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Reimer-Tiemann reaction of phenol

The Reimer-Tiemann reaction of phenol with chloroform, in the presence of 50% NaOH, gives a much higher ratio of para to ortho hydroxy benzaldehyde when polyethylene glycol is used as compared to the established procedure without any addition of a hydrotope. A para to ortho ratio of 1 1 has been realized (Neumann and Sasson, 1986). [Pg.152]

Because of the differential partitioning of hydroxide and phenoxide anions into organic solvents by quaternary ammonium cations, the catalysts generally have little effect on the Reimer-Tiemann reaction of phenols with dihalocarbenes [15]. Cetyltrimethylammonium bromide has been used in the two-phase dichloromethyl-ation of polysubstituted phenols (Scheme 7.21, Table 7.10) under Makosza s conditions [16,17] ring expansion of the reaction products provides an effective route to tropones. The rate of the reaction is enhanced by ultrasonic radiation [16]. [Pg.342]

The presence of -OH group In phenols activates the aromatic ring towards electrophilic substitution and directs the Incoming group to ortho and para positions due to resonance effect. Reimer-Tiemann reaction of phenol 5delds sallcylaldehyde. In presence of sodium hydroxide, phenol generates phenoxlde Ion which Is even more reactive than phenol. Thus, In alkaline medium, phenol undergoes Kolbe s reaction. [Pg.74]

Hirao, K., Ikegame, M., Yonemitsu, O. Photochemical Reimer-Tiemann reaction of phenols, anilines, and indolines. Tetrahedron 1974, 30, 2301-2305. [Pg.663]

Ravichandran, R. P-Cyclodextrin mediated regioselective photo-Reimer-Tiemann reaction of phenols. J. Mol. Catal. A Chemical 1998,130, L205-L207. [Pg.663]

The photo-Reimer-Tiemann reaction of phenols with chloroform in the presence of 3-cyclodextrin has been reported to produce 4-hydroxy-benzaldehydes with high selectivity. ... [Pg.165]

In order to develop catalytic effects of cyclodextrins for bimolecular reactions, it needs to include two guest molecules simultaneously in a cyclodextrin (CD) cavity. Several examples of cyclodextrin-catalyzed bimolecular reactions have been reported. Rideout and Breslow have found that Diels-Alder reactions of cyclo-pentadiene with butenone, cyclopentadiene with acrylonitrile, and anthracene-9-carbinol with N-ethylmaleimide in water are markedly accelerated by 3-cyclodextrin (3-CD) (1). Komiyama and Hirai have reported site-selective Reimer-Tiemann reactions of phenols in cyclodextrin solutions (2). In most of these reactions, however, each substrate molecule is relatively small so that a 3-CD cavity may include simultaneously an additional reactant molecules. We found previously that the fluorescence quenching of pyrene and naphthalene by trimethylamine (TMA) or dimethylamine (DMA) in water is catalyzed by g-CD (3) Since the pyrene molecule is too large to be incorporated completely in the 3-CD cavity, it has been assumed that pyrene binds to a rim of the CD cavity to form a pyrene-capped CD complex and a remain-... [Pg.737]

The idea that dichlorocarbene is an intermediate in the basic hydrolysis of chloroform is now one hundred years old. It was first suggested by Geuther in 1862 to explain the formation of carbon monoxide, in addition to formate ions, in the reaction of chloroform (and similarly, bromoform) with alkali. At the end of the last century Nef interpreted several well-known reactions involving chloroform and a base in terms of the intermediate formation of dichlorocarbene. These reactions included the ring expansion of pyrroles to pyridines and of indoles to quinolines, as well as the Hofmann carbylamine test for primary amines and the Reimer-Tiemann formylation of phenols. [Pg.58]

Reimer-Tiemann formylation of phenols.1 Yields in this reaction can be increased by use of solid, powdered NaOH and addition of water (2 equiv. per phenol). [Pg.84]

Today an unequivocal determination of substituent positions on a phenol or naphthol or hydroxyaldehyde by infrared and NMR spectroscopy is usually straightforward and should always be performed routinely the major or most easily isolated product is sometimes not the expected one For example, the most easily isolated product (the first to crystallize) from a Reimer-Tiemann reaction of 3-chlorophenol is 6-chlorosalicylaldehyde, and not the 4-chloro isomer, which is the major product. [Pg.16]

The Reimer-Tiemann formylation of phenols with chloroform was attempted under sonication, in order to improve the frequently unsatisfactory yields. Optimal conditions make use of aqueous sodium hydroxide, and the electrophilic attack of the carbene on the ring is followed by the hydrolysis of the dichloromethyl group to the aldehyde. The advantages of the sonochemical method are not clearly apparent. The positive effect of sonication is limited to the reaction of 4-chlorophenol, and 4-methyl- and 4-methoxyphenol react with a yield lower than conventionally found. [Pg.150]

C7H6O2 Oily liquid of aromatic odour b.p. 196°C. (t is prepared by the action of chloroform and caustic potash on phenol (the Reimer-Tiemann reaction) or by the oxidation of the glucoside salicin. It is easily reduced to salicyl alcohol or oxidized to salicylic acid. [Pg.350]

The Reimer-Tiemann formylation of several phenols in the quinohne and pyrimidine series is known, but the reaction is unsuccessful with hydroxypyridines 3-hydroxypyridine gave a polymer. No 2-hydroxyquinoline appears to have been studied the 4-hydroxy... [Pg.75]

The formylation of a phenol 1 with chloroform in alkaline solution is called the Reimer-Tiemann reaction. It leads preferentially to formation of an ortho-formylated phenol—e.g. salicylic aldehyde 2 —while with other formylation reactions, e.g. the Gattermann reaction, the corresponding /jara-formyl derivative is obtained as a major product. The Reimer-Tiemann reaction is mainly used for the synthesis of o-hydroxy aromatic aldehydes. [Pg.238]

The applicability of the Reimer-Tiemann reaction is limited to the formylation of phenols and certain reactive heterocycles like pyrroles and indoles. Yields are usually below 50%. In contrast to other formylation procedures, the Reimer-Tiemann reaction is ort/zo-selective it is therefore related to the Kolb e-Schmitt reaction. [Pg.239]

Under suitable conditions, this can be a useful preparative method for cyclopropanes another preparative trapping reaction of CC12 is its electrophilic attack on phenols in the Reimer-Tiemann reaction (p. 290). [Pg.267]

Reimer-Tiemann reaction org chem Formation of phenolic aldehydes by reaction of phenol with chloroform in the presence of an alkali. rTm-or te-m3n re.ak-shon Reinecke s salt analychem (Ntf3)2Cr(SCN)4 NH4 H2O A reagent to detect mercury (gives a red color or a precipitate), and to isolate organic bases (such as proline or histidine). rTn-o-kez, s6lt ... [Pg.324]

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. [Pg.292]

Aldehyde formation Reimer-Tiemann reaction Treatment of a phenol with chloroform (CHCI3) and aqueous hydroxide introduces an aldehyde group (—CHO) onto the aromatic ring, generally ortho to the —OH group. A substituted henzalchloride is initially formed, but is hydrolysed by the alkaline medium. Salicylaldehyde can be produced from phenol by this reaction. Again, salicylaldehyde could be oxidized to sahcylic acid, which could be acetylated to aspirin. [Pg.134]

Phenols are smoothly converted into phenolic aldehydes by reaction with chloroform in the presence of base (the Reimer-Tiemann reaction). This overall formylation reaction is of interest in that it involves the generation from chloroform and alkali of the reactive intermediate, dichlorocarbene (2). This effects electrophilic substitution in the reactive phenolate ions giving the benzylidene dichloride (3) which is hydrolysed by the alkaline medium to the corresponding hydroxyaldehyde. The phenolic aldehyde is isolated from the reaction medium after acidification. [Pg.992]

Another example of minimizing the reaction steps necessary for synthesis is the direct conversion of cresols into hydroxybenzaldehydes, replacing the Reimer-Tiemann reaction in which phenol is reacted with chloroform in the presence of KOH. Hydroxybenzaldehydes are used in pharmaceuticals, perfumes, and colors. In the direct oxidation cresols are reacted with oxygen in the presence of Cu/Co/C catalysts forming the salicylaldehyde [49]. [Pg.25]

The Reimer-Tiemann reaction used to be an important way of making ortho-substituted phenols, but the yields are often poor, and modern industly is wary of using large quantities of chlorinated solvents. On a small, laboratory scale it has largely been superseded by ortholithiation (Chapter 9) and by modern methods outside the scope of this book. The mechanism probably goes something like this. [Pg.1069]

Treatment of a phenol with chloroform (trichloromethane) in the presence of hydroxide ion results in the synthesis of a 2-hydroxybenzalde-hyde through C-formylation. Dichlorocarbene, CCl2, is generated by the action of base on chloroform and this highly reactive electrophile then attacks the phenoxide. The mechanism of the Reimer-Tiemann reaction, is given in Scheme 4.12. [Pg.54]

Reimer-Tiemann Reaction. —Both the ortho- and para-hydroxy benzaldehydes are important. They may both be synthesized by what is known as the Reimer-Tiemann reaction. This consists of the interaction between a salt of a phenol and chloroform in the presence of an excess of alkali. The result is the introduction of the aldehyde group, (—CHO), into the benzene ring of the phenol as follows ... [Pg.659]

From Phenols by CCI4.—The Reimer-Tiemann reaction for the synthesis of hydroxy aldehydes (p. 659) is ... [Pg.717]

Reimer-Tiemann reaction. Synthesis of phenolic aldehydes. Dichlorocarbene... [Pg.804]

M.E. Jung and co-workers have developed a synthesis of selectively protected L-Dopa derivatives from L-tyrosine via a Reimer-Tiemann reaction followed by the modified Dakin oxidation. The formyl group introduced by the Reimer-Tlemann reaction had to be converted to the corresponding phenol. After trying many sets of conditions, the Syper process was chosen, which uses arylselenium compounds as activators for the oxidation. Treatment of the aromatic aldehyde with 2.5 equivalents of 30% hydrogen peroxide in the presence of 4% diphenyl diselenide in dichloromethane for 18h gave the aryl formate in excellent yield. This ester was cleaved by treatment with methanolic ammonia for 1h to afford the desired phenol in good yield. [Pg.119]


See other pages where Reimer-Tiemann reaction of phenol is mentioned: [Pg.378]    [Pg.378]    [Pg.1158]    [Pg.63]    [Pg.19]    [Pg.292]    [Pg.717]    [Pg.293]    [Pg.544]    [Pg.545]    [Pg.660]    [Pg.727]    [Pg.800]    [Pg.378]   
See also in sourсe #XX -- [ Pg.8 , Pg.33 , Pg.34 ]

See also in sourсe #XX -- [ Pg.8 , Pg.33 , Pg.34 ]




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Phenolation reaction

Phenols Reimer-Tiemann reaction

Reactions of Phenols

Reimer

Reimer-Tiemann

Reimer-Tiemann reaction

Tiemann reaction

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