Synthesis of isomerically pure 3-(5-trifluoromethyl-1,2,3-triazol-4-yl)cinnamic acid derivatives via the reaction of 4-aryl-6-trifluoromethyl-2-pyrones with sodium azide

Treatment of 4-aryl-6-trifluoromethyl-2-pyrones with sodium azide in DMSO afforded the corresponding (Z)-3-(5-trifluoromethyl-1,2,3-triazol-4-yl)cinnamic acids in good yields. Similarly, 4-aryl-3-carbethoxy-6-trifluoromethyl-2-pyrones smoothly reacted with sodium azide in acetonitrile to produce (E)-2-ethoxycarbonyl-3-(5-trifluoromethyl-1,2,3-triazol-4-yl)cinnamic acids in high yields, whereas their reactions in ethanol, accompanied by a configurational change, gave the thermodynamically more stable (Z)-2-ethoxycarbonyl-3-(5-trifluoromethyl-1,2,3-triazol-4-yl)cinnamic acids.