Flavonoids. V. Thiation of Isoflavones

3-(2-Chloro-4-hydroxyphenyl)-1-thioisocoumarin

“…Although more than 200 isocoumarins have been isolated, 1-thioisocoumarins are hitherto unknown in nature. The thio-analogues of a number of related natural products (Levai, 1992;Dudley et al, 1967;Baruah et al, 1988;Kumar et al, 2005;Levai, 1999) have been reported. However, reports of synthetic 1-thioisocoumarins are rare (Duddeck & Kaiser, 1985).…”

Synthesis of some 3‐aryl‐1H‐isochromene‐1‐thiones

“…Although, more than two hundred isocoumarins and dihydroisocoumarins have been isolated and the number is still increasing dramatically, 1-thioisocoumarins are thus far unknown in nature. A review of literature reveals that while, the thio analogues of a number of associated natural products viz., chromones, [11] flavones, [12] isoflavones [13] and coumarins [14] have been prepared; the reports of synthetic 1-thioisocoumarins (1H-isochromene-1-thiones) are exceptional [15]. The various reagents and conditions employed for thionation include phosphorus pentasulfide in presence of base [16], hydrogen sulfide in the presence of acid [17], bis-(tricyclohexyltin)sulfide with boron trichloride [18] bis(trimethyl-silyl)sulfide with hydrated cobalt chloride [19] and boron sulfide in refluxing chloroform [20].…”