A Surprising “Folded-In” Conformation of a Self-Assembled Arsenic-Thiolate Macrocycle
摘要:
The synthesis and crystal structures of two new macrocyclic compounds, As(2)(L(2,5))(2)Cl(2) and As(2)(L(2,3))(2)Cl(2), are described, where L(2,3) and L(2,5) are dithiolate ligands. For each compound, several diastereomeric isomers are possible (anti-"aligned", syn-"aligned", anti-"unaligned", syn-"unaligned"), as shown by density functional theory (DFT) calculations, but only one is crystallized out of solution. For As(2)(L(2,5))(2)Cl(2), only the anti-aligned isomer crystallizes, as expected based on steric arguments and backed up by DFT calculations. Surprisingly, for As(2)(L(2,3))(2)Cl(2), an anti isomer crystallizes in which one As-Cl unit has folded into the macrocyclic cavity. While this goes against steric arguments and DFT calculations, this conformation best fills the space within the cavity, avoiding the entropic cost of a large void.
Stereoretentive Ring-Opening Metathesis Polymerization to Access All-<i>cis</i> Poly(<i>p</i>-phenylenevinylene)s with Living Characteristics
作者:Ting-Wei Hsu、Cheoljae Kim、Quentin Michaudel
DOI:10.1021/jacs.0c04068
日期:2020.7.15
groups. While many synthetic methods afford PPVs with all-trans stereochemistry, very few deliver the all-cis congeners. We report herein a synthesis of all-cis PPVs with living characteristics via stereoretentive ring-openingmetathesis polymerization (ROMP). Exquisite catalyst control allows for the preparation of homopolymers or diblock copolymers with perfect stereoselectivity, narrow dispersities
5,8-Dimethyl-1,12-dimethylene-2,11-dithia[3.3]cyclophane 2,11-dioxides with planar and centralchirality were synthesized in high yields, starting from 2,5-dimethyl-1,4-benzenedimethanethiol, through the formation of suitable transient sulfenic functions that add to the triple bonds of disubstituted benzenes. Experimental observations allowed mechanistic and stereochemical insights into the key step
A New Method for the Synthesis of Imidazolidinone- and Benzimidazolone-Containing [2.2]Cyclophanes
作者:Keisha K. Ellis、Burkhardt Wilke、Yuegang Zhang、Steven T. Diver
DOI:10.1021/ol0064866
日期:2000.11.1
nucleophilic addition of bisthiols to heterocyclic bisacetals gives sulfur-containing macrocycles in good yield. Crossover experiments revealed that the acid-catalyzed N-acyl iminium cyclization for the imidazolidinones is reversible. The sulfur atom in the bridge was extruded photochemically, giving new [2.2]heterophanes containing the imidazolidinone and benzimidazolone ring systems. The determined crystal