Pyridine-Containing m-Phenylene Ethynylene Oligomers Having Tunable Basicities
摘要:
Incorporation of a pyridine monomer into the backbone of a m-phenylene ethynylene oligomer allows functionalization of the interior binding cavity of the folded oligomer. The basicity of the inwardly directed pyridine moiety was modulated by changing the substituents on the pyridine ring and through oligomer folding, granting access to a pK(a) range of 5-14 in acetonitrile.
Preparation of Shape-Persistent Macrocycles with a Single Pyridine Unit by Double Cross-Coupling Reactions of Aryl Bromides and Alkynes
作者:Ryu Yamasaki、Atsushi Shigeto、Shinichi Saito
DOI:10.1021/jo2018944
日期:2011.12.16
A double Sonogashira-type coupling reaction between arylbromides and alkynes using a catalytic Pd/XPhos (2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl) system was introduced as an efficient method for the synthesis of shape-persistent macrocycles (SPMs). This approach is advantageous in the synthesis of SPMs with a single pyridine unit.
Pyridine-Containing <i>m</i>-Phenylene Ethynylene Oligomers Having Tunable Basicities
作者:Jennifer M. Heemstra、Jeffrey S. Moore
DOI:10.1021/ol0363016
日期:2004.3.1
Incorporation of a pyridine monomer into the backbone of a m-phenylene ethynylene oligomer allows functionalization of the interior binding cavity of the folded oligomer. The basicity of the inwardly directed pyridine moiety was modulated by changing the substituents on the pyridine ring and through oligomer folding, granting access to a pK(a) range of 5-14 in acetonitrile.
Single-Site Modifications and Their Effect on the Folding Stability of <i>m</i>-Phenylene Ethynylene Oligomers
作者:Hirofumi Goto、Jennifer M. Heemstra、David J. Hill、Jeffrey S. Moore
DOI:10.1021/ol036376+
日期:2004.3.1
The folded structure of a m-phenylene ethynylene oligomer is tolerant to single-site modifications to both the backbone sequence and end groups. The helical structure is reinforced by multiple noncovalent interactions, allowing the oligomer sequence to be customized without a significant change in stability in most cases. The small changes that are observed are consistent with the expected behavior of pi-stacked systems and demonstrate subtle control over folding through single-site modifications.
Foldamers as Reactive Sieves: Reactivity as a Probe of Conformational Flexibility
作者:Ronald A. Smaldone、Jeffrey S. Moore
DOI:10.1021/ja067670a
日期:2007.5.1
A series of m-phenyleneethynylene (mPE) oligomers modified with a dimethylaminopyridine (DMAP) unit were treated with methyl sulfonates of varying sizes and shapes, and the relative reactivities were measured by UV spectrophotometry. Using a small-molecule DMAP analogue as a reference, each of the methyl sulfonates was shown to react at nearly identical rate. In great contrast, oligomers that are long enough to fold, and hence capable of binding the methyl sulfonate, experience rate enhancements of 18-1600-fold relative to that of the small-molecule analogue, depending on the type of alkyl chain attached to the guest. Three different oligomer lengths were studied, with the longest oligomers exhibiting the fastest rate and greatest substrate specificity. Even large, bulky guests show slightly enhanced methylation rates compared to that with the reference DMAP, which suggests a dynamic nature to the oligomer's binding cavity. Several mechanistic models to describe this behavior are discussed.
Folding-Promoted Methylation of a Helical DMAP Analogue
作者:Jennifer M. Heemstra、Jeffrey S. Moore
DOI:10.1021/ja031842b
日期:2004.2.1
The methylation rate for a series of pyridine-containing phenylene ethynylene oligomers shows a nonlinear dependence on chain length, with a significant rate enhancement observed for oligomers that adopt a folded, helical conformation. The folded structure provides a microenvironment that lowers the energy barrier for the methylationreaction. Of these noncovalent interactions, the largest stabilization