Retro‐ene reaction. II. Reaction of 4,5‐dichloro‐1‐hydroxy‐methylpyridazin‐6‐one with alkyl halides and carboxylic acid chlorides

Abstract

1‐Alkyl‐4,5‐dichloropyridazin‐6‐oncs and (4,5‐dichloro‐6‐oxopyridazin‐1‐yl)methylcarboxylates were synthesized from 4,5‐dichloro‐1‐hydroxymethylpyridazin‐6‐one and the corresponding alkyl halides or carboxylic acid chlorides. Also the reaction mechanisms via a fragmentation of retro‐ene type are discussed.

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.…”