Cyclization of 1-(2-hydroxyphenyl)-3-phenylpropane-1,3-dione with isothiocyanates: a simple one-pot synthesis of novel 4-oxo-2-phenyl-4H-chromene-3-carbothioamides and 2-phenyl-3-(2-thioxo-2H-1,3,5,4-thiadiazaphosphinin-6-yl)-4-oxo-4H-chromenes

A simple synthetic strategy to construction of novel 4-oxo-2-phenyl-4H-chromene-3-carbothioamides (2–6) was achieved. The synthetic strategy depended on the treatment of 1-(2-hydroxyphenyl)-3-phenylpropane-1,3-dione (1) with some examples of aryl, aralkyl, aroyl and phosphorus isothiocyanates with promotion of DBU. The interesting 4,6-diphenyl-5-(2-hydroxy-benzoyl)-2-thioxo-3,4-dihydro-2H-1,3,4-oxazaphosphinine (8) as a highly regioselective product was obtained through treatment of the substrate 1 with phenyl phosphonisothiocyanatidous chloride whereas the other novel 2-phenyl-3-(2-thioxo-2H-1,3,5,4-thiadiazaphosphinin-6-yl)-4-oxo-4H-chromenes (9 and 10) were formed by using phosphorous diisothiocyanate and triisothiocyanate, respectively, under the same basic reaction conditions. All the reaction mechanisms were discussed. Structures of all the synthesized products were established by elemental analysis and available spectral tools.