Keten. Part VIII. The Adducts of Dimethylketen with Substituted Cinnolines

Abstract

Dimethylketen forms two types of adduct with cinnolines, both having oxadiazinocinnolinone structures. Cinnolines with no substituent in the 3 position form exclusively the [1,3,4]oxadiazino[4,3-a]cinnolinones (I) resulting from nucleophilic attack on the keten by N-2. 3-Alkylcinnolines form predominantly the [1,3,4]oxadiazino[3,4-a]cinnolinones (II) arising from nucleophilic attack by N-1. Hydrolysis of these adducts gives the normal amido-acids, which form different series of lactones with electrophiles. An unusual N-1 de-alkylation of a substituted tetrahydrocinnoline by polyphosphoric acid has been observed.