New sulfur derivatives of 2,3-dichloropyrrolo[1,2-a] benzimidazol-1-one. Demonstration of regioselective thiolate addition and X-ray diffraction structures of 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one
作者:William H. Watson、Guanmin Wu、Shih-Huang Huang、Michael G. Richmond
DOI:10.1007/s10870-004-7653-0
日期:2004.11
The reaction of thiols with the heterocyclic compound 2,3-dichloropyrrolo[1,2-a] benzimidazol-1-one (1) has been investigated as a route to new redox-active, bidentate sulfur ligands. Treatment of 1 with either methylthiol or benzylthiol in the presence of pyridine affords monosulfide compounds 2-chloro-3-methylthiopyrrolo[1,2-a] benzimidazol-1-one (2) and 2-chloro-3-benzylthiopyrrolo[1,2-a]benzimidazol-1-one (3) and the disulfide derivatives 2,3-di(methylthio)pyrrolo[1,2-a]benzimidazol-1-one (4) and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one (5). The substitution of the first chlorine group in 2,3-dichloropyrrolo[1,2-a]benzimidazol-1-one (1) occurs regioselectively at C-3 to produce 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one (2) and 2-chloro-3-benzylthiopyrrolo[1,2-a]benzimidazol-1-one (3), followed by replacement of the remaining chlorine group to furnish the disulfide compounds 4 and 5. The new thiols have been isolated by column chromatography and characterized in solution by spectroscopic methods. The molecular structures of 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one have been determined by X-ray crystallography. Compound 2 crystallizes as two independent molecules in the monoclinic space group P21/c, a = 13.221(2) Å, b = 18.478(2) Å, c = 8.948(1) Å, β = 100.088(3)°, V = 2152.3(5) Å3, Z = 8, and dcalc = 1.547 Mg/m3; R = 0.0354, Rw = 0.0739 for 2820 reflections with I > 2σ(I). Compound 5 crystallizes in the triclinic space group P-1, a = 5.180(1) Å, b = 11.494(2) Å, c = 17.243(3) Å, α = 86.024(3)°, β = 88.606(4)°, γ = 81.235(3)°, V = 1012.1(4) Å3, Z = 2, and dcalc = 1.360 Mg/m3; R = 0.0354, Rw = 0.0692 for 2655 reflections with I > 2σ(I). The redox properties of the disulfide compounds 4 and 5 have been explored by cyclic voltammetry, where a one-electron reduction at ca. −1.10 V has been observed for each compound. The site of electron accession in has been established by carrying out molecular orbital calculations at the extended Hüuckel level on the model compound 2,3-di(thio)pyrrolo[1,2-a]benzimidazol-1-one.
硫醇与杂环化合物 2,3-二氯吡咯并[1,2-a]苯并咪唑-1-酮 (1) 的反应已被研究作为获得新的氧化还原活性双齿硫配体的途径。在吡啶存在下用甲硫醇或苄硫醇处理 1 得到单硫化合物 2-氯-3-甲硫基吡咯并[1,2-a]苯并咪唑-1-酮 (2) 和 2-氯-3-苄硫基吡咯并[1,2] -a]苯并咪唑-1-酮 (3) 和二硫化物衍生物 2,3-二(甲硫基)吡咯并[1,2-a]苯并咪唑-1-酮 (4) 和 2,3-二(苄硫基)吡咯[ 1,2-a]苯并咪唑-1-酮(5)。 2,3-二氯吡咯并[1,2-a]苯并咪唑-1-酮 (1) 中第一个氯基团的取代在 C-3 处发生区域选择性,生成 2-氯-3-甲硫基吡咯并[1,2-a]苯并咪唑-1-酮(2)和2-氯-3-苄基硫代吡咯并[1,2-a]苯并咪唑-1-酮(3),然后取代剩余的氯基团以提供二硫化物化合物4和5。新的硫醇已通过柱色谱法分离出来,并通过光谱方法在溶液中进行表征。 2-氯-3-甲硫基吡咯并[1,2-a]苯并咪唑-1-酮和2,3-二(苄硫基)吡咯并[1,2-a]苯并咪唑-1-酮的分子结构已通过X确定射线晶体学。化合物 2 在单斜空间群 P21/c 中结晶为两个独立分子,a = 13.221(2) Å, b = 18.478(2) Å, c = 8.948(1) Å, β = 100.088(3)°, V = 2152.3(5) Å3,Z = 8,dcalc = 1.547 Mg/m3;对于 2820 次反射,I > 2σ(I),R = 0.0354,Rw = 0.0739。化合物 5 在三斜空间群 P-1 中结晶,a = 5.180(1) Å, b = 11.494(2) Å, c = 17.243(3) Å, α = 86.024(3)°, β = 88.606(4) °,γ = 81.235(3)°,V = 1012.1(4) Å3,Z = 2,dcalc = 1.360 Mg/m3;对于 2655 次反射,且 I > 2σ(I),R = 0.0354,Rw = 0.0692。二硫化物化合物 4 和 5 的氧化还原性质已通过循环伏安法进行了探索,其中单电子在约 1 处还原。每种化合物均观察到-1.10 V。通过对模型化合物 2,3-二(硫代)吡咯并[1,2-a]苯并咪唑-1-酮进行扩展 Hüuckel 能级的分子轨道计算,确定了电子加入位点。