Hydrovinylation Reaction Research Articles

Three-Component Coupling of Acyl Fluorides, Silyl Enol Ethers, and Alkynes by P(III)/P(V) Catalysis.

We report herein on the phosphine-catalyzed hydrovinylation reaction by three-component coupling of acyl fluorides, silyl enol ethers, and alkynoates. The key to the success of the reaction is the formal transmetalation between pentacoordinate P(V) species (i.e., fluorophosphorane) and a silyl enol ether, which allows for C-C bond formation between the polarity-mismatched sites. The bond formation that cannot be attained even by transition metal catalysis is accomplished by a P(III)/P(V) manifold.

Allylic Oxidation of Ester-Substituted 1,4-Dienes.

The cobalt-catalyzed hydrovinylation reaction and the Alder-ene reaction generate acyclic 1,4-dienes, which were investigated in the selenium dioxide oxidation to afford further functionalized dienes prone for follow-up reactions. The chemoselective allylic oxidation of ester-functionalized 1,4-dienes occurs at the most electron-rich double bond. The steric demand of the electron-rich, alkyl-substituted double bond determines the reaction pathway, whether the double bond transposition toward the conjugated 1,3-diene or the allylic oxidation is faster. As reaction products, 2,4-diene-6-ols or divinyl ketones were obtained.

Metal catalysed hydrovinylation

An overview of the hydrovinylation reaction catalysed by transition metal organometallic complexes is given. The addition of ethylene to another CC double bond of vinylarenes, dienes or strained olefins is highlighted as an elegant methodology to generate a new stereogenic centre. In addition, the introduction of a new vinyl group allows further functionalisation. The parameters that control the selectivity of the formal codimerisation reaction and some selected applications are discussed.

ChemInform Abstract: Enantioselective Hydrovinylation via Asymmetric Counteranion‐Directed Ruthenium Catalysis.

AbstractThe first examples on the use of a ruthenium complex and a chiral silver salt as a catalytic system for an asymmetric hydrovinylation reaction are given.

Ruthenium-Catalyzed Hydrovinylation of N-Acetylenamines Leading to Amines with a Quaternary Carbon Center

A catalytic hydrovinylation of N-acetylenamines with ethylene is reported. This new hydrovinylation reaction is catalyzed by a ruthenium hydride complex, RuHCl(CO)(PCy(3))(2), providing a series of N-acetylamines with a quaternary carbon center with up to 99% yield.

Ethylene in organic synthesis. Repetitive hydrovinylation of alkenes for highly enantioselective syntheses of pseudopterosins.

In this report we highlight the significant potential of ethylene as a reagent for the introduction of a vinyl group with excellent stereoselectivity at three different stages in the synthesis of a broad class of natural products, best exemplified by syntheses of pseudopterosins. The late-stage applications of the asymmetric hydrovinylation reaction further illustrate the compatibility of the catalyst with complex functional groups. We also show that, depending on the choice of the catalyst, it is possible to either enhance or even completely reverse the inherent diastereoselectivity in the reactions of advanced chiral intermediates. This should enable the synthesis of diastereomeric analogs of several classes of medicinally relevant compounds that are not readily accessible by the existing methods, which depend on 'substrate control' for the installation of many of the chiral centers, especially in molecules of this class.

Development of Platinum(II) and -(IV) CNC Pincer Complexes and Their Application in a Hydrovinylation Reaction

A series of new, dicationic platinum(II) CNC pincer complexes were prepared and characterized by NMR and X-ray diffraction analysis. Oxidative addition of methyl iodide and iodine yielded the mostly unstable platinum(IV) complexes, which readily underwent reductive elimination to yield the platinum(II) precursors. Nonetheless, a platinum(IV) iodide adduct was isolated and was characterized by X-ray diffraction analysis. Additionally, a platinum(II) ethylene complex was isolated and found to be a moderately active yet highly selective catalyst in the co-dimerization of 2-methyl-2-butene with ethylene.

Modular Approach to New Chiral Monodentate Diamidophosphite Ligands. Application in Palladium-Catalyzed Asymmetric Hydrovinylation of Styrene

A new group of chiral monodentate diamidophosphite ligands (2 P−N/1 P−O bond) based on diazaphospholidine backbones derived from N,N′-dibenzylcyclohexane-1,2-diamine (7) and N,N′-dimethylcyclohexane-1,2-diamine (8), and diazaphosphepine backbones derived from N,N′-dimethyl-[1,1′-binaphthyl]-2,2′-diamine (9) and various chiral alkoxy groups (coming from phenylethanol a, borneol b, methyllactate c, allylic alcohol d, and methanol e) were prepared. The ligands have a highly modular structure, which is well suited to the synthesis of a small library. Preparation was readily accomplished by the successive addition of pure enantiomeric substituted diamine and pure enantiomeric alcohol to phosphorus trichloride. The corresponding diamidophosphite selenides Se(7−9) were prepared and the JPSe was calculated in order to evaluate the σ-donor ability of the new ligands. The reaction of [Pd(μ-Cl)(η3-2-CH3C3H4)]2 with the new diamidophosphite ligands (7−9) led to the monomeric allylic neutral complexes 11−13. Two isomers appeared in solution due to the R- or S-geometry around the palladium atom. The molecular structure determined by X-ray diffraction of the neutral complex [PdCl(η3-2-CH3C3H4)(7a)] (11a-(S,S,Sal)) showed a nonsymmetric coordination of the allyl moiety due to the greater trans influence of the phosphorus atom. The asymmetric hydrovinylation reaction between styrene and ethylene was tested using filtered CH2Cl2 solutions of [PdCl(η3-2-CH3C3H4)L] complexes and AgBF4 as catalytic precursors. The reaction performed at 15 °C and 15 bar of ethylene starting pressure led to good selectivities and moderate to good activities of 3-phenyl-1-butene. The best results were obtained when the cationic catalytic precursor contained the 9b-(R,Sal) diamidophosphite with a binaphthyl backbone and bornyloxy as the third substituent. With this system the TOF reached 595 h−1 of 3-phenyl-1-butene, whereas the ee was 90% toward the R-isomer.

Lewis Acid Activated Ni-Catalyzed Asymmetric Hydrovinylation

Lewis acids are able to activate a nickel catalyst for olefin hydrovinylation reaction by abstraction of the halide anion of the neutral nickel complex. The authors screened a series of Lewis acids and found InI3 to be the most effective activator for this reaction.

Nickel‐Catalyzed Asymmetric Hydrovinylation Using Lewis Acid Activation

AbstractA broad range of commercially available Lewis acids were investigated for their ability to activate and regulate nickel catalysts for asymmetric hydrovinylation processes using styrene as model substrate and ligand (Ra,SC,SC)‐5 as benchmark system. The colour change during the activation step associated with the halide abstraction furnishes helpful indications to adapt the activation conditions to the pre‐catalyst/Lewis acid system. In general, metal halide Lewis acids led to higher activities and enantioselectivities than the corresponding triflates. In particular, the use of InI3 as co‐catalyst resulted in the same chemo‐ and enantioselectivity and even higher activity than the benchmark system based onNaBArF. Moreover, InI3 is safe to handle and cheap, thus providing a simple and practical protocol for an efficient hydrovinylation reaction.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A Theoretical Investigation of the Ni(II)-Catalyzed Hydrovinylation of Styrene

We report a detailed and full computational investigation on the hydrovinylation reaction of styrene with the Ni(II)-phospholane catalytic system, which was originally presumed to proceed through a cationic mechanism involving a nickel hydride intermediate. The following general features emerge from this study on a specific catalyst complex that was found to give quantitative yield and moderate selectivity: (a) the activation barrier for the initiation (18.8 kcal/mol) is higher than that for the reaction due to a low-lying square-planar pentenyl chelate intermediate originating from a Ni(II)-allyl catalyst precursor. Consequently there is an induction period for the catalysis; (b) the exit of product from the catalyst is via a β-H-transfer step instead of the usual β-H elimination pathway, which has a very high activation energy due to a trans effect of the phospholane ligand; (c) the turnover-limiting and enantio- determining transition state is also the β-H-transfer; (d) because of the absence of a hydride intermediate, the unwanted isomerization of the product is prevented; (e) since the enantio-discrimination is decided at the H-transfer stage itself, the configuration of the product in a catalytic cycle influences the enantioselectivity in the subsequent cycle; (f) the trans effect of the sole strong ligand in the d8 square-planar Ni(II), the stability of the η(3)-benzyl intermediate, and the availability of three coordination sites enable regioselective hydrovinylation over the possible oligomerization/polymerization of the olefin substrates and linear hydrovinylation. This work has also confirmed the previously recognized role of the hemilabile group at various stages in the mechanism.

Phosphoramidite quinaphos‐Type Ligands for Highly Selective Ni‐Catalysed Asymmetric C–C Bond Forming Reactions

AbstractMonodentate quinaphos phosphoramidites bearing different substituents in the 2‐position of the 1,2‐dihydroquinoline backbone were synthesised and characterised. Computational, NMR spectroscopic and X‐ray crystallographic methods were used for the elucidation of the structure in solution and in the solid state. Diastereomerically pure ligands were used in the nickel‐catalysed asymmetric hydrovinylation of styrene as well as in the cycloisomerisation of diethyl diallylmalonate. Enantiomeric excesses up to 91 % for the hydrovinylation reaction and up to 46 % for the cycloisomerisation reaction were obtained, accompanied with unprecedented high activities and regioselectivities. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Synthesis and characterization of palladium(II) complexes with chiral aminophosphine ligands: Catalytic behaviour in asymmetric hydrovinylation. Crystal structure of cis-[PdCl 2(PPh(( R)-NHCHCH 3Ph) 2) 2

Optically active ligands of type Ph 2PNHR (R = ( R)-CHCH 3Ph, ( a); ( R)-CHCH 3Cy, ( b); ( R)-CHCH 3Naph, ( c)) and PhP(NHR) 2 (R = ( R)-CHCH 3Ph, ( d); ( R)-CHCH 3Cy, ( e)) with a stereogenic carbon atom in the R substituent were synthesized. Reaction with [PdCl 2(COD) 2] produced [PdCl 2P 2] ( 1) (P = PhP(NHCHCH 3Ph) 2), whose molecular structure determined by X-ray diffraction showed cis disposition for the ligands. All nitrogen atoms of amino groups adopted S configuration. The new ligands reacted with allylic dimeric palladium compound [Pd(η 3-2-methylallyl)Cl] 2 to gave neutral aminophosphine complexes [Pd(η 3-2-methylallyl)ClP] ( 2a– 2e) or cationic aminophosphine complexes [Pd(η 3-2-methylallyl)P 2]BF 4 ( 3a– 3e) in the presence of the stoichiometric amount of AgBF 4. Cationic complexes [Pd(η 43-2-methylallyl)(NCCH 3)P]BF 4 ( 4a– 4e) were prepared in solution to be used as precursors in the catalytic hydrovinylation of styrene. 31P NMR spectroscopy showed the existence of an equilibrium between the expected cationic mixed complexes 4, the symmetrical cationic complexes [Pd(η 3-2-methylallyl)P 2]BF 4 ( 3) and [Pd(η 3-2-methylallyl)(NCCH 3) 2]BF 4 ( 5) coming from the symmetrization reaction. The extension of the process was studied with the aminophosphines ( a– e) as well as with nonchiral monodentate phosphines (PCy 3 ( f), PBn 3 ( g), PPh 3 ( h), PMe 2Ph ( i)) showing a good match between the extension of the symmetrization and the size of the phosphine ligand. We studied the influence of such equilibria in the hydrovinylation of styrene because the behaviour of catalytic precursors can be modified substantially when prepared ‘ in situ’. While compounds 3 and bisacetonitrile complex 5 were not active as catalysts, the [Pd(η 3-2-methylallyl)(η 2-styrene) 2] + species formed in the absence of acetonitrile showed some activity in the formation of codimers and dimers. Hydrovinylation reaction between styrene and ethylene was tested using catalytic precursors solutions of [Pd(η 3-2-methylallyl)LP]BF 4 ionic species (L = CH 3CN or styrene) showing moderate activity and good selectivity. Better activities but lower selectivities were found when L = styrene. Only in the case of the precursor containing Ph 2PNHCHCH 3Ph ( a) ligand was some enantiodiscrimination (10%) found.

The Mechanism of the Phosphine-Free Palladium-Catalyzed Hydroarylation of Alkynes

The mechanism of the Pd-catalyzed hydroarylation and hydrovinylation reaction of alkynes has been studied by a combination of experimental and theoretical methods (B3LYP), with an emphasis on the phosphine-free version. The regioselectivity of the hydroarylation and hydrovinylation shows unexpected differences, which could be attributed mainly to the higher steric demand of the cyclohexenyl group as compared to the phenyl group. Hydroarylation of alpha,beta-acetylenic carbonyl substrates yields a very unusual anti-Michael selectivity, which is shown to result from reaction of the nonconjugated double bond, leaving the conjugation intact. In all cases were the regioselectivities reproduced by the calculations.

Highly Selective Cobalt-Catalyzed Hydrovinylation of Styrene

The hydrovinylation reaction is a codimerization of a 1,3-diene or vinyl arene and ethene with great potential for fine chemicals and pharmaceuticals. For the first time, enantioselective cobalt-catalyzed hydrovinylations of styrene were achieved with a cobalt-based system bearing a chiral bis(phosphine)amide ligand.

Tunable phosphinite, phosphite and phosphoramidite ligands for the asymmetric hydrovinylation reactions

Only a limited number of ligands have been successfully employed for the Ni-catalyzed asymmetric hydrovinylation reaction. Diarylphosphinites, carrying β-acylamino groups prepared from readily available carbohydrates, in conjunction with highly dissociated counteranions {[(3,5-(CF 3) 2C 6H 3] 4B − or SbF 6 −}, effect the hydrovinylation of vinylarenes under ambient pressure of ethylene with high enantioselectivity. Nitrogen substituents such as –COCF 3 and COPh groups lead to isomerization of the primary products (3-arylbutenes) to Z- and E-2-aryl-2-butenes. In a prototypical synthesis of a 2-arylproionic acid, ( S)-3-(4-bromophenyl)-1-butene (89% ee) has be transformed into ( R)-ibuprofen by Ni-catalyzed cross-coupling with i-BuMgBr, followed by oxidation of the double bond with NaIO 4 and KMnO 4. Asymmetric codimerization of norbonene and ethylene using binaphthol-derived phosphoramidites as ligands gives 1:1, 2:1 or polymeric adducts depending on the relative configurations and nature of the BINAP and amine moieties. With one of the phosphoramidite–Ni complexes, counteranions BAr 4 − [Ar=3,5-(CF 3) 2C 6H 3] and SbF 6 −, which had been used interchangeably in other reactions, give either a 1:1 adduct or a 2:1 adduct, respectively.

The Asymmetric Hydrovinylation Reaction: Ethylene as Carbon Source for the Synthesis of Fine Chemicals

AbstractFor Abstract see ChemInform Abstract in Full Text.

Asymmetric hydrovinylation reaction.

Asymmetric hydrovinylation reaction.

Coordinated olefins as incipient carbocations: catalytic codimerization of ethylene and internal olefins by a dicationic Pt(II)-ethylene complex.

The coordinated ethylene molecule in the dicationic complex [(PNP)Pt(CH2=CH2)](BF4)2 (PNP = 2,6-bis(diphenylphosphinomethyl)pyridine) undergoes nucleophilic attack by free internal alkenes, giving the isolable complexes [(PNP)Pt(CH2=CHCH(Me)CMeRR'](BF4)2 (R, R' = H, Me) and providing a new effective pathway for a chemo- and regio-selective catalytic hydrovinylation reaction.

Tunable ligands for asymmetric catalysis: readily available carbohydrate-derived diarylphosphinites induce high selectivity in the hydrovinylation of styrene derivatives.

Only a limited number of ligands have been successfully employed for the Ni-catalyzed asymmetric hydrovinylation reaction. Diarylphosphonites prepared from readily available carbohydrates in conjunction with a highly dissociated counterion ([3,5-(CF3)2-C6H3)4B]- or SbF6-) effect the hydrovinylation of 4-bromostyrene or 4-isobutylstyrene under ambient pressure of ethylene with the best overall selectivities reported to date for these important substrates. In a prototypical synthesis of a 2-arylpropionic acid, 3-(4-bromophenyl)-1-butene (prepared in 98% isolated yield and 89% ee from 4-bromostyrene) has been transformed into (R)-ibuprofen by Ni-catalyzed cross-coupling with i-BuMgBr, ozonolysis, and subsequent oxidation of the resulting aldehyde.