2-Fluorobenzoyl chloride → 3-Chloro-6-(o-fluorobenzoyl)-5,6,7,8-tetrahydro-4-methylpyrido[4,3-c]pyridazine

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Reaction Steps

A suspension of 14.4 g of 6-carbethoxy-5,6,7,8-tetrahydro-4-methyl-3(2H)pyrido[4,3-c]pyridazinone in 100 cc of concentrated hydrochloric acid is heated to the boil at reflux for 20 hours while stirring. The resulting 5,6,7,8-tetrahydro-4-methyl-3(2H)pyrido[4,3-c]pyridazinone is isolated (M.P. of the hydrochloride 344° to 348°) and is converted in a manner analogous to that described in Example 1(e) into 3-chloro-5,6,7,8-tetrahydro-4-methylpyrido[4,3-c]pyridazine (M.P. of the maleate: 170° to 173°), this is reacted with o-fluorobenzoyl chloride, whereby 3-chloro-6-(o-fluorobenzoyl)-5,6,7,8-tetrahydro-4-methylpyrido[4,3-c]pyridazine is obtained (M.P. 151°-153°).

Provenance & Evidence