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Thermal react ion of tri bu tyl ( i nden -3yl i m i no) p hosp hora ne with ~l,punsaturated ketones and a Ide hydes led to a Michael-type C-C bond formation and subsequent aza-Wittig reaction to give 5H-indeno(l,2b)pyridines in good to modest yield. The products were oxidized conveniently by chromium trioxide and t-butyl hydroperoxide to give 5H-indeno[l,2-b] pyridin-5-ones, including the 4-azafluorenone alkaloid onyc h i ne.

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A short new synthesis of phenyl-substituted and annulated 5-azaazulene (cyclopenta[c]azepine) derivatives 15-18 consists of the reaction of [( 1 -phenylvinyl)imino]-and benz-annulated [(cycloalkenyl)imino]phosphoranes 8-1 1 with 5-(dimethylaminomethylene)cyclopenta-l,3-dienecarbaldehyde 1 in an enamine alkylation (Michael addition) process, subsequent proton migration-ketonization, and condensation of the formyl group with the iminophosphorane moiety (aza-Wittig reaction). On the other hand, reactions of aldehyde 1 with (viny1imino)phosphoranes 12-14, which have no phenyl group at the or-position relative to the nitrogen atom, consist of a intramolecular aza-Wittig reaction or a substitution reaction of aldehyde 1 with phosphoranes 12-14 and subsequent hydrolysis to afford 5-(aminomethylene)cyclopenta-1,3dienecarbaldehyde 19 and its derivatives 20 and 21, respectively. In the context of selectivity observed in the reaction of phosphoranes 8-11 and 12-14 with aldehyde 1, respectively, MNDO calculations on compounds 1 and 12A, 12B as well as on model compounds 8C-12C were performed to gain insight via a theoretical interpretation based upon frontier molecular orbital theory (FMO): the former reaction, giving 5-azaazulene derivatives, would be an FMO-controlled reaction, while the latter is a charge-controlled reaction. Several spectral and chemical properties of heterocycles of 16-18 are analysed.

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