STUDIES ON METHOXYLATION IN THE 7H-NAPHTHO[1,2,3-I,J][2,7]NAPHTHYRIDIN-7-ONE SYSTEM

Studies on methoxylation in the 7H-naphtho[1,2,3-i,j][2,7]naphthyridin -7-one (sampangine) system represented by 3-bromo- and 4-bromosampangi ne as well as sampangine itself are described. We have found that regi oselectivity of nucleophilic substitution in the sampangine system can be directed by reaction conditions. Under kinetic control (lower temp eratures) substitution at C-4 is the predominant reaction, regardless of whether S-bromo or 4-bromosampangine were used. At higher temperatu res, when the reaction is thermodynamically controlled, substitution o f the bromine atom at C-3 predominates. This is the first reported exa mple of nucleophilic substitution in ring A of the 7H-naphtho[1,2,3-i, j][2,7]naphthyridin-7-one system.