POLYAZA HETEROCYCLES .3. HALOGENATION OF 1-SUBSTITUTED QUINOXALINO[2,3-C]CINNOLINES - MECHANISTIC IMPLICATIONS

Since it has been proposed that halogenation of quinoxalino[2,3-c] cin nolines at C-10, using hydrogen chloride or bromide in chloroform, occ urs through initial protonation of the substrate at N-12, attempts hav e been made to inhibit this protonation by the introduction of an addi tional substituent at C-l, Where this substituent is chloro, bromo or methyl, chlorination still occurs preferentially at C-10, although the yield and the reaction decrease along the series, lending weight to t he mechanistic proposal.