Aryl 1,5-dithia-2,4,6,8-tetrazocines. A synthetic, electrochemical, and structural investigation

Abstract

New preparative routes to the title compounds are reported in which the yields are substantially improved over previous methods. In one method, reaction of O 2 with a mixture of XC 6 H 4 CN 2 S 2 + Cl − and Ph 3 Sb leads to the products in 40–60% yield. In another, the reaction of the same salts with silylated amidines XC 6 H 4 C{NSiMe 3 }N(SiMe 3 ) 2 in a 1:1 mol ratio leads to the same compounds in 18–65% yield. The syntheses of 3,7-(XC 6 H 4 ) 2 {CN 2 S 2 N 2 C}, X = H, 4-CH 3 , 4-CH 3 O, 4-Cl, 4-CF 3 , and 3-CF 3 , are reported. Mixed derivatives were also prepared, but not isolated as pure compounds. The crystal structure of the 4-CF 3 compound has been determined by X-ray diffraction; triclinic, [Formula: see text] with Z = 1; cell dimensions: a = 6.835(2), b = 9.936(3), c = 6.320(2) Å, α = 96.44(3)°, β = 102.88(3)°, γ = 88.42(3)°. R = 3.4%, R w = 3.5% for 1100 data. The eight-membered ring is flat with equivalent bond lengths between any two types of atoms, indicative of a delocalized electron distribution. The 10π central aromatic rings have been oxidized and reduced in CH 2 Cl 2 using voltammetric methods. The reversible one-electron reduction step gives stable 11π species. The resistance to oxidation of the title compounds is contrasted to the ease of oxidizing 3,7-[(CH 3 ) 2 N] 2 {CN 2 S 2 N 2 C}, in accordance with earlier chemical studies.