We report convenient and high-yielding syntheses of new phosphine-functionalized dihydroimidazolium salts and demonstrate their utility as ligand precursors for Buchwald−Hartwig amination. Several examples of the general formula [1-Mes-3-{2-(PR 2 )phenyl}imidazolidin-2-ylium][BF 4 ] have been prepared, where phosphines of varying steric and electronic properties (R = Ph (9), Cy (10), 1-Ad (11)) are tethered by an o-phenylene group. The synthesis was not adaptable to N-aryl groups other than mesityl, giving unexpected phosphonium salt species instead. The synthesis was adapted to flexible benzyl-linked variants of the formula [1-Ar-3-{2-(PCy 2 )benzyl}imidazolidin-2-ylium][BF 4 ], which allowed more steric variation of the dihydroimidazolium Naryl group (Ar = Mes (21), Dipp ( 22)). A preliminary study of these hybrid NHC/P ligands in Buchwald−Hartwig amination catalysis (in situ precatalyst formation) revealed 11 to be the most active of the series. Premixing the isolated free NHC ligand 1-Mes-3-{2-(PAd 2 )phenyl}imidazolidin-2-ylidene ( 23) with [Pd(cinnamyl)Cl] 2 provided a highly active precatalyst that performed well at room temperature and 1 mol % catalyst loading. The system was shown to have an unprecedented ability to arylate both primary alkylamines (monoarylation) and secondary dialkylamines with aryl chlorides at room temperature. Electron-rich and -poor aryl and heteroaryl halides, as well as those featuring ortho substitution, were well tolerated, while substrates featuring both primary and secondary amine groups were selectively arylated at the NH 2 position. Furthermore, a preliminary examination of performance in ammonia arylation and acetone α-arylation showed promising results, giving good conversion and high selectivity for monoarylation in both cases.

Ligand design for metal–ligand cooperative (MLC) catalysis is inherently more complex than that for traditional non‐cooperative ligands. The basicity, sterics and structure of the acid/base group in MLC proton‐transfer (PT) complexes, for instance, undoubtedly influence catalyst performance. Herein, we evaluate the highly tunable PR2NR′2 (1,5‐R′‐3,7‐R‐1,5‐diaza‐3,7‐diphosphacyclooctane) ligand family for the first time in an organic transformation. With [Ru(Cp)(PtBu2NBn2)(MeCN)][PF6] as the catalyst, no turnover was observed in the anti‐Markovnikov hydration of alkynes, a known PT MLC reaction. Treatment of the cooperative complex with phenylacetylene affords a vinylammonium product in which the pendant nitrogen atom of the PtBu2NBn2 ligand forms a Lewis acid–base adduct with the alpha‐carbon atom of the vinylidene intermediate. Characterization by X‐ray crystallography and NMR spectroscopy conclusively assign this structure in both the solid and the solution state. The adduct formation is irreversible, and the adduct is characterized as a catalyst deactivation product.

Synthetic methods for carbon-11 chemistry are highlighted with particular importance put on the activation of [ 11 C]CO 2. Methods focus on practical, alternative routes to key intermediates for synthesis of radiotracers without the reliance on [ 11 C] phosgene. Recent advances display practical syntheses with [a] J.

Herein, we report a method for the isotopic labelling of hydantoins directly from CO2 by means of trimethyl-λ5-phosphine diiodide mediated carbonyl insertion. The method is suitable for 13C-labelling of diverse...