generated from benzyl-dimethylsulphonium tosylate, reacted with acrylonitrile but the addition product was formed in only low yield Similarly the reactive ylid formed by deprotonation of trimethylsulphonium salts has been cathodically generated and trapped by several aldehydes and ketones as well as ethyl maleate and fumarate examples are given in Scheme 7. For the best case (benzophenone), the epoxide was formed in 40%... 

When treating the overall transformation kinetics of an organic compound as we have done for the hydrolysis of benzyl chloride (Eq. 12-11), we assume that the reverse reaction (i.e., the formation of benzyl chloride from benzyl alcohol) can be neglected. For many of the reactions discussed in the following chapters we will make this assumption either because the reverse reaction has an extremely small rate constant (i.e., the reaction is practically irreversible), or because the concentration ) of the reactant(s) are very large as compared to the concentration(s) of the product(s). There are, however, situations in which the reverse reaction has to be taken into account. We have already encountered such a reaction in Illustrative Example 12.1. To demonstrate how to handle the reaction kinetics in such a case, we use the hydration of an aldehyde to yield a diol (Fig. 12.3). This example will also illustrate how the equilibrium reaction constant, Kn is related to the kinetic rate constants, kY and k2, of the forward and reverse reaction. 

Isatin has been used in the Strecker degradation of a-amino acids to aldehydes,434-437 and in the formation of benzaldehydes from benzyl-amines.431,435,438-440 These conversions have been the subject of a review, and mechanisms have been proposed.441 This formation of aldehydes from primary amines may, in part, explain some of the... 

It is difficult to prepare fluorinated aldehydes from the corresponding alcohols. The reason is that the initially formed aldehyde is usually immediately oxidized to a carboxylic acid. When the oxidation is only partially successful, then there is also the difficulty of separating the aldehyde from the starting alcohol. The oxidation of benzylic alcohols having a fluorinated... 

With nonpersistent nitroxyl radicals (PINO, Scheme 2) benzyl alcohols give, selectively, the aromatic aldehydes, whereas aliphatic alcohols lead to the carboxylic acids [12], even at low conversions [6], This behavior has been explained on the basis of the prevailing polar effect [6, 13] in the abstraction of hydrogen from benzyl alcohols and by the dominant enthalpic effect in the abstraction of hydrogen from aliphatic alcohols [6[. 

Optically active (—)-sparteine, a piperidine-derived alkaloid complexed with palladium chloride 33, has been used in the enantioselective oxidation of benzyl alcohol derivatives <2005JA14817>. 4-Hydroxy-TEMPO 34 serves as an efficient catalyst for the continuous production of aldehydes from alcohols and bleach in a tube reactor (TEMPO = 2,2,6,6-tetramethyl-piperidine-l-oxyl) <20050PD577>. 

The production of hydrocarbons from aromatic alcohols is most readily explained by the hydrogenolysis of the alcohol, but an alternate possibility should be considered. The formation of an aldehyde and its subsequent decarbonylation under reaction conditions could lead to the hydrocarbon. Both toluene and 2-phenylethanol, the mixture of products secured from benzyl alcohol, may be regarded as derived from phenylacetaldehyde as an intermediate ... 

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