Trialkylammonium salt degradation: implications for methylation and cross-coupling

Abstract

Trialkylammonium (most notably N,N,N-trimethylanilinium) salts are known to display dual reactivity through both the aryl group and the N-methyl groups. These salts have thus been widely applied in cross-coupling, aryl...

Catalytic enantioselective synthesis of 1,4-dihydropyridines via the addition of C(1)-ammonium enolates to pyridinium salts

“…An N -benzyl derived substituent was essential for effective reactivity in this protocol; using N -methyl pyridinium salt 24 , no desired product was formed, with only starting materials returned. We speculate this could potentially be due to (i) alkylation of the isothiourea catalyst with 24 and inhibition of the catalytic reaction; 26 or (ii) stabilising π–cation or π–π interactions in the transition state involving the benzyl group; 27 however this was not investigated further.…”

Electrochemical Activation of Diverse Conventional Photoredox Catalysts Induces Potent Photoreductant Activity**

“…Theg eneration of aryl radical intermediates is aw ellestablished arena to benchmark new photoreductants.Benchstable [51][52][53][54] trialkylanilinium salts and activated phenols are readily accessible and can be reductively cleaved to aryl radical intermediates through deeply reducing direct electrolysis or alkali metal reductants,h owever,t hey remain difficult to activate under photocatalytic conditions. [55,56] Within the past year, Larionov and Kçnig illustrated that anilide and thiolate photocatalysts are capable of promoting the borylation of anilinium salts and activated phenols via photoreduction.…”

Ammonium Salts as Convenient Radical Precursors Using Iridium Photoredox Catalysis

“…As an alternative to diazonium 6 and Katritzky salts, 7 which are now common radical precursors suffering however from limitations in terms of safety and atom economy, ammonium salts constitute ideal candidates as they are stable, safe, and easily prepared on a multigram scale while only releasing a trialkyl amine as a side product upon activation. 8 While the activation of ammonium salts via oxidative addition of the C− N bond to a metal catalyst is already established, 9 their reductive activation via SET has remained understudied until recently, as ammonium salts are highly challenging to reduce (E 1/2 < −2 V vs SCE). In recent years, an increased interest for such activation of ammonium salts led to the development of some radical processes for their reduction and/or functionalization.…”