Planar Chiral Dianthranilide and Dithiodianthranilide Molecules: Optical Resolution, Chiroptical Spectra, and Molecular Self-Assembly

Planar chiral dianthranilide (1) was resolved to enantiomers with use of (−)-(1S,4R)-camphanoyl
chloride as a chiral derivatizing agent. The (+)-1 enantiomer was assigned the S absolute
configuration from the X-ray crystal structure of its N,N‘-dicamphanoyl derivative. Optical resolution
of dithionodianthranilide (2) was accomplished by inclusion crystallization with (R,R)-1,2-diaminocyclohexane, and the X-ray structure of the corresponding adduct revealed the (−)-2
stereoisomer has the R configuration. A slow boat-to-boat ring inversion (ΔG⧧ = 24.1 ± 0.1 kcal
mol-1) causes racemization of (+)-1 in solution as manifested by a gradual decrease of the CD
spectrum whereas, (−)-2 is configurationally stable at these conditions. The analysis of the CD
spectra of the title compounds showed that the n−π* Cotton effect signs are determined by the
helicity of the skewed benzamide and thiobenzamide chromophores. The solid-state structures of
the racemic and homochiral forms of 1 and 2 show different self-assembly patterns:  the racemate
(±)-1 prefers the cyclic R22(8) hydrogen bond motif, whereas the crystalline DMSO solvates of (±)-1
and (+)-1 consist of 1D homochiral hydrogen-bonded assemblies generated by the C(6) motif. In
the case of dithionolactams (±)-2 and (−)-2 two types of 1D networks were observed:  in the racemate
they are generated by the centrosymmetric R22(8) and R22(12) hydrogen bond motifs, whereas the
molecules in the homochiral crystals are connected solely with use of the strongly nonplanar R22(8)
motif.

平面手性二邻氨基苯甲酰胺（1）以(−)-(1S,4R)-樟脑酰氯（camphanoyl chloride）作为手性衍生化试剂，被拆分为一对对映体。通过其N,N'-二樟脑酰衍生物的X射线晶体结构，将(+)-1对映体的绝对构型指定为S型。二硫代二邻氨基苯甲酰胺（2）的光学拆分通过与(R,R)-1,2-环己二胺的包结结晶（inclusion crystallization）法得以实现，对应加合物的X射线结构显示，(−)-2立体异构体的构型为R型。缓慢的船式-船式环翻转（ΔG⧧=24.1±0.1 kcal·mol⁻¹）会导致溶液中(+)-1发生外消旋化（racemization），具体表现为圆二色谱（Circular Dichroism，CD）光谱逐渐减弱；而(−)-2在该条件下构型保持稳定。对标题化合物的CD光谱分析表明，n-π*科顿效应（Cotton effect）的符号由扭曲的苯甲酰胺和硫代苯甲酰胺生色团（chromophore）的螺旋性决定。1和2的外消旋及同手性（homochiral）晶型的固态结构展现出不同的自组装模式：外消旋体(±)-1更倾向于形成环状R₂²(8)氢键基元（hydrogen bond motif），而(±)-1和(+)-1的结晶二甲基亚砜（Dimethyl Sulfoxide，DMSO）溶剂化物则由C(6)基元生成的一维同手性氢键组装体构成。对于二硫代内酰胺(±)-2和(−)-2，可观察到两种类型的一维网络：在外消旋体中，网络由中心对称的R₂²(8)和R₂²(12)氢键基元生成；而同手性晶体中的分子仅通过高度非平面的R₂²(8)基元相连。