Optimized synthesis of Di, Tri and tetrafused pyridazinium cations

By combining two complementary statistical techniques (fractional factorial experimental design and simplex operation) the synthesis of the parent pyr ido[1,2-b]-pyridazinium cation has been successfully carried out (the yield was improved from less than 10 to 65%) by basic condensation of 2-methyl-1 -aminopyridinium mesitylenesulfonate and [1,4]dioxane-2,3-diol, Using the o ptimized reaction conditions, other related heterocyclic cations could be p repared, and two interesting examples are now reported. (C) 2000 Elsevier S cience Ltd. All rights reserved.