Synthesis of aromatic aldehydes

BORSCHE - BEECH Aromatic Aldehyde Synthesis Synthesis of aromatic aldehydes and of akyl aryl ketones from aldoximes or semcaibazones and aromatic dlazonum salts... 

GATTERMAN - KOCH Cartionylation Synthesis of aromatic aldehydes or ketones using cyanide salts or CO - HCI and Lewis adds. 

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-... 

The catalytic reduction of carboxylic acid chlorides by the Rosenmund procedure may be used for the preparation of aliphatic aldehydes but its application is mainly for the synthesis of aromatic aldehydes (e.g. Expt 6.120). Alternative procedures for the chemical reduction of acid chlorides include reduction with... 

Several procedures for the synthesis of aromatic aldehydes are available which involve the selective oxidation of a methyl group attached to an aromatic ring. A useful general reagent is a solution of chromium trioxide in acetic anhydride and acetic acid. The aldehyde is converted into the gem-diacetate as it is formed and is thus protected from further oxidation. The aldehyde is liberated from the diacetate by hydrolysis under acid conditions the yields, however, are frequently only moderate (e.g. p-nitrobenzaldehyde, Expt 6.117). 

If the acetic acid is replaced by methanol in the electrolyte, the electrochemical oxidation yields the corresponding benzaldehyde dimethyl acetals in excellent yields. This reaction which was discovered by BASF181), can also be used for the industrial synthesis of aromatic aldehydes. 

Catalysis by TEMPO has the advantage of being general for oxidation of both benzylic or non benzylic alcohols to aldehydes, whereas catalysis by PINO, although limited to the synthesis of aromatic aldehydes, has the advantage that the radical is generated in situ from the less expensive N-hydroxyphthalimide, which can be more easily recovered and recycled. 

A large number of methods exist for the preparation of aldehydes, many of which are very limited in their scope. The more general methods ate given here. An excellent review on the synthesis of aromatic aldehydes has been published. ... 

In the classical McFadyen-Stevens method, the Ar group in (40) is generally phenyl or p-tolyl and the conditions for the decomposition are sodium or potassium carbonate in ethylene glycol at 160 °C for ca. 2 min. This procedure is suitable for the synthesis of aromatic aldehydes, and appears to have been quite widely used. Table 10 shows a few examples many more are tabulated elsewhere. It can be seen that the best yields are obtained with electron rich aromatic nuclei. 

Synthesis From Alcohols.— The general methods of synthesis of aromatic aldehydes and ketones are several. The aldehydes may be prepared by the direct oxidation of the corresponding primary alcohol, usually with dilute nitric acid, e.g.. 

Improved Synthesis of Aromatic Aldehydes from Ozonolysis of Olefins... 

Gattermann and Gattennann-Koch formviation Synthesis of aromatic aldehydes using HCN or CO. 184... 

Toniolo, L., Graziani, M. Metals in organic syntheses. V. The Gattermann-Koch synthesis of aromatic aldehydes promoted by CuCI(PPh3) (n = 0,1 or 3). Is the cuprous complex necessary in the synthesis of tolualdehyde J. Organomet. Chem. 1980,194, 221-228. 

McFadyen-Stevens aldehyde synthesis.1 Use of this hydrazine in place of p-toluenesulfonylhydrazine for the McFadyen-Stevens synthesis of aromatic aldehydes has the advantage that decomposition of the intermediate acyl derivatives proceeds under mild conditions (K2C03 in refluxing CH3OH) however yields are unsatisfactory unless hydrazine is added. 

Step 2 Synthesis of aromatic aldehyde-activated phospholipid... 

Hass and Bender" developed a synthesis of aromatic aldehydes illustrated by the reaction formulated. 

F. Minisci, C. Punta, F. Recupero, F. Fontana, G. F. Pedulli, A new, highly selective synthesis of aromatic aldehydes by aerobic free-radical oxidation of benzylpic alcohols, catalysed by N-hydroxyphtalimide under mild conditions. Polar and enthalpic effects, Chem. Commum. (2002) 68. 

Aldehyde synthesis. A general method for the synthesis of aromatic aldehydes is illustrated by the reaction of mesitylene in methylene chloride and titanium tetrachloride on addition of dichloromethyl methyl ether to produce mesitylaldehyde.2... 

Different processes are proposed for the synthesis of aromatic aldehydes but only very few are satisfactory for industrial applications. 

Synthesis of aromatic aldehydes by formylation of phenols, pyrroles with CHCU-base (dichlorocarbene) (see 1st edition). 

If we wish to add just one carbon atom, as in the synthesis of aromatic aldehydes, we cannot use HCOCl since it does not exist. One of the most reliable methods is chloromethylation with CH2Q and HCl giving a CH2C1 group which can easily be oxidised to CHO (FGI). The important perfumery compound piperonal (12) can be made this way. Other methods of adding one carbon atom with a functional group are given in Table 2.). 

Aldehyde synthesis. Grignard reagents, RMgX, in THF react with this sulfoxide to form dimethyl dithioacetals of RCHO. These are deacetalated by sulfuryl chloride in the presence of wet silica gel. The method is particularly useful for synthesis of aromatic aldehydes. ... 

This reaction was initially reported by Hass and Bender in 1949. It is the synthesis of aromatic aldehydes by treatment of substituted benzyl halides with sodium nitropropane salt (also called sodium propane-nitronate ). Therefore, this reaction is called the Hass-Bender reaction or Hass-Bender oxidation. This reaction also takes place on aromatic polycyclic compounds. ... 

This reaction is useful for the conversion of the a-halomethylene group on an aromatic nucleus into a formyl group (i.e., in the synthesis of aromatic aldehydes.)... 

Louis Bouveault (Nevers, ii February 1864-Paris, 6 September 1909), assistant professor in the Paris Faculty of Sciences, worked out methods for the conversion of nitriles or amides to acids, the synthesis of aromatic aldehydes and acids by the use of aluminium chloride, the synthesis of aldehydes from nitro-olefins, and the reduction of aldehydes, ketones, and esters to alcohols by boiling with alcohol and sodium. ... 

The synthesis of aromatic aldehydes from aryl halides, carbon monoxide, and a hydride source has also been studied, but practical procedures for this process have been published only recently. Thus, the presentation of this process will be brief. The original formyla-tions of aryl halides were conducted with a tin hydride, as shown in Equation 19.88, or a silicon hydride. More recently, reactions were reported with formate as the hydride source (Equation 19.89). In fact, one of the earliest palladium-catalyzed reactions of aryl chlorides was the fonnylation of an aryl chloride to form aromatic aldehydes using... 

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