Direct observation of key intermediates by negative-ion electrospray ionisation mass spectrometry in palladium-catalysed cross-coupling

Abstract

Negative-ion electrospray ionisation mass spectrometry with an anionic phosphine ligand enables detection of key intermediates in the Sonogashira reaction. MS/MS techniques are used to generate a Hammett plot for the key reductive elimination step.

Gas-Phase Intramolecular Cyclization of Argentinated N-Allylbenzamides

“…Its first application in gas phase was conducted by McLafferty in 1959 [46], who found out that the logarithm of the ratio of the fragment ion to the precursor ion increases linearly with the increase in the substituent constants. From then on, Hammett plots have been extensively employed in the study of gas-phase chemistry [47][48][49][50] owing to its intuitive presentation of the substituent effect on the direct cleavage as well as on competitive fragmentation pathways. To get a more direct understanding on the relationship between substituents and competitive pathways, the logarithm of the intensity ratios of these two competitive product ions are usually utilized to plot with the substituent constants [31,37,50,51].…”

Alkylation of [Pt2(μ-S)2(PPh3)4] with boronic acid derivatives

“…An overpressure of 2 -4 psi is applied displacing the reacting solution into the MS. This allows for real-time observation of all charged species and how they behave over the course of the reaction, [31][32][33][34] and providing a better understanding of mechanism and optimization of synthetic protocols. For this report speciation and dynamic behavior in the reaction of 1 with 4-(bromomethyl)phenylboronic acid pinacol ester, BrCH2(C6H4)B{OC(CH3)2}2, 2 was monitored.…”

Cross‐Coupling Reactions to sp Carbon Atoms

“…The most widely used catalyst precursors for the reaction are [Pd(0)(PPh 3 ) 4 ] and [Pd(II)(PPh 3 ) 2 Cl 2 ]. In both cases, [Pd(0)(PPh 3 ) 2 ] is generally anticipated as the active catalyst that has recently been observed in the gas phase by negative-ion electrospray ionization mass spectrometry [18]. However, there is strong experimental evidence that halides from ArX in solution lead to an anionic [Pd(0)L 2 X] − , acting as the active catalytic species [19].…”