[Pd(Cl)₂{P(NC₅H₁₀)(C₆H₁₁)₂}₂]—A Highly Effective and Extremely Versatile Palladium‐Based Negishi Catalyst that Efficiently and Reliably Operates at Low Catalyst Loadings

Abstract

[Pd(Cl)(2){P(NC(5)H(10))(C(6)H(11))(2)}(2)] (1) has been prepared in quantitative yield by reacting commercially available [Pd(cod)(Cl)(2)] (cod=cyclooctadiene) with readily prepared 1-(dicyclohexylphosphanyl)piperidine in toluene under N(2) within a few minutes at room temperature. Complex 1 has proved to be an excellent Negishi catalyst, capable of quantitatively coupling a wide variety of electronically activated, non-activated, deactivated, sterically hindered, heterocyclic, and functionalized aryl bromides with various (also heterocyclic) arylzinc reagents, typically within a few minutes at 100 °C in the presence of just 0.01 mol% of catalyst. Aryl bromides containing nitro, nitrile, ether, ester, hydroxy, carbonyl, and carboxyl groups, as well as acetals, lactones, amides, anilines, alkenes, carboxylic acids, acetic acids, and pyridines and pyrimidines, have been successfully used as coupling partners. Furthermore, electronic and steric variations are tolerated in both reaction partners. Experimental observations strongly indicate that a molecular mechanism is operative.

Probing the Origin of Magnetic Anisotropy in a Dinuclear {MnIIICuII} Single‐Molecule Magnet: The Role of Exchange Anisotropy

“…Alternative reactions of aryl organometallics with 2‐bromopyridine also give efficient couplings. For example, couplings of 2‐bromopyridine with arylboronic acids or7a,15 aryltrifluoroborates,8d or arylsilicon,7h,16 arylzinc,7f,17 aryltin,18 arylmagnesium,7l,19 arylmanganese,20 arylindium,9 or arylbismuth21 reagents have been reported under a variety of coupling conditions. The recently reported couplings of 2‐bromopyridine with triphenylbismuth14 needed overnight heating at 130 °C.…”

“…Arylation of 3‐bromopyridine has been achieved with ionic‐liquid‐supported aryltin reagents, in palladium‐catalysed Stille couplings 7e. Other couplings of 3‐bromopyridine with aryl organometallics such as arylboronic acids, [7b–7d,22] or arylsilicon,7h,23 aryltin,7e,24 arylaluminium,7i arylmagnesium,18,25 or arylzinc17 reagents are also known. It is important to note that BiAr 3 compounds are less toxic than ArSnR 3 compounds, and, unlike ArZnX or ArAlX 2 compounds, they are not air or moisture sensitive.…”

Carbon–Carbon Bond Forming Reactions Mediated by Organozinc Reagents

“…It is also worthy to note that in a related manner, the palladium complex derived from 1-(dicyclohexylphosphanyl)piperidine is also a highly efficient catalyst that operates in NMP at 100 • C at very low catalyst loadings. However, its applicability to aryl chlorides has not been disclosed [135]. Highly active palladium catalysts can also be obtained using bulky electrondonating N-heterocyclic carbene (NHC) ligands.…”

Evaluation of New Dihydrophthalazine-Appended 2,4-Diaminopyrimidines against Bacillus anthracis: Improved Syntheses Using a New Pincer Complex

“…The recent development of pincer complexes has permitted milder reaction conditions, better substrate scope, and lower catalyst loading to afford cleaner products in higher yields. Frech and coworkers have synthesized dichlorobis[1-(dicyclohexylphosphanyl)piperidine]palladium(II) (Pd pincer-II, see Figure 2 ), which performs arylations of olefins using a wide variety of substrates, including activated, unactivated and deactivated systems, as well as heterocyclic aryl bromides and various substituted olefins [ 21 , 22 ]. This aminophosphine palladium complex offers a superior conversion rate by forming palladium nanoparticles and functions as a homogeneous catalyst.…”