Phenol with chloroform

Although 4-hydroxybenzaldehyde can be made by the saligenin route, it has been made historically by the Reimer-Tiemann process, which also produces sahcylaldehyde (64). Treatment of phenol with chloroform and aqueous sodium hydroxide results in the formation of benzal chlorides, which are rapidly hydrolyzed by the alkaline medium into aldehydes. Acidification of the phenoxides results in the formation of the final products, sahcylaldehyde and 4-hydroxybenzaldehyde. The ratio of ortho and para isomers is flexible and can be controlled within certain limits. The overall reaction scheme is shown in Figure 1. Product separation is accomphshed by distillation, but this process leads to environmental problems because of the quantities of sodium chloride produced. 

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). 

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 ... 

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. 

Regioselective reaction of phenols. Reaction of phenols with chloroform in aqueous alkaline solution catalyzed by P-cyclodextrin results in virtually complete attack at the para-position by dichlorocarbene to give, after hydrolysis, 4-hydroxybenzaldehydes. If the para-position is substituted, 4-(dichloromethyl)-2,5-cyclohexadienones are obtained as the major product. The selectivity results from formation of a ternary complex from P-cyclodextrin, chloroform, and the phenol. ... 

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. 

Formylation of Phenols with Chloroform (Reimer-Tiemann). 

Reimer-Tiemann reaction. Reaction for the formation of phenolic aldehydes by heating a phenol with chloroform in the presence of alkali. 

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. ... 

The Reimer-Tiemann reaction10611 601 — treatment of a phenol with chloroform in an alkaline medium — also leads to aldehydes ... 

Hydroxyl derivatives of aldehydes are usually prepared by what is known as the Tiemann-Reimer reaction, which consists in condensing a phenol with chloroform in the presence of an alkali. It is probable that the reaction takes place in steps as indicated by the following equations —... 

The best way to introduce the formyl group in the proper position is through a Reimer-Tiemann reaction. This involves treating a phenol with chloroform in the presence of base. Under these conditions, chloroform sequentially loses a proton and a chloride anion in an a-elimination (elimination with both leaving groups on same carbon) to form a dichlorocarbene. 

The reaction of phenol with chloroform and alkali (dichlorocarbene) at 65 to 70 °C gives salicylaldehyde (Reimer-Tiemann synthesis), from which coumarin is produced by reaction with acetic anhydride and sodium acetate at 135 to 155 °C (Perkin reaction). Coumarin is used as a perfume and fragrance. 

ABSTRACT. Selective formylation of phenol at the 4-position is achieved by using 3-cyclodextrin as catalyst in the reaction of phenol with chloroform in aqueous alkali. The reactions of 1,3-dihydroxybenzene and indol, respectively, in the place of phenol give 2,4-dihydroxybenz-aldehyde and indole-3-aldehyde in virtually 100% selectivies and high yields. The reactions of para-substituted phenols, 4-methylphenol and 5,6,7,8-tetrahydro-2-naphthol, instead of phenol, effect the selective dichloromethylation at the para-positions. Selective carboxylation of phenol at the 4-position is achieved in the reaction of phenol with carbon tetrachloride in aqueous alkali by using 3-cyclodextrin and copper powder as catalyst. 

In the absence of CyD, the reaction of para-substituted phenol with chloroform in aqueous alkali gives 4-dichloromethy1-2,5-cyclohexadienone in low yield. 

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. 

Formylation of phenol with chloroform in a basic medium was first proposed in 1876 by Reimer and Tiemann. Treatment of phenol with aqueous chloroform and aqueous... 

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