Reaction of aromatic azides with strong acids: formation of fused nitrogen heterocycles and arylamines

Abstract

Descrevemos neste trabalho a ação de ácido trifluoroacético, ácido trifluorometanossulfônico e cloreto de alumínio sobre aril azidas orto-substituídas para formar indóis, azepinas e arilaminas com bons rendimentos. As azidas protonadas perdem nitrogênio para formar íons arilnitrênios intermediários que sofrem N-substituição aromática intramolecular. A decomposição ácida de aril azidas é comparada com resultados de termólise tomados da literatura.We describe in this paper the action of trifluoroacetic acid, trifluoromethanesulfonic acid and aluminum chloride upon ortho-substituted aryl azides to form indoles, azepines and arylamines in good yields. The protonated azides lose nitrogen to form arylnitrenium ion intermediates which undergo intramolecular aromatic N-substitution. The acid decomposition of aryl azides is compared with reported thermolyses.

Organic Azides: An Exploding Diversity of a Unique Class of Compounds

“…This reaction was recently applied to the synthesis of complex indoles (Scheme ) 333–335. As an alternative to thermolysis or photolysis this cyclization can also be carried out by protonation or by the action of Lewis acids with the formation of electrophilic nitrenium ions (see also Section 4.6.3) 336…”

“…TFA) gives aryl or alkyl nitrenium ions that are analogous to carbocations 525–527. Aryl nitrenium ions are highly reactive intermediates, which react as electrophiles in either inter‐ or intramolecular336 reactions with aromatic groups (Scheme 135) 526. 528 The high reactivity is an argument for the carcinogenicity of such compounds 529…”

Organische Azide – explodierende Vielfalt bei einer einzigartigen Substanzklasse

“…Diese Reaktion hat in letzter Zeit verschiedene Anwendungen in der Synthese von zum Teil komplexen Indolen gefunden (Schema ) 333–335. Alternativ zur Thermolyse oder Photolyse kann diese Cyclisierung auch durch Protonierung oder Einwirkung von Lewis‐Säuren unter Bildung elektrophiler Nitrenium‐Ionen geführt werden (siehe auch Abschnitt 4.6.3) 336…”

A Novel and highly selective conversion of alcohols, thiols, and silyl ethers to azides using the 2,4,6-trichloro[1,3,5]triazine/n-Bu4NN3 system

“…33 and acyl azides. 34 In order to optimize the reaction conditions, at first the effect of different molar ratios of ROH/TT/n-Bu 4 our optimized conditions for the conversion of structurally different alcohols into their corresponding alkyl azides with 100% conversion (substrate consumption) which determined by GC. The results are shown in Table 1.…”

“…[2][3][4] Aliphatic azides are usually prepared by nucleophilic substitution of the corresponding halides or sulfonates by azide ion. [5][6][7][8] Due to the advantageous and attractive strategy of the direct synthesis of azides from alcohols, some limited methods have been developed.…”