Synthesis, crystal, and molecular structures and conformations of naphthot[1,8-b,c]-1,5-dithiocin-1,1-dioxide,-1,5-dioxide,-1,1,5-trioxide and -1.1,5,5-Tetraoxide

Chemoselective oxidation of the known naphtho[1,8,-b,c-1,5-dithiocin, dithioether 1, to the corresponding -1,1-dioxide: monosulfone 3, 1,5-dioxide: cis-disulfoxide 4, or -1,1,5,5-tetraoxide: disulfone 6 can be accomplished with potassium permanganate and a phase transfer catalyst in a two phase system in 66% yield, with sodium metaperiodate in aqueous methanol in 95% yield, or ruthenium tetraoxide in 70% yield, respectively. Oxidation of the known monosulfoxide 2 with potassium permanganate and a phase transfer catalyst in a two phase system also gave monosulfone 3 in 73% yield. The corresponding -1,1,5-trioxide: sulfoxide-sulfone 5 was selectively prepared in quantitative yield by oxidation of the monosulfone 3 with sodium metaperiodate in aqueous methanol. The crystal and molecular structures, and conformations of naphtho[1,8-b,c]-1,5-dithiocin-1,1-dioxide (3), -1,5-dioxide (4), -1,1,5-trioxide (5), and -1,1,5,5-tetraoxide (6) were determined by single crystal X-ray analysis. These compounds crystallize in the monoclinic space group P2_1/c with a=13.184(4)Å, b=13.182(5)Å, c=7.106(l)Å, β=104.14(5)°, and Z=4, the orthorhombic space group P_bca, with a=17.931(2)Å, b=13.108(3)Å, c=20.280(4)Å, and Z=16, the monoclinic space group P2_1/n with a=9.298(1)Å, b=10.264 (2)Å, c=13.396(2)Å, β=110.06(1)°, and Z=4, and the orthorhombic space group P_bca with a=12.258(3)Å, b=9.997Å, C=20.168Å, and 2-8, respectively. The structures were solved by direct methods. Full-matrix least-squares refinement led to conventional R factors of 0.034, 0.046, 0.041, and 0.049, respectively. The conformations of the molecules in the solid state were distorted boat, boat with cis-dlequatorial sulfoxide; boat with equatorial sulfoxide, and the unusual twist conformer, respectively.