Aromatic compounds Azides

Z.B. Alfassi, R.H. Schuler, Reaction of azide radicals with aromatic compounds. Azide as a selective oxidant. Journal of Physical Chemistry 89 (1985) 3359—3363. 

Aromatic compounds that do not contain meta-directing groups can be converted to diarylamines by treatment with aryl azides in the presence of phenol at — 60°C ArH -f- Ar N3 —> ArNHAr. Diarylamines are also obtained by the reaction of N-arylhydroxylamines with aromatic compounds (benzene, toluene, anisole) in the presence of F3CCOOH ArH -f Ar NHOH ArNHAr. ... 

Sulfonylnitrenes are formed by thermal decomposition of sulfonyl azides. Insertion reactions occur with saturated hydrocarbons.255 With aromatic compounds the main products are formally insertion products, but they are believed to be formed through addition intermediates. 

The cydoaddition of different 1,3-dipoles such as azides [331, 341] and diazoalkanes [342-344] to acceptor-substituted allenes was thoroughly investigated early and has been summarized in a comprehensive review by Broggini and Zecchi [345], The primary products of the 1,3-dipolar cycloadditions often undergo subsequent fast rearrangements, for example tautomerism to yield aromatic compounds. For instance, the five-membered heterocycles 359, generated regioselectively from allenes 357 and diazoalkanes 358, isomerize to the pyrazoles 360 (Scheme 7.50) [331]. 

Electron-rich aromatic compounds, such as phenol, anisole and A,./V-dimethylaniline, add to bis(2-trichloroethyl) azodicarboxylate under the influence of lithium perchlorate, boron trifluoride etherate or zinc chloride to yield para-substituted products 74, which are transformed into the anilines 75 by means of zinc and acetic acid86. Triflic acid (trifluoromethanesulphonic acid) catalyses the reactions of phenyl azide with benzene, toluene, chlorobenzene and naphthalene, to give TV-arylanilines (equation 34)87. 

Amino-l,2,4-thiadiazoles (129) are diazotised at — 10°C in phosphoric acid, and couple in the usual way with reactive aromatic compounds such as naphthol, giving moderate yields of diazo dyes <82AHC(32)285>. Diazotization of (129) (R = H and Ph) may be accomplished using aqueous sodium nitrite and hydrochloric acid. Treatment of the resulting salt with sodium azide yields the 3-azido derivative (130) (Equation (17)) <86CC800>. 

Aromatic compounds that do not contain meta-directing groups can be converted to diarylamines by treatment with aryl azides in the presence of phenol at - 60°C ArH +... 

Figure 25-12 Isocratic HPLC separation of a mixture of aromatic compounds at 1.0 mL/min on a 0.46 x 25 cm Hypersil ODS column (C,8 on 5-jxm silica) at ambient temperature ( 22 C) (1) benzyl alcohol (2) phenol (3) 3, 4 -dimethoxyacetophenone (4) benzoin (5) ethyl benzoate (6) toluene (7) 2,6-dimethoxytoluene (8) o-methoxybiphenyl. Eluent consisted ot aqueous buffer (designated A) and acetonitrile (designated B). The notation 90% B in the first chromatogram means 10 vol% A and 90 vol% B. The buffer contained 25 mM KH2P04 plus 0.1 g/L sodium azide adjusted to pH 3.5 with HCI.

Another example is the photoreaction of tctrazolo[ 1,5- ]pyrimidinc 14 with aromatic compounds in the presence of trifluoroacetic acid (TFA) to give 2-(2-, 3-, and 4-substituted anilino)pyrimidines together with 2-aminopyridine and biphenyl or diarylmethanes. Here the key intermediate is also the 2-pyrimidylnitrenium ion originating from the photochemical decomposition of an imidoyl azide. This ion, depending on the reaction conditions, is present either in the singlet or triplet state and this governs the composition of the products (Scheme 11) <1998JP0478>. 

An ester group at C-3 or C-5 is not different in function from any ester in aliphatic or aromatic compounds. The ester can be converted into an amide or a hydrazide, or it may be hydrolyzed. The hydrazide can be converted into an acid azide and rearranged to an isocyanate which in turn will form a carbamate or can be hydrolyzed to an amine. However, the amine group can be replaced with chlorine by diazotization in hydrochloric acid, not an ordinary pattern of behavior (76AHC(20)65) although similar reactions do occur in the 1,2,4-triazole ring system. 

Various perhalo aromatic compounds as well as a series of heterocyclic precursors, such as, for instance, chloro-pyridazine or -triazine derivatives, gave rise to the corresponding azides, too." -" -" ... 

However, hydroxyl radicals are very reactive and known to react with aromatic compounds not only by electron abstraction but also by adding to the ring. Well-established, one-electron oxidizing radicals such as Br2 and N3, formed by pulsing a nitrous oxide saturated solution of potassium bromide or sodium azide, are used to produce cation radicals of the drug molecules. For example, the reactions that take place when a nitrous oxide aqueous solution of lO2 M potassium bromide in the presence of 10 4 M chlorpromazine (C1P) is subjected to pulse radiolysis (Asmus et al., 1979 Davies et al., 1979) are given below ... 

Bakers yeast catalyzes the reduction of azides and nitro compounds to amines128 2911. For example, it catalyzes chemoselective reduction of azidoarenes to arenamines as shown in Fig. 15-50[286, 287). Excellent yields are obtained for various aromatic compounds on reaction at room temperature. Aromatic nitro compounds... 

The acyl azide (142 R= CON3) has been photolysed in the presence of several aromatic compounds, e.g. benzene, anisole, or aniline. The nitrenes that were produced were in the triplet state, and yielded 3-substituted dihydronaphtho[2,l-Z)]pyrans (142 R=CONHPh, C0NHCeH40Me, or CONHNHPh respectively). Coumarins behaved similarly. Spectral examination has shown that the equilibrium between the butanedione and the cyclic hemiacetal structure (143 R = H, Me, or MeO) lies entirely on the latter s... 

Compounds, such as -diketones, containing reactive methylene groups react with aromatic sulfonyl azides in the presence of bases, affording a-diazo compounds.420,421... 

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