- 1,3-Dipolar cycloaddition of diazomethane to differently substituted 2-methylpyridazin-3(2H)-ones
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Cycloaddition of diazomethane to 4- or 5-substituted 2-methylpyridazin-3 (2H)-ones 1,2 occurs in a practically regiospecific manner to give the expected adducts, which are not stable enough to be isolated and under the reaction conditions are transformed into N, N′-dimethylpyrazolopyridazinones and/or 2,4 (or 2,5)-dimethylpyridazin-3(2H)-ones, depending on the nature and position of the substituents. The regiochemistry of the cycloaddition and the reactivity of pyridazin-3 (2H)-ones 1,2 have been accounted for theoretically by the FMO approach.
- Farina, Francisco,Martin, M.Victoria,Romanach, Magali,Sanchez, Felix
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p. 1431 - 1436
(2007/10/02)
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- PYRAZOLOPYRIDAZINONES BY 1,3-DIPOLAR CYCLOADDITION OF DIAZOMETHANE TO PYRIDAZIN-3(2H)-ONES
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N-methylpyridazin-3(2H)-ones 1-3 react slowly with diazomethane to give, as main products, the N,N'-dimethylpyrazolopyridazin-4(5H)-ones 10a and 10 b in a 1 : 2 ratio.The reaction of diazomethane with the N-methyl-4-bromopyridazin-3(2H)-one (4) leads to N1,N6-dimethylpyrazolopyridazin-7(6H)-one (9a).In the first case, the regioselectivity of the primary 1,3-dipolar cycloaddition is the reverse of that observed in enone systems.
- Farina, Francisco,Martin, M. Victoria,Sanchez, Felix,Tito, Amelia
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p. 175 - 178
(2007/10/02)
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