A chiral diphosphine containing hemilabile ether donor groups and its use in rhodium asymmetric hydroboration of styrene

Ruiz, José Luis; Flor, Teresa; Bayón, J. Carles

doi:10.1016/s1387-7003(99)00128-8

Cited by 12 publications

(5 citation statements)

References 5 publications

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“…In recent years special attention has been paid to the preparation and coordination of hemilabile P , O -donor ligands and, in particular, to phosphinoether compounds . Potential P , N -donor molecules, although less frequently used, have received increased attention in the past few years as hemilabile ligands. , An important application of complexes with hemilabile ligands is in catalysis, and several different processes have been analyzed. 5a, Theoretical studies concerned with this application have been performed 5a, On the other hand, the potentially hemilabile P , N ligand 2-( diphenylphosphino)-1-methylimidazole, dpim (see Chart ), has been studied very little.…”

Section: Introductionmentioning

confidence: 99%

Ruthenium Arene Derivatives with PN Hemilabile Ligands. P−C Cleavage and Phosphine to Phosphinite Transformation

et al. 2004

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Complexes of formula [RuCl 2 (arene)(κ 1 -dpim)] (dpim ) 2-(diphenylphosphino)-1-methylimidazole) (arene ) p-cymene, 1a; C 6 H 6 , 1b) were prepared by the reaction of [RuCl 2 (pcymene)] 2 or [RuCl 2 (C 6 H 6 )(CH 3 CN)] with dpim. Complexes 1a and 1b were structurally characterized by NMR spectroscopy and X-ray diffraction. The reaction of these precursors with BF 4salts led, in dichloromethane, to cationic complexes of formula [RuCl(arene)(κ 2dpim)]BF 4 (arene ) p-cymene, 2a; C 6 H 6 , 2b). However, in methanol the products were unexpected phosphinite derivatives of the type [RuCl(arene)(HImMe){κ 1 -PPh 2 (OMe)}]A (A ) BF 4 , arene ) p-cymene, 3a; C 6 H 6 , 3b; A ) BPh 4 , arene ) p-cymene, 3d) (ImMe ) methylimidazole). This transformation implies the existence of an easy P-C bond cleavage and phosphine functionalization with methanol at room temperature. The precursors 1a,b or the analogous derivative with 2-(diphenylphosphino)pyridine (PPh 2 py), [RuCl 2 (p-cymene)-(κ 1 -PPh 2 py)], 1c, reacted with HBF 4 to give cationic derivatives by protonation of the imidazole or the pyridine fragment, [RuCl 2 (arene)(κ 1 -PNH)]BF 4 (PNH ) dpimH, arene ) p-cymene, 4a; C 6 H 6 , 4b; PNH ) PPh 2 pyH, arene ) p-cymene, 4c). In these compounds the existence of an asymmetric and bifurcated hydrogen bond NH‚‚‚Cl 2 has been structurally determined (even by X-ray studies for 4a,b). Complexes 2a and 4a also yield the corresponding and analogous phosphinite derivatives in the presence of methanol-d 4 but at a markedly slower rate. NMR and spectrophotometric studies provided information concerning the formation of the phosphinite derivatives. It was concluded that the phosphine is not functionalized if it is not coordinated and that, very probably, a methanol solvatesintermediate between 1a and 2asparticipates in the P-C bond cleavage and allows the aforementioned transformation. Some preliminary catalytic tests involving the transfer hydrogenation of cyclohexanone and the hydrogenation of phenylacetylene have also been carried out.

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Section: Introductionmentioning

confidence: 99%

Ruthenium Arene Derivatives with PN Hemilabile Ligands. P−C Cleavage and Phosphine to Phosphinite Transformation

et al. 2004

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“…Included in the former class is the C 2 -symmetric diphosphine (45) from the group of Flor (Figure 3.2 ) [46] .…”

Section: Chiral P P Ligandsmentioning

confidence: 99%

The Development and Application of Rhodium‐Catalyzed Hydroboration of Alkenes

Coyne

Guiry

2008

Modern Reduction Methods

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3.1 IntroductionHydroboration, the addition of a boron -hydrogen bond across an unsaturated moiety, was fi rst discovered by H. C. Brown in 1956 [1] . Usually the reaction does not require a catalyst and the borane reagent, most commonly diborane (B 2 H 6 ) or a borane adduct (BH 3 · THF), reacts rapidly at room temperature to afford, after oxidation, the anti -Markovnikov alkene hydration product. However, when the boron of the hydroborating agent is bonded to heteroatoms, as is the case in catecholborane (1,3,2 -benzodioxaborole) the electron density at boron is increased and elevated temperatures are needed for hydroboration to occur [2,3] .The development of a catalytic hydroboration process was aided by the observation of Kono and Ito in 1975 that Wilkinson ' s catalyst [Rh(PPh 3 ) 3 Cl] undergoes oxidative addition when treated with catecholborane (2) , Scheme 3.1 [4] . Subsequently, Westcott et al. reported the isolation of the oxidative addition adduct with the tri -isopropylphosphine derivative and its characterization by X -ray crystallography [5] . However, it was another decade before the idea of developing a rhodiumcatalyzed olefi n hydroboration process came to fruition with the fi rst examples reported by M ä nnig and N ö th [6] .The conversion of an alkene (1) into an organoborane intermediate (3) has made this a valuable synthetic technique, particularly since the development of enantioselective variants [7, 8] . They serve as synthons for numerous functional groups [9] and are often subject to a consecutive carbon -oxygen [10] , carbon -carbon [11 -13] boron -carbon [14] , boron -chlorine [5] , carbon -nitrogen [15] and other bondforming reactions, Scheme 3.2 . These and other approaches toward extending the synthetic scope of catalytic asymmetric hydroboration have been the subject of recent excellent reviews [16 -18] . Many metals including nickel [19] , ruthenium [20] , iridium [21] , lanthanum [22] , titanium [23] and zirconium [24] have been employed in this transformation with varying degrees of success, although rhodium has remained the metal of choice for transition metal hydroboration.

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“…Included in the former class is the C 2 -symmetrical diphosphine 55, Figure 6, from the group of Flor. [97] This ligand may be regarded as a diphosphine containing two intramolecular solvent molecules, due to the two hemilabile ether donor groups. The cationic Rh(I) complex of (R,R)-55 was tested in the asymmetric hydroboration of styrene (38) with catecholborane (1), at both 20 8C and À 25 8C.…”

Section: Chiral Pp Ligandsmentioning

confidence: 99%

The Development of Enantioselective Rhodium-Catalysed Hydroboration of Olefins

Carroll

O’Sullivan

Guiry

2005

Advanced Synthesis & Catalysis

327

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Rhodium-catalysed enantioselective hydroboration of olefins is a valuable synthetic transformation, typically employing a chiral catalyst and an achiral borane source. The pertinent chemo-, regio-and enantioselectivity issues of this reaction are discussed. However, the main emphasis of this review is on the evolution of catalytic asymmetric hydroboration. This has primarily relied upon the development and application of chiral bidentate P,P and P,N ligands which have exhibited varying degrees of success in this transformation.

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A chiral diphosphine containing hemilabile ether donor groups and its use in rhodium asymmetric hydroboration of styrene

Cited by 12 publications

References 5 publications

Ruthenium Arene Derivatives with PN Hemilabile Ligands. P−C Cleavage and Phosphine to Phosphinite Transformation

Ruthenium Arene Derivatives with PN Hemilabile Ligands. P−C Cleavage and Phosphine to Phosphinite Transformation

The Development and Application of Rhodium‐Catalyzed Hydroboration of Alkenes

The Development of Enantioselective Rhodium-Catalysed Hydroboration of Olefins

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