“…When the substrates 10a , e , 11a , and 12a , d were treated only with a slight excess (1.2 equiv) of DMD, both 1 H NMR analysis of the reaction mixture (Table ) and the yields of isolated materials (Table ) revealed a high proportion of sulfone and considerable amounts of unreacted sulfide; the expected sulfoxides were found only as minor products. A literature survey indicated that the sulfones of 1-thiochromones and 1-thioflavones are readily available by oxidation with hot H 2 O 2 in acetic acid, 3b,,,, hot peracetic acid, hot monoperoxyphthalic acid, or with H 2 O 2 in trifluoroacetic acid at room temperature . All attempts to synthesize the corresponding sulfoxides by using less oxidant and/or milder conditions failed in that only mixtures of sulfide, sulfoxides, and sulfones were obtained. 3a,, Indeed, the pure 1-thiochromone 1-oxide ( 13a ) 41 and 1-thioflavone 1-oxide ( 15a ) 15 can only be prepared by dehydrobromination of the respective 3-bromo-1-thiochroman-4-one derivatives.…”