Novel synthesis modes and properties of [1,4]benzodioxinopyridazines |
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Authors: | John P Chupp Claude R Jones Maria L Dahl |
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Abstract: | A simple synthesis involving fusion of catechol and derivatives with 3,4,5-trichloropyridazine has furnished 4-chloro1,4]benzodioxino2,3-c]pyridazines 5 for the first time. This new method complements the previously reported base promoted procedure for preparing 4-chloro1,4]benzodioxino-2,3-d]pyridazines 3 . Employing both methods, 4-(trifluoromethyl)catechol was converted to the four regio isomers 3b,c and 5c,d . Structure assignment of these four was aided by the remarkably consistent influence of the pyridazine 4-chlorine substituent and diazo-linkage in inducing 1H nmr downfield shifts of their nearest neighbor phenyl ring protons. Finally, contrary to what might be expected from previously reported results, reaction of methoxide with either 3 or 5 , gave chlorine substitution with formation of methoxybenzodioxinopyridazines 6 and 7 respectively. However, these reactions both give what appears to be an unprecedented rearrangement, with conversion of 2,3-c]-pyridazine to 2,3-d]pyridazine, and vice versa. |
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