36043-87-5Relevant academic research and scientific papers
Ion Pair-Directed Regiocontrol in Transition-Metal Catalysis: A Meta-Selective C-H Borylation of Aromatic Quaternary Ammonium Salts
Davis, Holly J.,Mihai, Madalina T.,Phipps, Robert J.
supporting information, p. 12759 - 12762 (2016/10/13)
The use of noncovalent interactions to direct transition-metal catalysis is a potentially powerful yet relatively underexplored strategy, with most investigations thus far focusing on using hydrogen bonds as the controlling element. We have developed an ion pair-directed approach to controlling regioselectivity in the iridium-catalyzed borylation of two classes of aromatic quaternary ammonium salts, leading to versatile meta-borylated products. By examining a range of substituted substrates, this provides complex, functionalized aromatic scaffolds amenable to rapid diversification and more broadly demonstrates the viability of ion-pairing for control of regiochemistry in transition-metal catalysis.
The effect of the nature of the amine leaving group on the nature of the E2 transition state for the reaction of 1-phenylethylammonium ions with sodium ethoxide in ethanol
Smith, Peter James,Amin, Md.
, p. 1457 - 1467 (2007/10/02)
To investigate the effect of the leaving group on the elimination reaction of 1-phenylethylammonium ions with sodium ethoxide in ethanol at 60 deg C, the reaction of seven different quaternary ammonium salts and their β-deuterated analogues with trimethylamine, N-methylpiperidine, N-methyldiethylamine, triethylamine, N,N-dimethylbenzylamine, tripropylamine, and N,N-diethylbenzylamine as leaving groups has been studied.In all cases the elimination, which was shown to proceed via the concerted E2 process, was accompained by competing substitution reactions.Although a significant depedence of the rate of the elimination process on the nature of the leaving group was noted, there was not any linear correlation with the basicity of the amine leaving group.The primary hydrogen-deuterium kinetic isotope effect for the elimination process, (kH/kD)E, was found to increase initially with an increase of reaction rate, kHE, for substrates containing the leaving groups trimethylamine, N-methylpiperidine, N-methyldiethylamine, triethylamine, and N,N-dimethylbenzylamine; i.e., (kH/kD)E=5.03, 5.26, 5.40, 5.83, and 5.85, respectively.A further increase in rate, using substrates with tripropylamine and N,N-diethylbenzylamine as leaving groups resulted in a decrease of the magnitude of the hydrogen-deuterium isotope effect; i.e., (kH/kD)E= 5.42 and 4.67, respectively.It is concluded that steric effects mainly determine leaving group ability.As well, it is concluded that the leaving group ability of the amine determines the structure of the E2 transition state.For the reaction of the poorer leaving groups, trimethylamine, N-methylpiperidine, and N-methyldiethylamine, the proton is more than one-half transferred at the transition state while for reaction involving the two best leaving groups, tripropylamine and N,N-diethylbenzylamine, the Cβ-H bond is less than one-half broken at the transition state.The conclusions are considered in the light of the More O'Ferrall-Jencks potential energy surface diagram.Key words: elimination mechanism, transition state, isotope effects, leaving group, quaternary salts.
Stereochemistry of Photosolvolysis of (-)-1-Phenylethyltrimethylammonium Iodide in Water and in Methanol, and Nucleophile Capture Ratios during Photosolvolysis of Some Benzylammonium Salts
Lillis, Veronica,Kenna, James Mc,Kenna, Jean Mc,Smith, Martin J.,Taylor, Paul S.,Williams, Ian H.
, p. 83 - 86 (2007/10/02)
The photosolvolysis of (-)-1-phenylethyltrimethylammonium iodide in water or methanol is characterised by extensive racemisation accompanied by some net configurational inversion, a result similar to that generally observed in thermal solvolysis via ion-pairs at chiral secondary centres.Recovered quaternary salt from the photolysis in water is only slightly if at all racemised, while likewise there is no observable epimerisation at nitrogen in recovered benzylammonium salts following photolysis in methanol of suitable derivatives of camphidine, trans-decahydroquinoline, and 4-phenylpiperidine.A strong preference for formation of the methyl ether rather than the alcohol is exhibited on either photochemical or thermal solvolysis of 1-p-methoxyphenylethyltrimethylammonium iodide in aqueous methanol, but nucleophile capture ratios during photosolvolysis of simple benzyltrimethylammonium salts in this mixed solvent system are much lower.
