Substituted 1,3,2,4-benzodithiadiazines and related compounds

Despite some limitations, the 1:1 condensation of n-RC6H4-N=S=N-SiMe3 (n = 2, 3 ,4; R = CH3 OCH3 F, Cl, CF3) with SCl2 followed by intramolecular elec trophilic ortho-cyclization, was found to be a general synthetic approach t o the corresponding 5-R, 6-R, and 7-R-substituted 1,3,2,4-benzodithiadiazin es, formally antiaromatic 12 pi-electron compounds. For precursors with n = 3, the high regioselectivity of the cyclization resulted in exclusive (R = OCH3, F) or predominant (R = CH3 Cl) formation of 6-R isomers; the ratio o f the major 6-R isomer to the minor 8-R one was found to be 72:28 (R = CH3) or 78:22 (R = Cl). The preferred direction of cyclization is consistent wi th thermodynamics of the corresponding intermediate sigma-complexes as well as factors of kinetic control for an orbital-controlled El-Nu reaction. Ac cording to the X-ray diffraction data, the molecules of 5-CF3 (15) and 6-F (12) derivatives are nearly planar, while the molecules of 5-OCH3 (7) and 6 -CH3 (4) derivatives are bent along the S-1... N-4 line by similar to 11 de grees (7) or 7 degrees (4). An attempt to adopt CsF-induced intramolecular nucleophilic ortho-cyclization of Ar-F-S-N=S=N-SiMe3, into polyfluorinated 1,3,2,4-benzodithiadiazines for polyfluroropyridine derivatives resulted in formation of polyfluorinated aminopyridines. Data obtained ave consistent with a previously suggested scheme of sulfur-nitrogen chain shortening duri ng cyclization. Mild acid hydrolysis of the title compounds was shown to be a convenient synthetic route to substituted 2,2'-diaminodiphenyl disulfide s (including polyfluorinated ones) via the corresponding 2-aminobenzenethio ls. (C) 1999 John Wiley & Sons, Inc.