Aromatic azides, annulation with

Scheme 39 shows a formal [3 + 3] annulation of aromatic azides 112 with aromatic imines proceeding through a cascade process of Rh(III)-cata-lyzed amination followed by an intramolecular electrophilic aromatic substitution and aromatization to prepare the acridines 113 and can be classified as a type B ring closure. The reaction can be performed starting from aldehydes 111 which form imines in situ, and these direct the CH amination. Benzyl-amine proved to be the best amine, and magnesium sulfate was appHed as a water scavenger. The substrate scope was examined, which is in part shown in Scheme 39 (2013JA12548). 

EUman and collaborators devised a method for the preparation of unsymmetrical, bis-substituted phenazines 137 via a [3 + 3] annulation of aromatic azides and unsymmetrical azobenzenes, involving a rhodium(III)-catalyzed amination, subsequent intramolecular electrophilic aromatic substitution, and aromatization (Scheme 67) (13JA12548). On the azobenzenes, a variety of functional groups in different positions are tolerated. With meta-substituted azobenzenes, amination occurred at the least sterically hindered site, furnishing only one isomer. Electron-donating substituents on the azobenzenes, however, resulted in markedly lower yields. The amination proceeded well with both neutral and electron-poor aromatic azides with varying substitution patterns. The authors proposed the mechanism shown in Scheme 67. 

Ellman and coworkers reported a new [3+3] annulation reaction for the preparation of acridines and phenazines by Rh(III)-catalyzed C-H amination of aromatic imines and azobenzenes with aromatic azides. The reaction mechanism proceeds by C-H activation followed by intramolecular electrophilic aromatic substitution and aromatization to offer the respective products. Equations (5.81)-(5.83) illustrate that a broad range of acridines and phenazines can be generated with diverse functionality [44]. 

The cyclopentene annulations can also occur in the reactions of alkynyliodo-nium salts with nitrogen- and sulfur nucleophiles (Scheme 61). Specifically, azi-docyclopentene 155 is formed upon treatment of octynyliodonium tosylate 154 with sodium azide in dichloromethane [123]. The reaction of alkynyliodonium salt 156 with sodium toluenesulfinate results in the formation of substituted indene 157 via alkylidene carbene aromatic C-H bond insertion [124]. 

Cyclizations. Annulation accompanies oxidation of A-sulfonyl-4-methoxyanilines with Phl(OCOCp3)2 in the presence of 1-alkenes. 5-Methoxyindoles or indolines are produced in this one-pot reaction. Cyclization of 3-arylpropyl azides where the aromatic ring is activated (e.g., 3-methoxylated) to fused quinone imines is observed. ... 

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