(2S,7R,11S, 16R)-1,8,10,17-tetraazapentacyclo [8.8.1.18,17.02,7.011,16] icosane and its enantiomer.: Synthesis, NMR analysis and X-ray crystal structure

(2S,7R, 11S, 16R)-1,8,10,17-tetraazapentacyclo[8.8.1.1(8.17).0(2,7).0(11,16)]icosane (7) has been synthesized by reaction of commercial 1,2-cyclohexanediamine with formaldehyde in dimethylformamide solution. The crystal structure of 7 has been determined by single crystal X-ray diffraction analysis. The crystal structure of 7 shows that the geometry of the N-atoms is the less likely cis-configuration, the precise configuration that was claimed by previous investigators to be unlikely to exist! The C-C-C bond angles within the cyclohexane rings of 7 are in the range 113.9(7)-124.6(8)degrees, indicating that the cyclohexane rings are more planar than chair-like. The N-C-N bond angles around the bridging methylene groups are similarly distorted from tetrahedral geometry. The crystal structure of 7 is compared with the previously reported structures of 1,3,6,8-tetraazatricyclo[4.4.1.1(3,8)]dodecane(l) and 1,4-dimethano-dibenzo[d,i]-1,3,6,8-tetrazecine(2). The title compound (7) {C16H28N4}, crystallizes in the orthorhombic, space group Fdd2, with lattice constants: a=11.9733(17) angstrom(3), b = 12.8485(18) angstrom, c = 19.095(3) angstrom, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, V= 2937.5(7)angstrom(3) Z= 8, D-c = 1.250 mg m(-3), F(000) = 1216, R-1 = 0.0834, wR(2)=0.2255. (c) 2005 Elsevier B.V. All rights reserved.