Ethyl Acetoacetate → ethyl 6,7-dihydro-4-methyl-2-(4-chlorphenyl)-4H-pyrano[4,3-d]thiazole-4-acetate

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Reaction Steps

A mixture of the starting material of formula II, 2-(4-chlorophenyl)-4-(β-hydroxyethyl)thiazole (24.0 g, 0.1 mole, described in Example 1), ethyl acetoacetate (19.5 g, 0.15 mole) and p-toluenesulfonic acid hydrate (38.0 g, 0.2 mole) in toluene (1000 ml) is heated at reflux temperature, with water separation, for 20 hr. The mixture is evaporated under reduced pressure and the residue is triturated with petroleum ether. The residue is dissolved in a mixture of aqueous sodium bicarbonate solution and ether. The organic solution is separated, washed with saturated sodium chloride solution, dried over sodium sulfate and evaporated under reduced pressure to give ethyl 6,7-dihydro-4-methyl-2-(4-chlorphenyl)-4H-pyrano[4,3-d]thiazole-4-acetate (IV, R1 = Cl, R2 = CH3, A= COOCH2CH3 and n= 1).

Provenance & Evidence