Cyclophanes with Sharp Corners:  Synthesis of Macrocycles Containing One or Two 1,5,2,4,6,8-Dithiatetrazocine Rings

Several cyclophanes have been prepared which contain one or two of the bent 3,7-diamino-1,5,2,4,6,8-dithiatetrazocine (DTTA) ring systems linked by polymethylene chains:  1,8-dimethyl-1,8-diaza[8](3,7)(1,5,2,4,6,8-dithiatetrazocinophane) (6), 1,6,15,20-tetramethyl-1,6,15,20-tetraaza[6.6](3,7)(1,5,2,4,6,8-dithiatetrazocinophane) (8), and 1,5,14,18-tetramethyl-1,5,14,18-tetraaza[5.5](3,7)(1,5,2,4,6,8-dithiatetrazocinophane) (9). In each synthesis, an N,N‘-dimethyl-α,ω-diamine was converted to the corresponding bis(guanidinium hydrobromide), which was then treated with sulfur dichloride in the presence of DBU under conditions of moderate dilution to form the cyclophane in low yield (0.1−0.7%). When N,N‘-dimethylhexanediamine was used, a cyclophane containing a single DTTA ring bridged by the polymethylene chain was formed (6), but with the corresponding butane- and propanediamines, dimeric cyclophanes containing a pair of DTTA rings resulted (8 and 9). When N,N‘-dimethylpentanediamine was used, a monomeric phane, 1,7-dimethyl-1,7-diaza[7](3,7)(1,5,2,4,6,8-dithiatetrazocinophane) (7), appeared to be formed, but it was not isolated as a pure material. Compounds 6, 8, and 9 were characterized by X-ray crystallography. Crystallographic data:  for 6, C₁₀H₁₈N₆S₂, monoclinic P2₁/c, Z = 4, a = 8.356(1) Å, b = 12.991(2) Å, c = 13.298(2) Å, β = 111.705(9)°; for 8, C₁₆H₂₈N₁₂S₄·0.69CH₂Cl₂, triclinic, P1̄, Z = 2, a = 9.6095(8) Å, b = 11.7085(11) Å, c = 13.2683(10) Å, α = 66.243(7)°, β = 82.340(6)°, γ = 73.989(7)°; for 9, C₁₄H₂₄N₁₂S₄, triclinic P1̄, Z = 2, a = 6.304(1) Å, b = 8.366(1) Å, c = 21.357(3) Å, α = 91.03(1)°, β = 92.26(1)°, γ = 110.56(1)°. The dimeric cyclophanes 8 and 9 were observed to form roughly rectangular troughs enclosing a small cavity, with the DTTA rings at two of the corners. The DTTA ring of the monomeric phane 6 was observed to be significantly distorted when compared with the structures of less constrained DTTA's, and ab initio calculations indicated that the phane 7, which has a shorter bridge, but for which there is no X-ray structure, is even more highly strained.