Aldehydes Reimer-Tiemann reaction

Phenyhsonitrile has a powerful characteristic odor it is used as a qualitative test (the carbylamine test) for chloroform or primary aromatic amines. Chloroform reacts with phenols in alkaline solution to give hydroxyaromatic aldehydes in the Reimer-Tiemann reaction eg, phenol gives chiefly Nhydroxyben2aldehyde and some sahcylaldehyde (11) (see Hydroxybenzaldehydes). 

Pyrrolo[2,3-6]pyridine, 2-methyl-Reimer-Tiemann reaction, 4, 508 Pyrrolo[2,3-6]pyridine, 4-methyl-hydrogen exchange, 4, 502 reaction with aldehydes, 4, 503 reaction with benzaldehyde, 4, 511... 

The Ciamician-Dennstedt reaction can be thought of as the complement to the Reimer-Tiemann reaction (Scheme 8.3.2). The first step of both reactions is cyclopropanation of one of the carbon-carbon double bonds of a pyrrole with a dichlorocarbene, resulting in intermediate 3. The Ciamician-Dennstedt reaction results from cleavage of the internal C-C bond and elimination of chloride (path a), while the Reimer-Tiemann reaction results from cleavage of the exocyclic bond, and subsequent hydrolysis of the dichloromethyl moiety to furnish aldehyde 5 (path b). 

Under conditions more similar to those of the Reimer-Tiemann reaction 3-bromopyridine was obtained from pyrrole and bromo-form. Treatment of pyrrole with chloroform and aqueous alkali gave pyrrole-2-aldehyde curiously, the formation of 3-chloropyridine under these conditions does not appear to have been reported, in spite of being frequently quoted. However, indole gave both indole-3-aldehyde and 3-chloroquinoline under these conditions [Eq. (10)]. 

While the Friedel-Crafts acylation is a general method for the preparation of aryl ketones, and of wide scope, there is no equivalently versatile reaction for the preparation of aryl aldehydes. There are various formylation procedures known, each of limited scope. In addition to the reactions outlined above, there is the Vdsmeier reaction, the Reimer-Tiemann reaction, and the Rieche formylation reaction The latter is the reaction of aromatic compounds with 1,1-dichloromethyl ether as formylating agent in the presence of a Lewis acid catalyst. This procedure has recently gained much importance. 

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. 

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. 

Eydroxy-5,6,7,8-tetrahydro-l-napMhaldehyde was prepared [7] by the Reimer-Tiemann reaction cn 5,6,7,8-tetrahydro- 2-naphthol. Three recrystallizations from aqueous alcohol afforded a very low yield of pure aldehyde, m.p. 86-8-87-8° (spectral sample) lit. m.p. 86-87° [7J. 

Methylpyrrolo(2,3-6]pyridine reacts with dichlorocarbene (Reimer-Tiemann reaction) to give the aldehyde (51) with no trace of a ring-expanded product (68AHC(9)27). On the other hand, the 2-phenyl compound gives the chloropyridine (52) and no aldehyde... 

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. 

Answer Procedure X-3 which is the oxidation of a methyl group attached to an aromatic ring. A procedure Tor placing an aldehyde function ortho to an -OH group on an aromatic ring is tile Reimer-Tiemann reaction,. It proceeds as illustrated... 

Under the conditions of the Reimer-Tiemann reaction, 2-methyl-1 //-pyrrolo[2,3-/>]pyridine (57) gave the aldehyde (58) without any ring-expanded products (Equation (9)) <68AHC(9)27>. 

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 ... 

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

Reimer-Tiemann reaction. Phenolic aldehydes. Discussed in Sec. 24.12. 

Reimer-Tiemann reaction. Synthesis of phenolic aldehydes. Dichlorocarbene... 

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