POLYAZA HETEROCYCLES .2. NUCLEOPHILIC-SUBSTITUTION OF HALOGENS IN HALOGENOQUINOXALINO[2,3-C]CINNOLINES

10-Chloroquinoxalino[2,3-c]cinnoline readily undergoes methoxydechlori nation when treated with sodium methoxide. The 1-, 2-, 3-, 4- and 9-ch loro isomers are unreactive towards this reagent but the 9,10-dichloro derivative undergoes substitution of both chlorines (the 10-position being much the more reactive). The 9- and 10-bromo analogues are both unreactive towards sodium methoxide, but the 9- and 10-fluoro analogue s are both highly reactive to the extent that it has not been possible even to isolate the 10-fluoro compound. Routes to 9 and 10-piperidino quinoxalino[2,3-c]-cinnolines are described.