52688-74-1Relevant academic research and scientific papers
Ga(OTf)3-mediated synthesis of substituted benzofurans
Wang, Heui-Sin,Chan, Chieh-Kai,Chang, Meng-Yang
, p. 5132 - 5141 (2016)
A synthetic procedure, for the synthesis of a series of functionalized benzofurans 3–5 and benzonaphthofurans 6, starting from intermolecular O-alkylation of α-bromoaryl ketones 2 with potassium oxygenated phenoxides 1 followed by Ga(OTf)3-catalyzed direct intramolecular cyclodehydration of the resulting α-aryloxyaryl ketones, has been developed. The use of various metal triflates was investigated for a facile approach and efficient transformation. Pentacyclic benzophenanthrofurans 7 were prepared via photolytic annulations of 5.
Ambident Reactivity of Phenolate Anions Revisited: A Quantitative Approach to Phenolate Reactivities
Mayer, Robert J.,Breugst, Martin,Hampel, Nathalie,Ofial, Armin R.,Mayr, Herbert
, p. 8837 - 8858 (2019/07/08)
Prompted by the observation that the regioselectivities of phenolate reactions (C versus O attack) are opposite to the predictions by the principle of hard and soft acids and bases, we performed a comprehensive experimental and computational investigation of phenolate reactivities. Rate and equilibrium constants for the reactions of various phenolate ions with benzhydrylium ions (Aryl2CH+) and structurally related quinone methides have been determined photometrically in polar aprotic solvents. Quantum chemical calculations at the SMD(MeCN)/M06-2X/6-31+G(d,p) level confirmed that O attack is generally favored under kinetically controlled conditions, whereas C attack is favored under thermodynamically controlled conditions. Exceptions are diffusion-limited reactions with strong electrophiles, which give mixtures of products arising from O and C attack, as well as reactions with metal alkoxides in nonpolar solvents, where oxygen attack is blocked by strong ion pairing. The Lewis basicity (LB) and nucleophilicity (N, sN) parameters of phenolates determined in this work can be used to predict whether their reactions with electrophiles are kinetically or thermodynamically controlled and whether the rates are activation- or diffusion-limited. Comparison of the measured rate constants for the reactions of phenolates with carbocations with the Gibbs energies for single-electron transfer manifests that these reactions proceed via polar mechanisms.
