6-Phenyl-5-azaazulene

Phenanthrene o-quinodimethane, 55 Phenyl-2-aza-l,3-pentadiene, 258 6-Phenyl-5-azaazulene, 260... 

Cyclization of 8-hydrazinO 3-phenyl-l-azaazulenes 69 with triethyl orthoformate gave 4,5-triazabenz[c(f]azulene derivative 70 which was easily hydrolyzed on silica gel and gave (2-chloro-8-imino-3-phenyl-l-aza-l,8-dihydoazulen-l-yl) formaldehyde oxime (87H767) (Scheme 17). 

Cycloaddition reactions have been carried out with corresponding bases of Vilsmeier salts of pyrroles. Thus reaction of 153 with dimethyl acetylenedicar-boxylate gave pyrrolizines 154 and 3a-azaazulenes 155 in a nonsynchronous reaction. The structure of 3H-pyrrolizine 154a was proved by X-ray analysis.96 In a closely related reaction, pyrrolizinones 156 and 157 were obtained from the corresponding Vilsmeier salts with phenyl isocyanate.97 Reaction of 2-p-nitrobenzoylindolin-3-one (158) with methyl acetoacetate gave the benzopyrrolizinone (159).5 7... 

Following on from a preliminary report <9lT(.6727>, Nitta and co-workers have published details of the formation of a number of 5-azaazulenes by the reaction of cyclopentadienyl aldehydes with vinylphosphoranes, the simplest product being the phenyl derivative, 3-phenylcyclohepta[c]azepine <95JCS(Pl )iooi>. 

Cycloaddition reactions have been carried out with Vilsmeier bases of pyrroles. Thus reaction of (180) with dimethylacetylene dicarboxylate gave pyrrolizines (181) and 3a-azaazulenes (182) in a non-concerted reaction <74JHC811>. In a closely related reaction, (183) was obtained from the Vilsmeier base with phenyl isocyanate <76H(4)i28i>. 

The intramolecular aza-Wittig reaction has been described previously as a convenient route for the synthesis of azepines, and, in a bimolecular equivalent, the reaction of 2-formyl-6-dimethyl-aminofulvene with phenyl-substituted vinyliminophosphoranes in a one-pot reaction offers a facile synthesis of phenyl-substituted 5-azaazulene (201) <91TL6727>. 

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