On the reaction of (vinylimino)phosphoranes and related compounds. Part 30. Short new synthesis of 5-azaazulene derivatives. Some comments on reactivities of (vinylimino)phosphoranes

Article abstract of DOI:10.1039/P19950001001

A short new synthesis of phenyl-substituted and annulated 5-azaazulene (cyclopentaazepine) derivatives 15-18 consist of the reaction of <(1-phenylvinyl)imino>- and benz-annulated <(cycloalkenyl)imino>phosphoranes 8-11 with 4-(dimethylaminomethylene)cyclopenta-1,3-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 (vinylimino)phosphoranes 12-14, which have no phenyl group at the α-position relative to the nitrogen atom, consist of a intramolecular aza-Wittig reaction or a substitution reaction of aldehyde 1 with phophoranes 12-14 and subsequent hydrolysis to afford 5-(aminomethylene)cyclopenta-1,3-dienecarbaldehyde 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 wellas on model compounds 8C-12C were performed to gain insight via a theoretical interpretation based upon frontier molecular orbital theory (FMO): the first 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.

Full text of DOI:10.1039/P19950001001

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