Optically active cyclic diaryl(alkoxy)sulfonium salts with intramolecular S center dot center dot center dot O interaction: synthesis, absolute configuration and stereoselective hydrolysis

Optically active cyclic sulfonium salts {(S)-(-)-1-[2'-(methoxycarbonyl)phe nyl]-3H-2,1-benzoxathiol-1-ium tetrafluoroborate (S)-(-)-2, (R)-(-)-1-[8'-( methoxycarbonyl)-1'-naphthyl]-3H-2,1-benzoxathiol-1-ium tetrafluoroborate ( R)-(-)-4 and (R)-(-)-1-[2'-(methoxycarbonyl)phenyl]-3H-2,1-naphtho[1,8-d,e] -oxathiin-1-ium tetrafluoroborate (R)-(-)-6} were prepared from optically a ctive diaryl (acyloxy)(alkoxy)spiro-lambda(4)-sulfanes (R)-(+)-1, (S)-(-)-3 and (S)-(+)-5, respectively. The molecular structures determined by H-1 an d C-13 NMR measurements can be described with spiro-lambda(4)-sulfane-like trigonal bipyramidal geometry about the central sulfur owing to the SO(carb onyl) intramolecular interaction in the axial position. The stereochemistry of the hydrolysis reactions of sulfonium salts 2, 4, 6 and spiro-lambda(4) -sulfanes 1, 3, 5 depending on pH is discussed in detail. (C) 2000 Elsevier Science Ltd. All rights reserved.