52 mg (E)-ethyl 2-(1-oxo-4-(thiophen-2-ylsulfonylimino)-1,4-dihydronaphthalen-2-ylthio)acetate (8a) was dissolved in 2 ml THF, to which was added 2 ml aqueous solution containing 107 mg Na2S2O4. The resulting biphasic solution was stirred at r.t. for 1 h until it turned pale yellow. The mixture was diluted with ethyl acetate and washed with water and brine. Dried over Na2SO4, the organic solution was filtered and the filtrate was concentrated. The crude product was purified via flash column (EtOAc/Hexane) yielding 25.2 mg (58.7%) title compound, m.p.: 116-118° C.
