Abstract
The reaction of azulene (1) with a 0.4- 0.5 molar amounts of a heterocyclic aldehyde (i.e., furaldehyde, thiophene-2-carbaldehyde, pyrrole-2-carbaldehyde and imidazole-2-carbaldehyde) in acetic acid at room temperature (25 °C) for 1-8 h under argon gave the corresponding 1, 1'-methylenediazulene having a heterocyclic substituent at C-a position (2, 23.0% yield; 3, 49.8%; 4, 2.3%; 5, 70.6%, respectively). The structures of these products were established on the basis of their spectro scopic (UV/VIS, 1H-NMR and EI-MS) data.
