First Resolution of a Free Fluorophosphane Chiral at Phosphorus

Pabel, Michael; Willis, Anthony C.; Wild, S. Bruce

doi:10.1002/anie.199418351

Cited by 25 publications

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“…Complex 12a reacts with neutral monodentate or chelating ligands to give various cationic derivatives (see Scheme 2) depending on the molar ratio of the reagents. Thus, complex [Pd{py{SCHC(O)Ph}-2}(NCMe)(PPh 3 )]-ClO 4 (13) was obtained by addition of 1 equiv of PPh 3 to a suspension of 12a in acetonitrile, whereas complexes [Pd{py{SCHC(O)Ph}-2}L 2 ]ClO 4 [L ) PPh 3 (14), L 2 ) tmeda, (15), bpy (16)] were prepared by adding solid 12a to a dichloromethane solution containing 2 equiv of PPh 3 or 1 equiv of tmeda or bpy, respectively. If the order of addition of the reagents is reversed, mixtures are obtained containing complexes 14-16 and the above-mentioned products that result when 12a is dissolved in dichloromethane.…”

Section: Slow Addition Of An Acetone Solution Of Py{sch 2 C-(o)mentioning

confidence: 99%

“…Cyclopalladated complexes are becoming increasingly important in organic synthesis. − Chiral cyclopalladated derivatives are being used for optical resolution purposes − and for enantioselective catalysis . Many palladacycles have found use in the preparation of metallomesogens, − and some show antitumor activity. , …”

Section: Introductionmentioning

confidence: 99%

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Multidonor Ligands. 3. Cyclopalladation of py{SCH₂C(O)R}-2 (py-2 = 2-pyridyl, R = Ph, Me, OMe) through a C(sp³)−H Bond Activation

et al. 1999

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[PdCl2(NCPh)2] reacts with R−carbonylmethylenethiopyridines [py{SCH2C(O)R}-2] to give, depending on the substituent R and the reaction conditions, or the coordination complexes [Pd{py{SCH2C(O)R}-2}2Cl2] (R = Ph, Me, OMe). The latter can be doubly deprotonated by a base (Na2CO3 or NaH) to give dicyclometalated complexes These transmetalate one ligand to [PdCl2(NCPh)2] to give which in turn reacts with (Me4N)Cl or with monodentate ligands L or with MeCN in the presence of AgClO4 to give anionic neutral [R = Ph, L = PPh3, py{SCH2C(O)Ph}-2, tBuNC, NH2CH(Me)Ph, pyridine (py), tetrahydrothiophene (tht); R = Me, L = PPh3, py, tht], or cationic (R = Ph, Me, OMe) complexes, respectively. The latter react with PPh3 or with bidentate ligands to give complexes or [L = PPh3, L2 = N,N,N‘,N‘-tetramethylethylenediamine (tmeda) or 2,2‘-bipyridine (bipy)]. The crystal structures of and have been determined.

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Section: Slow Addition Of An Acetone Solution Of Py{sch 2 C-(o)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multidonor Ligands. 3. Cyclopalladation of py{SCH₂C(O)R}-2 (py-2 = 2-pyridyl, R = Ph, Me, OMe) through a C(sp³)−H Bond Activation

et al. 1999

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“…The stereochemistry of the substitution of the fluoride by methoxide in coordinated (±)- 1 has been investigated. A preliminary account of part of this work has been published …”

Section: Introductionmentioning

confidence: 99%

First Resolution of a Free Fluorophosphine Chiral at Phosphorus. Resolution and Reactions of Free and Coordinated (±)-Fluorophenylisopropylphosphine

1996

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The trivalent fluorophosphine (+/-)-PFPh(i-Pr), (+/-)-1, has been prepared by halogen exchange of the corresponding chlorophosphine with sodium fluoride in hot sulfolane. The neat fluorophosphine rapidly decomposes by equilibrium redox disproportionation into PF(3)Ph(i-Pr) and (R,R)/(R,S)-Ph(i-Pr)PPPh(i-Pr), but in benzene, (+/-)-1 has considerable thermodynamic stability. The resolution of (+/-)-1 was achieved by a fractional crystallization of the diastereomers (R,R(P))- and (R,S(P))-chloro[1-[1-(dimethylamino)ethyl]-2-naphthalenyl-C,N](fluorophenylisopropylphosphine)palladium(II), (R,R(P))- and (R,S(P))-5, whereby the less soluble (R,R(P)) diastereomer selectively crystallized in 64% yield in a typical second-order asymmetric transformation. Optically pure (S)-(-)-1, -210 (c 0.59, C(6)H(6)), was liberated from (R,R(P))-5 with (R,S)-1,2-phenylenebis(methylphenylphosphine). The optically active phosphine in benzene racemizes over 6 h without significant redox disproportionation. The methoxyphosphine (+/-)-P(OMe)Ph(i-Pr), (+/-)-9, was also resolved by the method of metal complexation. Thus, fractional crystallization of (R,R(P))- and (R,S(P))-chloro[1-[1-(dimethylamino)ethyl]-2-naphthalenyl-C,N](methoxyphenylisopropylphosphine)palladium(II), (R,R(P))- and (R,S(P))-8, followed by liberation of the respective optically active methoxyphosphines from the separated diastereomers with 1,2-bis(diphenylphosphino)ethane, gave (R)-(+)- and (S)-(-)-9 of 92% and 96% ee, respectively. The barrier to unimolecular inversion for (+/-)-9 was determined to be >82.9 +/- 0.5 kJ mol(-)(1) by variable temperature (1)H NMR spectroscopy. The substitution of fluoride in (R,R(P))-5 by methoxide proceeds with predominant inversion of the configuration at phosphorus to give (R,R(P))- and (R,S(P))-8 with (R,S(P))/(R,R(P)) = (1)/(5). The crystal structures of (R,R(P))-5 and (R,R(P))-8 have been determined: (R,R(P))-5 (C(23)H(28)ClFNPPd) crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 9.967(2) Å, b = 10.998(4) Å, c = 21.324(3) Å, Z = 4, and R = 0.031; (R,R(P))-8 (C(24)H(31)ClNOPPd) crystallizes in the space group P2(1)2(1)2(1) with a = 10.444(3) Å, b = 12.146(3) Å, c = 19.047(2) Å, Z = 4, and R = 0.026.

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“…Crystallization-induced asymmetric transformation (AT) is a promising technique for control of heteroelement configuration . This method is useful in molecules that contain one or more configurationally stable asymmetric carbons in addition to a potentially labile stereogenic heteroatom such as trivalent phosphorus or tetravalent boron . Provided that both epimers at the heteroatom can interconvert on the time scale of crystallization, the diastereomer that corresponds to the more stable crystal lattice can be obtained with extraordinary selectivity simply by allowing solvent to slowly evaporate.…”

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Asymmetric Memory at Labile, Stereogenic Boron: Enolate Alkylation of Oxazaborolidinones

et al. 1999

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Oxazaborolidinones 3, 25, 32, 42, 49, and 53 can be obtained as single diastereomers by crystallization-induced asymmetric transformation (AT). Asymmetric memory is maintained in the derived enolates because the stereogenic boron resists equilibration with achiral, trivalent boron-containing species on the time scale of enolate alkylation with methyl iodide, allyl bromide, or benzyl bromide. Conditions were found for alkylating oxazaborolidinone enolates derived from phenylalanine (5, 33), alanine (18, 26), phenylglycine (43), and valine (54) without significant loss of boron configuration. The phenylglycine-derived oxazaborolidinone alkylation products 44 and 45 slowly undergo boron epimerization at room temperature, and the C-allyl product 44b partially racemizes during hydrolytic cleavage, apparently by a 2-aza-Cope rearrangement. These complications were not encountered with phenylalanine derivatives. Preparatively useful results were obtained with oxazaborolidinones 3 and 32, derived from phenylalanine. AT favors a different boron configuration in the B-naphthyl analogue 32 compared to 3. This provides access to either quasi-enantiomeric enolate 5 or 33 by starting from the same phenylalanine enantiomer.

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First Resolution of a Free Fluorophosphane Chiral at Phosphorus

Cited by 25 publications

References 17 publications

Multidonor Ligands. 3. Cyclopalladation of py{SCH₂C(O)R}-2 (py-2 = 2-pyridyl, R = Ph, Me, OMe) through a C(sp³)−H Bond Activation

Multidonor Ligands. 3. Cyclopalladation of py{SCH₂C(O)R}-2 (py-2 = 2-pyridyl, R = Ph, Me, OMe) through a C(sp³)−H Bond Activation

First Resolution of a Free Fluorophosphine Chiral at Phosphorus. Resolution and Reactions of Free and Coordinated (±)-Fluorophenylisopropylphosphine

Asymmetric Memory at Labile, Stereogenic Boron: Enolate Alkylation of Oxazaborolidinones

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First Resolution of a Free Fluorophosphane Chiral at Phosphorus

Cited by 25 publications

References 17 publications

Multidonor Ligands. 3. Cyclopalladation of py{SCH2C(O)R}-2 (py-2 = 2-pyridyl, R = Ph, Me, OMe) through a C(sp3)−H Bond Activation

Multidonor Ligands. 3. Cyclopalladation of py{SCH2C(O)R}-2 (py-2 = 2-pyridyl, R = Ph, Me, OMe) through a C(sp3)−H Bond Activation

First Resolution of a Free Fluorophosphine Chiral at Phosphorus. Resolution and Reactions of Free and Coordinated (±)-Fluorophenylisopropylphosphine

Asymmetric Memory at Labile, Stereogenic Boron: Enolate Alkylation of Oxazaborolidinones

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Multidonor Ligands. 3. Cyclopalladation of py{SCH₂C(O)R}-2 (py-2 = 2-pyridyl, R = Ph, Me, OMe) through a C(sp³)−H Bond Activation

Multidonor Ligands. 3. Cyclopalladation of py{SCH₂C(O)R}-2 (py-2 = 2-pyridyl, R = Ph, Me, OMe) through a C(sp³)−H Bond Activation