Enhancing the Reactivity of an Electrophilic Barbiturate Dye by Cooperative Hydrogen Bonding

Abstract

The supramolecular complex formation by cooperativehydrogen bonding of a highly dipolar barbiturate dye and 2,6‐diacetamidopyridine is shown to have a marked effect on the reactivity of the barbiturate. The increase of both Lewis acidity and electrophilicity by hydrogen bonding is demonstrated by thermodynamic and kinetic studies using the electrophile–nucleophile recombination reaction with cyanide.

Solvent effects on the absorption spectra of potentially pharmacologically active 5-alkyl-5-arylhydantoins: A structure-property relationship study

“…18 Hereto, their absorption spectra _______________________________________________________________________________________________________________________ Copyright (C)2013 SCS Available online at www.shd.org.rs/JSCS/ STRUCTURE-PROPERTY RELATIONSHIP STUDY OF 5-ALKYL-5-ARYLHYDANTOINS 629 have been recorded in the region 200-400 nm in twelve solvents. 18 Hereto, their absorption spectra _______________________________________________________________________________________________________________________ Copyright (C)2013 SCS Available online at www.shd.org.rs/JSCS/ STRUCTURE-PROPERTY RELATIONSHIP STUDY OF 5-ALKYL-5-ARYLHYDANTOINS 629 have been recorded in the region 200-400 nm in twelve solvents.…”

Adjustable Electrophilicity by Cooperative Hydrogen Bonds

“…[4] The other two nucleophiles react quantitatively, so that solely the rate constant k 2,1 is accessible (see Table 2). The determined values for k 2,1 do not correlate with the nucleophilicity parameters N of Mayr et al…”

“…As model electrophiles we used the barbiturate merocyanines 1 a [4] and 1 b [5] shown in Scheme 1. These may also be described by zwitterionic resonance structures which explains the strong polarization of the central CÀC double bond.…”

Justierbare Elektrophilie durch kooperative Wasserstoffbrücken

“…Für die Untersuchungen nutzten wir die in Schema 1 gezeigten Barbiturat-Merocyanine 1 a [4] und 1 b [5] als Modellelektrophile. Diese kçnnen auch durch zwitterionische Resonanzstrukturen beschrieben werden, was die starke Polarisation der zentralen C-C-Doppelbindung erklärt.…”

“…[4] Die anderen beiden Nucleophile hingegen reagieren quantitativ, sodass in diesen Fällen nur die Geschwindigkeitskonstante k 2,1 zugänglich ist (Tabelle 2). Dass die ermittelten Werte für k 2,1 nicht mit den Nucleophilie-Parametern N nach Mayr [11] korrelieren, kann zum Teil auf die unterschiedlichen Referenzlçsungsmittel zurückgeführt werden.…”