58765-11-0Relevant academic research and scientific papers
Isoflavone biosynthesis in Onobrychis viciifolia: Formononetin and texasin as precursors of afrormosin
Al-Ani, Hakim A.M.,Dewick, Paul M.
, p. 2337 - 2339 (1980)
4,2′,4′-Trihydroxychalcone- [carbonyl-14C], formononetin- [Me-14C] and texasin- [Me-14C] were all good precursors of afrormosin (7-hydroxy-6,4′-dimethoxyisoflavone) in Onobrychis viciifolia seedlings, and a biosynthetic pathway involving these intermediates is proposed. 2′,4′-Dihydroxy-4-methoxychalcone- [carbonyl-14C] and daidzein-[carbonyl-14C] were poor precursors. Incorporations into formononetin were also recorded.
3,4-Dimethyl-2,5-functionalized thieno[2,3-b[thiophenes: Versatile precursors for novel bis-thiazoles
Sayed, Osama M.,Mekky, Ahmed E.M.,Farag, Ahmad M.,Elwahy, Ahmad H.M.
, p. 124 - 134 (2015/10/20)
Synthesis of novel bis(thiazoles) 19-22, 24, 25, 30 and 31 is reported. Thus, reaction of the bis(α-bromoketones) 14 and 15 with the corresponding thioamide derivatives 16-18 in refluxing EtOH in the presence of triethylamine afforded 19-22 in good yields
A kinetic study on nucleophilic displacement reactions of aryl benzenesulfonates with potassium ethoxide: Role of K+ ion and reaction mechanism deduced from analyses of LFERs and activation parameters
Um, Ik-Hwan,Kang, Ji-Sun,Shin, Young-Hee,Buncel, Erwin
supporting information, p. 490 - 497 (2013/03/13)
Pseudofirst-order rate constants (kobsd) have been measured spectrophotometrically for the nucleophilic substitution reactions of 2,4-dinitrophenyl X-substituted benzenesulfonates 4a-f and Y-substituted phenyl benzenesulfonates 5a-k with EtOK in anhydrous ethanol. Dissection of k obsd into kEtO- and kEtOK (i.e., the second-order rate constants for the reactions with the dissociated EtO - and ion-paired EtOK, respectively) shows that the ion-paired EtOK is more reactive than the dissociated EtO-, indicating that K + ion catalyzes the reaction. The catalytic effect exerted by K + ion (e.g., the kEtOK/kEtO- ratio) decreases linearly as the substituent X in the benzenesulfonyl moiety changes from an electron-donating group (EDG) to an electron-withdrawing group (EWG), but it is independent of the electronic nature of the substituent Y in the leaving group. The reactions have been concluded to proceed through a concerted mechanism from analyses of the kinetic data through linear free energy relationships (e.g., the Bronsted-type, Hammett, and Yukawa-Tsuno plots). K+ ion catalyzes the reactions by increasing the electrophilicity of the reaction center through a cyclic transition state (TS) rather than by increasing the nucleofugality of the leaving group. Activation parameters (e.g., ΔH? and ΔS?) determined from the reactions performed at five different temperatures further support the proposed mechanism and TS structures.
A kinetic study on nucleophilic displacement reactions of phenyl Y-substituted-phenyl carbonates with alkali metal ethoxides: Metal ion effect and reaction mechanism
Um, Ik-Hwan,Seo, Ji-Yoon,Kang, Ji-Sun,An, Jun-Sung
, p. 1007 - 1013,7 (2020/08/24)
Pseudo-first-order rate constants (kobsd) have been measured for reactions of phenyl Y-substituted-phenyl carbonates with alkali metal ethoxides (EtOM, M = Li, Na, and K). The plot of kobsd vs. [EtOM] curves upward for the reaction of diphenyl carbonate with EtOM but is linear for that with EtOK in the presence of 18-crown-6-ether (18C6), indicating that the reaction is catalyzed by M+ ions and the catalytic effect disappears in the presence of 18C6. The kobsd values for the reactions with EtOK have been dissected into fEtO- and kEtOK, i.e., the second-order rate constants for the reactions with dissociated EtO- and ion-paired EtOK, respectively. The Hammett plots correlated with σ- and σ-0 constants exhibit highly scattered points, while the Yukawa-Tsuno plots result in an excellent linear correlation with p = 2.11 and r = 0.21 for kEtO-, and P = 1.62 and r = 0.26 for kEtOK, implying that the reaction proceeds through a concerted mechanism. The catalytic effect (i.e., the kEtOK/kEtOr ratio) is independent of the electronic nature of the substituent Y. Thus, it has been concluded that K+ ion catalyzes the reaction by increasing the electrophilicity of the reaction center.
Combined dual substituent constant and activation parameter analysis assigns a concerted mechanism to alkaline ethanolysis at phosphorus of Y-substituted phenyl diphenylphosphinates
Um, Ik-Hwan,Park, Jee Eun,Shin, Young-Hee
, p. 3539 - 3543 (2008/09/20)
Second-order rate constants have been measured for reactions of Y-substituted phenyl diphenylphosphinates (1a-h) with EtO-K + in anhydrous ethanol. A linear Bronsted-type plot is obtained with βLg = -0.54, a typical βLg value for reactions which proceed through a concerted mechanism. The Hammett plots correlated with σo and σ- constants are linear but exhibit many scattered points, while the corresponding Yukawa-Tsuno plot results in excellent linear correlation with r = 0.41. The r value of 0.41 indicates that the leaving group departs at the rate-determining step (RDS) whether the reactions proceed through either a concerted or a stepwise mechanism. However, a stepwise mechanism in which departure of the leaving group occurs at the RDS is excluded since the incoming EtO- ion is much more basic and a poorer leaving group than the leaving aryloxide. The ΔH? values determined in the current reactions are strongly dependent on the nature of the substituent Y, while the ΔS ? values remain constant on changing the substituent Y in the leaving group, i.e., from Y = H to Y = 4-NO2 and Y = 3,4-(NO 2)2. These ΔH? and ΔS ? trends also support a concerted mechanism. The Royal Society of Chemistry.
Surfactant-mediated solvent-free dealkylative cleavage of ethers and esters and trans-alkylation under neutral conditions
Bhattacharya, Apurba,Patel, Nitin C.,Vasques, Tomas,Tichkule, Ritesh,Parmar, Gaurang,Wu, Jiejun
, p. 565 - 567 (2007/10/03)
A simple, surfactant-mediated, one-pot, solvent-free dealkylative cleavage of aryl ethers and esters followed by subsequent optional trans-alkylation under essentially neutral conditions has been developed.
