A route to fluorocontaining N,S-heterocycles via octafluoro-2,3-epoxybutane

Abstract The reaction of octafluoro-2,3-epoxybutane 1 with 2-aminothiophenol gave three kinds of novel fluorocontaining N , S -heterocyclic compounds depending on the solvent nature: 2,3-bis(trifluoromethyl)-3,4-dihydro-2 H -1,4-benzothiazin-2-ol 2 , 2-trifluoromethyl-2-[1-(2-aminophenylthio)-2,2,2-trifluoroethyl]-1,3-benzothiazolidine 6 and 5a,11a-bis(trifluoromethyl)-5a,6,11a,12-tetrahydro-5,11-dithia-6,12-diazanaphthacene 5 . Use of the toluene, dioxane, tetrahydrofuran, acetonitrile and dimethoxyethane gave the unexpected dihydrobenzothiazine 2 ( RS , SR  >  RR , SS ) in good to moderate yields. In dimethylsulfoxide and N , N -dimethylacetamide, unusual cyclization occurred resulting in benzothiazolidine 6 ( RS , SR / RR , SS  ∼ 1:1) in moderate yields. Formation of minor 1,1,1,3,4,4,4-heptafluoro-3-(2-aminophenylthio)-2,2-dihydroxybutane 4 which was converted into bis(benzothiazine) 5 was observed in all solvents tested with the exception of toluene and dioxane. The molecular structure of the RS , SR -diastereomer of dihydrobenzothiazine 2 , bis(benzothiazine) 5 and the RS , SR -diastereomer of benzothiazolidine 6 has been established by X-ray crystallography.