Azulenopyrroles

The ratio between the values of the TRE or between those of the HSRE for the isomer pairs (88)-(93) is analogous to that between the values of the CCMRE (given in eV under the structural formulae) for the positional isomers of azulenofurans, azulenopyrroles, and azulenothiophenes (87H2025). 

Pyrroles. The action of liquid ammonia upon furan 164 initiates heteroatom exchange to afford azulenopyrroles 194 and (after degradation) 195 (61CIL1715). 

Azaazulenes are versatile precursors in syntheses of peri-fused azulenopyrrole derivatives in the course of the [8+2] cycloaddition by means of electron-deficient acetylenes or of acetylene equivalents (Schemes 45 and 46). Treatment of l-aza-2-azulenones 196a and 196b... 

Whereas bicyclic azulenes suffer thermal isomerization to )tield naphthalene derivatives (52CRV127, p. 169 85HOU(5/2c)127, p. 413), there are a few examples of transforming an azulene-fused heterocyclus to another heteroring or of rearranging it to benzene. The formation of azulenopyrrole 194 from azulenofuran 164 (61CIL1715) was mentioned previously (Section 2.4.1.6). 

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