Methoxycarbonylation of olefins catalyzed by palladium complexes bearing P,N-donor ligands

Abstract

The methoxycarbonylation of alkenes catalyzed by palladium(II) complexes with P,N-donor ligands, 2-(diphenylphosphinoamino)pyridine (Ph2PNHpy), 2-[(diphenylphosphino)methyl]pyridine (Ph2PCH2py), and 2-(diphenylphosphino)quinoline (Ph2Pqn) has been investigated. The results show that the complex [PdCl(PPh3)(Ph2PNHpy)]Cl or an equimolar mixture of [PdCl2(Ph2PNHpy)] and PPh3, in the presence of p-toluensulfonic acid (TsOH), is an efficient catalyst for this reaction. This catalytic system promotes the conversion of styrene into methyl 2-phenylpropanoate and methyl 3-phenylpropanoate with nearly complete chemoselectivity, 98% regioselectivity in the branched isomer, and high turnover frequency, even at alkene/Pd molar ratios of 1000. Best results were obtained in toluene-MeOH (3 : 1) solvent. The Pd/Ph2PNHpy catalyst is also efficient in the methoxycarbonylation of cyclohexene and 1-hexene, although with lower rates than with styrene. Related palladium complexes [PdCl(PPh3)L]Cl (L = Ph2PCH2py and Ph2Pqn) show lower activity in the methoxycarbonylation of styrene than that of the 2-(diphenylphosphinoamino)pyridine ligand. Replacement of the last ligand by (diphenylphosphino)phenylamine (Ph2PNHPh) or 2-(diphenylphosphinoaminomethyl)pyridine (Ph2PNMepy) also reduces significantly the activity of the catalyst, indicating that both the presence of the pyridine fragment as well as the NH group, are required to achieve a high performing catalyst. Isotopic labeling experiments using MeOD are consistent with a hydride mechanism for the [PdCl(PPh3)(Ph2PNHpy)]Cl catalyst.

The Variable Binding Modes of Phenylbis(pyrid‐2‐ylmethyl)phosphane and Bis(pyrid‐2‐ylmethyl) Phenylphosphonite with AgI and CuI

“…A wide variety of ligands containing a pyridyl functionality in conjuction with phosphorus in the form of phosphanes, phosphinites, phosphonites, phosphates and phosphazoles have been synthesized and studied. [1][2][3][4] Complexes synthesized with these ligands have exhibited catalytic [1,[5][6][7] and luminescence properties, as well as being useful in the construction of extended structures. [8][9][10][11] We have mainly been interested in synthesizing pyridylcontaining phosphinites and phosphonites where the pyridyl is attached at either the 3-or 4-position which precludes the formation of discrete chelating structures.…”

A survey of pendant donor-functionalised (N,O) phosphine ligands for Cr-catalysed ethylene tri- and tetramerisation

“…Ph 2 PN(i-Pr)P(Ph)N(i-Pr)H (1), 21 Ph 2 PN(2-pyridinel)H (2), 48 (Ph 2 P) 2 N-N(Ph)H (8) (ref. 46) and (2-hydroxyethyl)diphenylphosphine (14) (ref.…”

Methoxycarbonylation of Styrene Catalyzed by Palladium Complexes with Ferrocene Derivatives Containing Nitrogen and Phosphine Ligands

“…We have recently investigated the methoxycarbonylation of alkenes catalyzed by palladium(II) complexes with P,N-donor ligands. The results show that the [PdCl (PPh 3 )(Ph 2 PNHpy)]Cl complex or an equimolar mixture of [PdCl 2 (Ph 2 PNHpy)] and PPh 3 , in the presence of p-toluensulfonic acid (TsOH), are efficient catalysts for this reaction [20]. Palladium systems bearing chiral phosphetane ligands in the asymmetric methoxycarbonylation of styrene and vinyl arenes have been reported recently.…”