Reductive diazotization

Table 2 summarizes some of the transformations of substituents which have been carried out on azetidines without effect on the ring <79CRV33l). Other transformations of interest are the base catalyzed epimerization, H exchange and alkylation of the activated H-3 in azetidines (26) (69JHC153) and the nitration, reduction, diazotization and hence further modification of the aromatic ring in 3-phenyl-fV-acetylazetidine (27) (61LA 647)83). 

The most suitable method of fast and simple control of the presence of dangerous substances is analytical detection by means of simplified methods - the so-called express-tests which allow quickly and reliably revealing and estimating the content of chemical substances in various objects. Express-tests are based on sensitive reactions which fix analytical effect visually or by means of portable instalments. Among types of indicator reactions were studied reactions of complex formation, oxidation-reduction, diazotization, azocoupling and oxidative condensation of organic substances, which are accompanied with the formation of colored products or with their discoloration. 

This method is an adaptation of that of Dengel. -Methoxy-phenylacetonitrile can also be prepared by the metathetical reaction of anisyl chloride with alkali cyanides in a variety of aqueous solvent mixtures by the nitration of phenylaceto-nitrile, followed by reduction, diazotization, hydrolysis, and methylation 1 by the reduction of ct-benzoxy- -methoxy-phenylacetonitrile (prepared from anisaldehyde, sodium cyanide, and benzoyl chloride) and by the reaction of acetic anhydride with the oxime of -methoxyphenylpyruvic acid. ... 

The examples that are treated below are those sequences where all steps - except the last — are preparations for a color or fluorescence derivatization reaction which is carried out in the last step, i. e. they can be regarded as a sort of selective in situ pretreatment for a final detection reaction. Such reaction sequences are frequently necessary because all the reagents cannot be mixed together in a single solvent, or because it is necessary to dry, heat or irradiate with UV light between the individual reaction steps. The detection of aromatics by the reaction sequence nitration — reduction — diazotization - couple to form an azo dye is an example of this type (Fig 21). 

Fig. 21 Reaction scheme for the detection of aromatics, by means of the reaction sequence, nitration, reduction, diazotization and coupling to an azo dye, and of aliphatic nitro compounds by detection of the primary amino group produced on reduction.

Attempts to remove the amino group from 5-amino-l,2,4-thiadia-zole by its reductive diazotization, in the presence of ethanol or hypo-phosphorous acid,198 were not successful. 

A photoreactive analogue, 2 -azidoAP (574ee) was prepared as shown in Scheme 3.120 [242], Intermediate (582) was synthesized from 2-nitro-4-amino-benzoic acid by protection of the amino group, reduction, diazotization and peptide coupling. 

These structures were confirmed by syntheses. The amide 3 prepared from known compounds was reacted with phosphorus oxychloride in acetonitrile to generate a dihydroisoquinoline which on reduction, diazotization, and treatment with activated copper gave dihydro-imeluteine. Dehydrogenation to the natural alkaloid was effected by... 

The dithiophenol derivative 315, prepared from the dinitro 314 via reduction, diazotization, and subsequent reaction with sulfide, under mild oxidative conditions, afforded the cyclic disulfide 310, which was converted into dioxide 316 with hydrogen peroxide or a peracid (Scheme 66) <2004W0099162>. The already known, dithiocin 310, obtained... 

The synthesis of quinones from arenes is an area which demands further research, despite the number of reagents presently available for this transformation. This is highlighted by the synthesis of the naphthoquinone (3). Direct oxidation of the dibromoarene (1) was unsatisfactory, and therefore Bruce and coworkers had to resort to a multistep sequence involving nitration, reduction, diazotization, displacement by hydroxide and finally oxidation of the phenol (2) with Fremy s salt (Scheme 1). Although there are examples of the oxidation of polynuclear aromatic hydrocarbons to quinones, the direct oxidation of an arene to a quinone is a process not encountered in the synthesis of more complex mt ecules. 

Since reduclion of nitro groups to amino groups can be realized in aqueous tetrafluoroboric acid media, it is not always necessary to start from the isolated amine in order to carry out a fluorodeamination via the Balz-Schiemann process. Thus, it is possible to start from the nitro derivative, to obtain the corresponding fluoro derivative, in a three-step, one-pot process (reduction, diazotization. fluorodediazoniation). ... 

A - 2-(4-flnoro-lW-imidazol-5-yl)ethyl]acetaiiiide (a-jV-Acetyl-4-fluorohistamine, 23) I ypical Procedure for One-Pot Nitro Reduction, Diazotization, and Photochemical Fluorodediazoniation ... 

Keto esters, such as methyl acetoacetate and methyl benzoylacetate, have been converted to carbethoxyketenes by nitrosation, reduction, diazotization, and finally decomposition of the intermediate diazoketo... 

Schnider and Grtissner in the same way prepared 3- and 2- (or 4) hydroxy-N-methylmorphinane, obtained the same compounds from N-methylmorphinane by way of the nitro and amino compounds, and also synthesized the 3-hydroxy-derivative from [liv] by nitration, reduction, diazotization, c., followed by cyclization [25]. They have more recently resolved [lxxih] and prepared 3-hydroxy-N-allyl-morphinane [26], Schnider and Hellerbach [27] prepared an isomer of [lxxiii] and also synthesized dZ-tetrahydrodesoxycodeine [lxxv] by the cyclization of [lxxvi], in which reaction a small amount of 2 3-dihy-droxy-N-methylmorphinane [lxxvii], isomeric with dZ-tetrahydrodes-oxymorphine, was also obtained. Both [lxxhi] and [lxxvii] exhibit marked analgesic properties to about the same extent, whilst the 2- (or 4) hydroxy-compound is much less active [25, 27]. 

Condensation of the latter with 6-nitropiperonal, followed by reduction, diazotization, heating in the presence of copper powder, and finally decarboxylation in quinoline gave an overall yield of 4% of the sanguinarine 176). 

Barger (80) starting from phenethyl alcohol, obtained phenethyl chloride, which, when heated with dimethylamine, yielded dimethyl-phenethylamine. By nitration, reduction, diazotization, etc. a base identical with natural hordenine was obtained. Rosenmund (81) condensed p-methoxybenzaldehyde with nitromethane and reduced the alkoxy nitrostyrene to p-methoxyphenethylamine. With methyliodide a mixture of bases was formed from which, after demethylation with boiling hydroiodic acid, hordenine was obtained in low yield. Voswinckel... 

For methods of converting nitro substituents to other groups by reduction, diazotization and substitution, see pp. 520 and 567, and Chapters 22 and 24. 

The second new synthesis of 7-methoxymitosene (3) was published by Wender and Cooper [34]. Based on a novel triazole photolysis, it affords the product in 8.3% yield after 12 steps. It is more efficient than the original synthesis of 3, but it requires more steps than the synthesis reported by Luly and Rapoport in 1984. As illustrated in Scheme 12, it began with 2,6-dimethoxytol-uene (91), which was converted into azido derivative 92 by the sequence of nitration, catalytic reduction, diazotization, and treatment with sodium azide. Dimroth condensation of 92 with ethyl 6-triisopropylsiloxy-3-oxohexanoate in... 

Physical constants of several partially fluorinated biphenyls (up to the 2,2, 3,4, -5,5, 6-heptafluoro-compound), obtained by a range of classical methods including the Friedel-Crafts, Ullmann, and Balz-Schiemann reactions, have been reported, and 1,8-difluoro- or 1,4,5-trifluoronaphthalene may be obtained by conventional routes (nitration, reduction, diazotization) from 1,8-diamino- or 1,5-difluoro-naphthalene, respectively. ... 

Barger (22) synthesized the base by reduction of p-hydroxyphenyl-acetonitrile with sodium. Barger and Walpole (33) later described two other syntheses. The p-hydroxy group was introduced into phenyl-ethylamine by nitration, reduction, diazotization etc., or anisaldehyde was converted to p-methoxyphenylpropionamide, from which, by Hofmann degradation and demethylation, tyramine was obtained. Hosen-mund (34) condensed anisaldehyde with nitromethane, and obtained tyramine by reduction followed by demethylation. Further syntheses of tyramine have been described by Kondo and Shinozaki (35), Slotta and Altner (36), Koessler and Hanke (37), Kindler and Peschke (38) and Buck (39, 40). A well known method of preparation is the thermal decarboxylation of tyrosine. Waser (41) obtained a 96% yield by heating the amino acid suspended in a high boiling solvent (fluorene). 

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