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We have worked out the optimal conditions for synthesis of 2,4-diaryl-5-oxo-5,6,7,8-tetrahydrochromenylium and -thiochromenylium salts based on triketones of the 2-(1,3-diaryl-3-oxopropyl)cyclohexane-1,3-dione series. For the first time, along with 5-oxo-substituted salts, we have obtained 5-thioxo-5,6,7,8-tetrahydrothiochromenylium salts. A necessary condition for the formation of the latter on treatment...