Bucherer reaction, application

Bucherer reaction Bucherer discovered that the interconversion of 2-naphthol and 2-naphthylamine through the action of alkali and ammonia could be facilitated if the reaction was carried out in the presence of (HSO3]" at about 150 C. This reaction is exceptional for the ease with which an aromatic C —OH bond is broken. It is not of general application, it is probable that the reaction depends upon the addition of [HSO3]" to the normally unstable keto-form of 2-naphthol, and subsequent displacement of —OH by —NH2. 

The Bucherer reaction is also applicable with certain compounds in the benzene and anthracene series, but it is of practical significance only with naphthalene compounds. The reaction can be used with both a- and -naphthols or... 

The mechanism of the Bucherer reaction has been clarified by Rieche and Seeboth 565 its preparative details, selectivity, and applicability have been reviewed by Drake567 and Seeboth.568... 

Note on Bucherer reaction (BR) The reaction (Figure 2.19) concerns naphthalene compounds and is not applicable to the benzene series. The mechanism of the reaction has been worked out by Rieche and Seeboth (1960) the rate-determining step in the above being considered to be the interconversion of the tetralonedisulphonic acid and imino derivative... 

A particularly useful application of MW-assisted synthesis at elevated pressure has been in the preparation of radiopharmaceuticals containing isotopes with short half-lives, such as C-ll (half-life 20 min) and F-18 (half-life 110 min) [25-27]. Clearly, these compounds have to be synthesized very rapidly in order to give products with high radiochemical yield. For example, [1-11C] tyrosine 12 was synthesized using the two step Bucher-Strecker method by the reaction of p-hydroxyphenylacetaldehyde bisulfite adduct 11 with K11CN and (NH4)2C03 followed by hydrolysis with aqueous NaOH (Scheme 4.7)... 

The Bucherer-Bergs synthesis is of general application to carbonyl compounds, employing potassium cyanide and ammonium carbonate.1,4 Carbonyl derivatives such as semicarbazones, thiosemicarbazones, oximes, azines, phenylhydrazones, imidazolidines, and azomethines also are readily converted directly to the corresponding hydantoins 44 The extent to which the reaction occurs appears unrelated to the hydrolytic stability of the starting material. The proposed mechanism is given in Scheme 1. 

Synthesis.—Optimum conditions have been systematically worked out for the preparation of the spiro-4-thiohydantoin (217) from cyclohexanone hydrolysis of (217) leads to the corresponding a-amino-acid. " This overall Bucherer-Bergs reaction is a useful alternative to the classical Strecker synthesis and hopefully the optimum conditions found will be applicable to other ketones. Hydrolysis of 5-substituted hydantoins can be effected enzymatically, giving optically active a-amino-acids of varying purity. ... 

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