Retro‐ene reactions. III. Alkylation of 4,5‐dichloro‐1‐hydroxymethylpyridazin‐6‐ones: Synthesis of 4,5‐dichloro‐1‐(ω‐phthalimido and saccharin‐2′‐ylalkyl)pyridazin‐6‐ones

Abstract

4,5‐Dichloro‐1‐(ω‐phthalimido and saccharinyl‐2′‐ylalkyl)pyridazin‐6‐ones were synthesized from 4,5‐dichloro‐1‐hydroxymethylpyridazin‐6‐one and the corresponding N‐(ω‐haloalkyl)phthalimides and saccharins via a fragmentation of retro‐ene type.

Arenesulfonylheterocycles (I): Synthesis and reactions of 2‐benzenesulfonyl‐4,5‐dichloropyridazin‐3‐ones with amines

“…The results of the sulfonylation for 1 under our condition are different from the sulfonylation of 2-pyridone [2], whereas Jan-Feb 2002 203 Kim and Y.-J. Yoon that is similar to the alkylation of 1 with alkyl halides in the presence of potassium carbonate [4,7]. According to Kim,et al [4], potassium ion in the potassium salt of 1 may be located in the proximity of oxygen because the electron density on oxygen of the carbonyl group is higher than that of nitrogen, at the 2-position in a free anion of 1.…”

Recent Progress in the Chemistry of Pyridazinones for Functional Group Transformations

“…Regioselective functionalization of 4,5-dichloropyridazin-3­(2 H )-one is directly achieved in polar solvents such as H 2 O, THF, MeOH, and mixed solvents of these in excellent yields . On the other hand, 2-hydroxy, − 2-oxopropyl, 1,1-dibromo-2-oxopropyl, , 1-bromo-2-oxopropyl, and 2-acetyloxymethyl-4,5-dichloropyridazin-3­(2 H )-one , undergo easily the retro-ene reaction by heating and/or in the presence of base. The value of p K a is a great guide to the leaving group ability.…”