SynthesisofSomeNovelThioxanthenone-FusedAzacrownEthers,andTheir UseasNewCatalystsintheEfficient,Mild,andRegioselectiveConversionof Epoxides to b-Hydroxy Thiocyanates with Ammonium Thiocyanate by Hashem Sharghi*, Alireza Salimi Beni,and Reza Khalifeh Chemistry Department, College of Sciences, Shiraz University, Shiraz 71454, I.R. Iran (phone:00987112284822;fax:00987112280926;e-mail:shashem@chem.susc.ac.ir) The regioselective ring-opening reactions of some epoxides with ammonium thiocyanate in the presenceofaseriesofnew9H-thioxanthen-9-one-fusedazacrownethers, i.e. , 7 – 11 ( Scheme 1),andalso ofdibenzo[18]crown-6(12), Kryptofix $ 22 (13),andbenzo[15]crown-5(14)werestudied( Tables 1 and 2).TheepoxidesweresubjectedtocleavagebyNH 4 SCN in the presence of these catalysts under mild conditions in various aprotic solvents. Reagents and conditions were identified for the synthesis of individual b-hydroxythiocyanatesinhighyieldandwithmorethan90%regioselectivity.Theresultscan bediscussedintermsofafour-stepmechanism( Scheme 2): 1)formationofacomplexbetweencatalyst andNH 4 SCN, 2)releaseofSCN  fromthecomplex, 3)reactionofthereleasedSCN  atthestericallyless hinderedsiteoftheepoxide,and 4)regenerationofthecatalyst.Themajoradvantagesofthismethodare the high regioselectivity, the simple regeneration of the catalyst, the reuse of it through several cycles withoutadecreaseofactivity,andtheeaseofworkupofthereactionmixtures. Introduction. – Epoxides are one of the most versatile intermediates in organic synthesis, and a large variety of reagents are known for the ring opening of these compounds [1]. Their electrophilic reaction with different nucleophiles has been a permanentsubjectinorganicsynthesis[2–7].Amongthesenucleophiles,thereaction ofthethiocyanateionwithepoxides,intheabsenceorinthepresenceofacatalyst,isa widely studied and suitable method for the preparation of thiiranes [8–15]. The formation of thiiranes from the reaction of epoxides and thiocyanate ions has been proposed to occur through the intermediacy of the corresponding b-hydroxy thiocyanate, but this intermediate has not been isolated due to its rapid conversion to the corresponding thiirane [13–17]. There are two methods reported in the literatureforthesynthesisof b-hydroxythiocyanates.Inonemethod,thiocyanohydrins arepreparedbyopeningofacyclicsulfatewithNH 4 SCNtoformthecorresponding b- sulfate,whichisthenhydrolyzedtothethiocyanohydrines.Asecondmethodemploys the addition of thiocyanic acid, generated in situ at low temperature, to the epoxide [18–21]. It has been reported for these syntheses that the presence of some hydroquinone (¼ benzene-1,4-diol) or DDQ (¼ 4,5-dichloro-3,6-dioxocyclohexa-1,4- diene-1,2-dicarbonitrile) is required to stabilize the produced b-hydroxy thiocyanate and to inhibit its conversion to thiirane [16][22]. Although the reagents such as Ti(O i Pr) 4 [23], Ph 3 P·(SCN) 2 [24], TiCl 3 (or ZnCl 2 ) [25], and [Pd(PPh 3 ) 4 ] [26] are Helvetica Chimica Acta –Vol.90(2007) 1373 #2007VerlagHelveticaChimicaActaAG,Zürich