Synthesis and Antinociceptive Activity of Substituted Derivatives of Potassium 1-Cyano-3-{(3-cyano-4,5,6,7-tetrahydrobenzo-[b]thiophen-2-yl)amino}-5-oxopenta-1,3-dien-2-olates

А series of new substituted potassium 1-cyano-3-{(3-cyano-4,5,6,7-tetrahydrobenzo[ b ]thiophen-2-yl)amino}-5-oxopenta-1,3-dien-2-olates was synthesised by the ring opening reaction of substituted 2-{[2-oxo-5-arylfuran-3(2 H )-ylidene]amino}-4,5,6,7-tetrahydrobenzo[ b ]thiophene-3-carbonitriles under the action of cyanoacetic acid derivatives and potassium tert -butoxide. Antinociceptive activity and acute toxicity of the obtained compounds were investigated by in vivo experiments. It was found that the obtained substituted potassium salts possess pronounced antinociceptive activity and are practically non-toxic drugs.