Amines 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). 

Under favourable circumstances, the initially formed /V-ylid reacts further through C-N cleavage. Thus, in the presence of a strong nucleophile, such as a phenoxide anion, the quaternary dichloromethylammonium cation forms an ion-pair with the phenoxide anion (Scheme 7.27), which decomposes to yield the alkyl aryl ether and the /V-formyl derivative of the secondary amine [22, 23]. Although no sound rationale is available, the reaction appears to be favoured by the presence of bulky groups at the 4-position of the aryl ring. In the absence of the bulky substituents, the Reimer-Tiemann reaction products are formed, either through the breakdown of the ion-pair, or by the more direct attack of dichlorocarbene upon the phenoxide anion [22,23],... 

Redox equations, balancing, 265 Reduction of aromatic compounds, 200 Reductive amination, 404 Reductive hydroboration, 95 Reformatsky reaction, 321 Regioselective reactions, 97 Reimer-Tiemann reaction, 438 Resonance, 23 in benzene, 192 energy, 24 structures, 29 Resorcinol, 327, 432 Retroaldol condensation, 399 Ring activation, 2(fiff Robinson inaction, 398 Rosenmund reduction, 306... 

Like other aromatic compounds, these five-membered heterocycles undergJ nitration, halogenation, sulfonation, and Friedel-Crafts acylation. They are mucji more reactive than benzene, and resemble the most reactive benzene derivatives (amines and phenols) in undergoing such reactions as the Reimer-Tiemann reaction, nitrosation, and coupling with diazonium salts. 

Intriguing but confusing information is available in two Chemical Abstracts references to Chinese publications. A 1988 abstract d reports the behavior of phenol under Reimer-Tiemann reaction conditions with the addition of tertiary amines. The authors claim that the para. ortho ratio is reversed from that normally observed and 60% yield of p-hydroxybenzaldehyde, 7% yield of o-hydroxybenzaldehyde and only 1% tars are obtained when phenol is subjected to the new conditions. One year later a report appeared in which it is claimed that the use of tertiary amines under phase-transfer conditions increases the yield of ortho product. The authors report a yield of 79% of salicylaldehyde from phenol using 0.37% catalyst (the nature of the catalyst is not mentioned in the abstract and the Chinese publication is not available to this author), and 35% sodium hydroxide at 55-60 °C for 90 min. Surely, these results (or the translation) warrant checking. 

A modified Reimer-Tiemann reaction was performed using tertiary amines to give the para-aldehyde as main product. A total phenol conversion of 74% together with 66% and 7% para-and orf/ o-aldehyde yield respectively, were obtained.Similarly, reaction of phenol and CHCI3 in an aqueous alkali solution in the presence of polyethylene glycol (PEG) gave after acid hydrolysis the para- and orf/ o-aldehyde in 75% and 16% yield... 

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. 

Reimer-Tiemann conversion of phenoxide into ortfto-hydroxybenzaldehyde involves an electrophilic attack by dichlorocarbene (Scheme 5.72). Carbenes also react with primary amines (carbylamine reaction) to give carbylamines (isonitriles) (Scheme 5.73). 

---