Serhii A. Siryi, V. Timoshenko, Y. Vlasenko
Aug 19, 2015
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Journal
Chemistry of Heterocyclic Compounds
Abstract
The first representatives of the novel 4,7а-dihydro-3аН-thiopyrano[3,4-d]isoxazole heterocyclic system, containing an ester, carboxyl, or hydroxymethyl group at position 3 and a trifluoromethyl group at position 6 were obtained by [3+2] cycloaddition reaction of ethyl cyanocarboxylate N-oxide and 6-trifluoromethyl-2Н-thiopyran, followed by further transformations of the ethyl 6-trifluoromethyl-4,7а-dihydro-3аН-thiopyrano[3,4-d]isoxazole-3-carboxylate intermediate. The cleavage of the isoxazoline ring of the obtained compounds led to the formation of 6-trifluoromethyl-2Н-thiopyran derivatives with nitrile or carbonyl-containing functionality at position 3. Transformations of the thiopyran moiety in 4,7а-dihydro-3аН-thiopyrano[3,4-d]isoxazole were studied for the case of Pummerer reaction product with oxidized sulfur atom, ethyl 6-trifluoromethyl-4,7а-dihydro-3аН-thiopyrano[3,4-d]isoxazole-3-carboxylate 5-oxide, which was converted to ethyl 6-trifluoromethyl-4Н-thiopyrano[3,4-d]isoxazole-3-carboxylate.