Formation and X-ray Structures of Eight- and Sixteen-Membered Rings (ArC)_nN_2n(SPh)_n[n= 2, Ar = 4-XC₆H₄(X = Br, CF₃);n= 4, Ar = 4-BrC₆H₄] and the Electronic Structures of (HC)₂N₄(SH)₂and (HC)₂N₄(SH)₂^2-

Abstract

Optimum yields of heterocyclic products are obtained when the reaction of 4-XC(6)H(4)CN(2)(SiMe(3))(3) (X = Br, CF(3)) with PhSCl in a 1:3 molar ratio in CH(2)Cl(2) is carried out at -100 degrees C followed by the mixture being warmed to -70 degrees C for 16 h. Under these conditions the eight-membered rings (4-XC(6)H(4))(2)C(2)N(4)S(2)Ph(2) (1b, X = Br; 1c, X = CF(3)) are obtained in 64 and 80% yields, respectively, in addition to the purple diazenes Z,E,Z-PhSN(4-XC(6)H(4))CN=NC(C(6)H(4)X-4)NSPh (2b, 8%; 2c, 19%) and, in the case of X = Br, the sixteen-membered ring (4-BrC(6)H(4))(4)C(4)N(8)S(4)Ph(4) (3) (8%). With a reaction time of 40 h the yield of 3 is increased to 25%. By contrast, the reaction of 3-BrC(6)H(4)CN(2)(SiMe(3))(3) with 3 equiv of PhSCl at -70 degrees C gives Z,E,Z-PhSN(3-BrC(6)H(4))CN=NC(3-BrC(6)H(4))NSPh in 75% yield. A possible pathway for the formation of cyclic products is proposed. The solid-state structures of 1b, 1c, and 3 were determined by X-ray crystallography. The eight-membered rings 1b and 1c adopt long boat conformations with the phenyl groups (attached to S) in equatorial positions. Density functional theory (DFT) calculations for the model ring system (HC)(2)N(4)(SH)(2) reveal that the observed C(2)(v)() geometry is the result of a second-order Jahn-Teller distortion of the planar (D(2)(h)()) structure. The chair conformer (C(2)(h)()) is only ca. 10 kJ mol(-)(1) higher in energy than the boat conformer. The hypothetical dianion (HC)(2)N(4)(SH)(2)(2)(-) is predicted to have a transannular S.S contact of about 2.5 Å. The sixteen-membered ring 3 has a cradle-like structure with S(4) symmetry.

On the selenepin/benzene selenide valence tautomerizations: electronic and steric effects at theoretical levels

“…This forecast can also be supported by the initiative that for small organic systems B3LYP method can give more reliable results than higher level ab initio methods [65][66][67][68][69]. In addition, density functional theory (DFT) calculations (1), where X = F, Cl, Br, CH 3 , OCH 3 , CF 3 , CN, and NH 2 ; Y = Me, Et, and i-Pr have been applied successfully to a number of problems in chalcogen-nitrogen chemistry [70][71][72][73][74].…”

Eight- and 16-Membered Cyanuric−Sulfanuric Ring Systems: C2N4S2 → C2N3S Ring Contraction

“…(Me 2 N) 2 C 2 N 4 S 2 (O) 2 [N(CF 3 ) 2 ] 2 ) . However, the boat is twisted compared to the C 2 N 4 S 2 ring in the corresponding S(IV) systems 1a and 1b , apparently in order to minimize steric interactions between the endo oxygen substituents attached to the sulfur atoms. A quantitative indication of the distortion of the boat conformation is provided by the comparison of the SNCN and NSNC torsion angles for 1b , 3b , and 3c given in Table , from which it can be seen that the distortions in 3b and 3c are quite disparate.…”

“…X-ray Structures of 2c, 4b, and 4c. The X-ray structure of the 16-membered ring 2a has been described previously . We have determined the structure of a second example of this macrocycle, 2c , to provide an appropriate comparison with structural parameters of the corresponding S(VI) system 4c .…”

“…The adduct LiN(SiMe 3 ) 2 · Et 2 O was then precipitated out of solution, washed with hexane, and stored in a drybox. The S(IV) heterocycles 1a − c , 2b , and 2d were prepared by the reaction of a trisilylated benzamidine with 3 equiv of an arene sulfenyl chloride at very low temperatures, as reported in the literature …”

“…Consequently, we turned our attention to eight-membered (CNSN) 2 rings. The S(IV) systems of type 1 and the related 16-membered rings 2 are obtained in reasonable yields by the reaction of trisilylated benzamidines with arene sulfenyl chlorides under kinetically controlled conditions …”