نتایج جستجو برای: chemoselectivity
تعداد نتایج: 401 فیلتر نتایج به سال:
Allylic alcohols are valuable precursors in the synthesis of pharmaceutical intermediates, agrochemicals and natural products. Regioselective oxidation of parental alkenes is a challenging task for chemical catalysts and requires several steps including protection and deprotection. Many cytochrome P450 enzymes are known to catalyse selective allylic hydroxylation under mild conditions. Here, we...
The enantioselective photoenzymatic reduction of a wide variety ketones to the corresponding alcohols using promiscuous nitroreductase BaNTR1 is reported. This flavoenzyme not only shows outstanding enantioselectivity but also remarkably high chemoselectivity, promoting various α,ß-unsaturated give desired enantioenriched without reducing C=C or C≡C bond.
The intramolecular carbothiolation of unsaturated hydrocarbons using a palladium–NHC catalyst (NHC = N-heterocyclic carbene) is described. Herein, single system enables both initial activation C(sp2)–S bond through oxidative addition and formation C(sp3)–S terminal reductive elimination, unlocking completely atom-economical transfer across alkenes. reaction tolerates variety different functiona...
A model halogenated aryl ketone (4-chloropropiophenone 1) was subjected to mild catalytic hydrodehalogenation (p[H2] ) 1 atm, T ) 50 °C) in a multiphase system consisting of isooctane and an alkaline aqueous phase, in the presence of onium salts as phase-transfer agents. The chemoselectivity of the reaction was sharply influenced by the KOH concentration of the aqueous phase: thus, the formatio...
The adsorption and hydrogenation of acrolein on the Ag(111) surface has been investigated by high resolution synchrotron XPS, NEXAFS, and temperature programmed reaction. The molecule adsorbs intact at all coverages and its adsorption geometry is critically important in determining chemoselectivity toward the formation of allyl alcohol, the desired but thermodynamically disfavored product. In t...
[reaction: see text] In the presence of NaY faujasite as the catalyst, the reaction of bifunctional anilines (1-4: XC6H4NH2; X = OH, CO2H, CH2OH, and CONH2) with methyl alkyl carbonates [MeOCO2R': R' = Me or MeO(CH2)2O(CH2)2] proceeds with a very high mono-N-methyl selectivity (XC6H4NHMe up to 99%), and chemoselectivity as well, with other nucleophilic functions (OH, CO2H, CH2OH, CONH2) fully p...
We report a photochemical method for the chemoselective radical functionalization of tryptophan (Trp)-containing peptides. The exploits photoactivity an electron donor-acceptor complex generated between unit and pyridinium salts. Irradiation with weak light (390 nm) generates intermediates right next to targeted Trp amino acid, facilitating proximity-driven functionalization. This protocol exhi...
We introduce a stabilized diazo group as a reporter for chemical biology. ManDiaz, which is a diazo derivative of N-acetylmannosamine, is found to endure cellular metabolism and label the surface of a mammalian cell. There its diazo group can undergo a 1,3-dipolar cycloaddition with a strained alkyne, providing a signal comparable to that from the azido congener, ManNAz. The chemoselectivity of...
A novel method for the mono-N-alkylation of primary amines, diamines, and polyamines was developed using cesium bases in order to prepare secondary amines efficiently. A cesium base not only promoted alkylation of primary amines but also suppressed overalkylations of the produced secondary amines. Various amines, alkyl bromides, and alkyl sulfonates were examined, and the results demonstrated t...
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