Kinetics of the Reactions of Flavylium Ions with π-Nucleophiles

Abstract

Keywords: Kinetics / Linear free-energy relationships / Carbocations / Electrophilic additions / Nucleophilic additionsThe kinetics of the reactions of the flavylium ion 1a and the 4Ј-methoxyflavylium ion 1b with various π-nucleophiles and tributylstannane were investigated photometrically in dichloromethane. Electrophilicity parameters E(1a) = −3.46 and [a]

Organocatalytic Stereoselective α‐Alkylation of Aldehydes with Stable Carbocations

“…To examine the behavior of the stereogenic carbocation, flavylium triflate (4) was readily synthesized by the described procedure. [19] In general, flavylium ions are basic constituents of the anthocyanin pigment in plants. Besides their use as food colorants and dyes, an increased attention over their synthesis was also determined by their biological properties.…”

“…[20] Electrophilicity properties of the flavylium cation were described by Mayr. [19] The flavylium ion considered in our study is positioned at À3.45 of the Mayr scale. From the application of Equation (2), it is possible to conclude that flavylium will react with nucleophiles of N > À1.5.…”

Direct access to functionalized 4-nitromethyl-chromenes via a domino reaction under catalyst-free conditions

“…Based on previous work, trans-2-hydroxychalcone can be transformed into flavylium ion by acids. 12 Due to high temperature and protonic EtOH, there may be a similar process in this reaction. Moreover, during exploring the substrate scope, 1-(6-chloro-2-ethoxy-2methyl-2H-chromen-3-yl)ethanone (Scheme 2, e) was obtained through intramolecular cyclization under standard conditions and it didn't further react with CH 3 NO 2 .…”

Determination of Nitrites in Commercial Sausages by Anthocyanins Degradation. Experimental Design and Optimization

“…Fichtner and co-workers [8] have studied the kinetics of the reactions of the flavylium ion with π-nucleophiles (different from nitrite ion) and have described that the nucleophilic reactions happen more quickly in the C-4 position than in the C-2 position. Due to these results, the authors have concluded that the substitution happens mainly in the C-4 position.…”