Synthesis and conformation analysis of cis-1,2-disubstituted cyclododecanes

cis-1,2-Disubstituted cyclododecanes 2 were synthesized by sodium borohydride reduction of 2-monosubstituted cyclododecanones and their structures were confirmed by H-1-NMR, C-13 NMR and elemental analysis. The higher cis-selectivity of NaBH4 reduction of 2-monosubstituted cyclododecanones was rationalized by the mode of "corner position carbonyl participation". Crystal data for 2c: M-r = 263.21, monoclinic, space group P2(1)/c, a = 1.11140(7), b = 2.62590(17), c = 0.91360(6) nm,,beta = 106.1840(10)degrees, V= 2.5606(3) nm(3), Dc = 1.366 g/cm(3), Z = 8, F(000) = 1104, mu(MoK alpha) = 3.182 mm(-1), S = 0.837, the final R = 0.0460 and wR = 0.1033. Crystal X-ray diffraction analysis for 2c showed that its ring skeleton adopts [3333] conformation, in which the OH group presents at the side-exo position and the other one at the corner carbon. The H-1 NMR data of 2 showed that 1-corner-R-2-side-exo-OH [3333] and 1-corner-OH-2-side-exo-R [3333] conformations coexist in dynamic equilibrium in the solution, but only the former presents in the crystal.