Tailoring Buchwald-Type Phosphines with Pyrimidinium Betaines as Versatile Aryl Group Surrogates

Abstract

A derivatization of dialkylbiarylphosphines consisting in the formal replacement of their distal aryl group by a pyrimidinium betaine is reported. Two achiral representatives of this new class of Buchwald-type phosphines have been successfully synthesized through two strategies. The first one is based on a last stage introduction of the phosphino moiety, and the second one consists in a modular, one-pot, three-step procedure starting from an o-bromoaryl phosphine. The resulting phosphines have been coordinated onto gold(I) and palladium(II) centers and have been employed as supporting ligands in Pd-catalyzed Suzuki−Miyaura cross-coupling of aryl halide substrates.

Towards the rational design of ylide-substituted phosphines for gold(i)-catalysis: from inactive to ppm-level catalysis

“…6 , right). 8,25 All ligands were tested under the same reaction conditions, i.e. at 50 °C with 0.05 and 0.01 mol% catalyst loading.…”

“… 5,6 A similar strategy of improving the catalyst activity by modification of the catalytic pocket was recently applied to N-heterocyclic carbenes (NHCs) 7 as well as further dialkylbiaryl phosphines. 8 In case of hydroamination reactions, the best results however, were – to the best of our knowledge – reported by Lavallo and coworkers using an anionic phosphine and NHC with carborate substituents, giving rise to TONs close to 100 000. 9 Drawback of these highly sophisticated ligands however, is that they are often rather complicated to synthesize thus considerably contributing to the total costs of the catalyst.…”

Redox-responsive phosphonite gold complexes in hydroamination catalysis

“…In recent years, elegant variations of Buchwald-type biaryl phosphines have been reported by various groups. [7][8][9][10] Our group could recently show that the biaryl structural motif can also be included in redox-active phosphine ligands, in our case [1]phosphaferrocenophanes (II, Chart 1). 11 Palladium complexes thereof have been successfully applied in redox-induced 12 Buchwald-Hartwig amination reactions.…”

Attempted synthesis of ortho -phenylene phosphino-tritylium cations

“…(2-Bromophenyl)diphenylphosphine [45] and (2-bromophenyl)di-isopropyl phosphine [45] were synthesized according to the published procedure. Fluoroboric acid (HBF 4 ) and n-BuLi were purchased from Alfar Aesar; TFAA was purchased from Oakwood Products Inc.; benzophenone was purchased from J. T. Baker (Baker Analyzed).…”

“…(2-Bromophenyl)diphenylphosphine [45] and (2-bromophenyl)di-isopropyl phosphine [45] were synthesized according to the published procedure. Fluoroboric acid (HBF 4 ) and n-BuLi were purchased from Alfar Aesar; TFAA was purchased from Oakwood Products Inc.; benzophenone was purchased from J. T. Baker (Baker Analyzed After stirring at −78°C for 1 h, which resulted in the formation of the lithium salt as a colourless powder, benzophenone (0.730 g, 4.01 mmol) was added to the suspension.…”