Abstract This chapter reviews the chemistry of phosphiranes, phosphirenes, and their heavier anal... more Abstract This chapter reviews the chemistry of phosphiranes, phosphirenes, and their heavier analogues reported from 2008 to 2018, with focus on the structure of the three-membered rings, synthesis, and reactivity, which is dominated by relief of ring strain. Applications as ligands for transition metals and use in catalysis are also considered.
Tetrahedral main‐group compounds are normally configurationally stable, but P‐epimerization of th... more Tetrahedral main‐group compounds are normally configurationally stable, but P‐epimerization of the chiral phosphiranium cations syn‐ or anti‐[Mes*P(Me)CH2CHPh][OTf] (Mes*=2,4,6‐(t‐Bu)3C6H2) occurred under mild conditions at 60 °C in CD2Cl2, resulting in isomerization to give a syn‐enriched equilibrium mixture. Ion exchange with excess [NBu4][Δ‐TRISPHAT] (Δ‐TRISPHAT=Δ‐P(o‐C6Cl4O2)3) followed by chromatography on silica removed [NBu4][OTf] and gave mixtures of syn‐ and anti‐[Mes*P(Me)CH2CHPh][Δ‐TRISPHAT]⋅x[NBu4][Δ‐TRISPHAT]. NMR spectroscopy showed that isomerization proceeded with epimerization at P and retention at C. DFT calculations are consistent with a mechanism involving P‐C cleavage to yield a hyperconjugation‐stabilized carbocation, pyramidal inversion promoted by σ‐interaction of the P lone pair with the neighboring β‐carbocation, and ring closure with inversion of configuration at P.
Reaction of the enantiomerically enriched P-stereogenic phosphiranes syn-(RP,SC)-Mes*PCH2CH(Ph) (... more Reaction of the enantiomerically enriched P-stereogenic phosphiranes syn-(RP,SC)-Mes*PCH2CH(Ph) (syn-1) and anti-(SP,SC)-Mes*PCH2CH(Ph) (anti-2, Mes* = 2,4,6-(t-Bu)3C6H2) with metal complex precursors gave Au(L)(Cl) (L = 1 (3); L = 2 (4)), trans-ML2Cl2 (L = 1, M = Pd (5), Pt (6)), Pd(η3-C3H5)(L)(Cl) (L = 1 (7)), and trans-RhL2(CO)(Cl) (L = 1 (8); L = 2 (9)); 3, 4, 7, and 9 were crystallographically characterized. Phosphirane coordination resulted in shortening of the P–C bonds and increased bond angles at P, consistent with rehybridization at phosphorus. A comparison of complexes of phenylphosphirane and phenyldimethylphosphine using IR spectra, coupled with DFT studies using electronic decomposition analysis (EDA) and natural orbitals for chemical valence (NOCV), indicated that phosphiranes are slightly poorer σ-donors than the analogous phosphines and that the π-acceptor properties of these ligands are similar. Pauli repulsion, dispersion, and electrostatic attraction are also important factors in deter...
Angewandte Chemie (International ed. in English), Jan 23, 2018
Nucleophilic substitution results in inversion of configuration at the electrophilic carbon cente... more Nucleophilic substitution results in inversion of configuration at the electrophilic carbon center (S 2) or racemization (S 1). The stereochemistry of the nucleophile is rarely considered, but phosphines, which have a high barrier to pyramidal inversion, attack electrophiles with retention of configuration at P. Surprisingly, cyclization of bifunctional secondary phosphine alkyl tosylates proceeded under mild conditions with inversion of configuration at the nucleophile to yield P-stereogenic syn-phosphiranes. DFT studies suggested that the novel stereochemistry results from acid-promoted tosylate dissociation to yield an intermediate phosphenium-bridged cation, which undergoes syn-selective cyclization.
... (b) Collman, JP; Hegedus, LS; Norton, JR; Finke, RG Principles and Applications of Organotran... more ... (b) Collman, JP; Hegedus, LS; Norton, JR; Finke, RG Principles and Applications of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1987. ... Ana García,Julio Gómez, Elena Lalinde, and M. Teresa Moreno. Organometallics 2006 25 (16), 3926-3934. ...
ABSTRACT Catalytic asymmetric alkylation of the bis(secondary phosphines) IsHP(CH2)nPHIs (1a−e, n... more ABSTRACT Catalytic asymmetric alkylation of the bis(secondary phosphines) IsHP(CH2)nPHIs (1a−e, n = 1−5, Is = isityl = 2,4,6-(i-Pr)3C6H2) with benzyl bromide using the base NaOSiMe3 and the catalyst precursor Pt((R,R)-Me-DuPhos)(Ph)(Cl) gave the bis(tertiary phosphines) Is(PhCH2)P(CH2)nP(CH2Ph)Is (2a−e, n = 1−5) via the intermediates Is(PhCH2)P(CH2)nPHIs (4a−e, n = 1−5). The rates of these reactions depended strongly on n, in the order 1a < 1b < 1c ≈ 1d ≈ 1e. The bulkier bis(secondary phosphine) Mes*HP(CH2)2PHMes* (5, Mes* = 2,4,6-(t-Bu)3C6H2) did not undergo catalytic alkylation under these conditions. The alkylation selectivity also depended on n. Alkylation of 1b was meso-selective, while alkylation of 1a,c−e was rac-selective, occurring with similar diastereoselectivity and enantioselectivity for the longer linkers (1c−e). The product ratios suggested that the catalyst controlled the selectivity for 1d,e, while substrate control operated for ethano-bridged 1b, with negative cooperativity. Substrate control also likely occurred for 1a, for which competition from the background alkylation was significant. Analysis of the observed diastereo- and enantioselectivity for Pt-catalyzed alkylation of 1c and the mixed secondary/tertiary phosphine IsHP(CH2)3P(CH2Ph)Is (4c) yielded quantitative information on the selectivity of both P−C bond-forming steps, which was consistent with predominant catalyst control, altered slightly by the influence of the substrate.
Enantioselective tandem alkylation/arylation of primary phosphines with 1-bromo-8-chloromethylnap... more Enantioselective tandem alkylation/arylation of primary phosphines with 1-bromo-8-chloromethylnaphthalene catalyzed by Pt(DuPhos) complexes gave P-stereogenic 1-phosphaacenaphthenes (AcePhos) in up to 74% ee. Diastereoselective formation of four P-C bonds in one pot with bis(primary) phosphines gave C2-symmetric diphosphines, including the o-phenylene derivative DuAcePhos, for which the rac isomer was formed with high enantioselectivity. These reactions, which appear to proceed via an unusual metal-mediated nucleophilic aromatic substitution pathway, yield a new class of heterocycles with potential applications in asymmetric catalysis.
The racemic secondary phosphine PH(Me)(Is) (1, Is = 2,4,6-(i-Pr)3C6H2) was coupled with PhI in th... more The racemic secondary phosphine PH(Me)(Is) (1, Is = 2,4,6-(i-Pr)3C6H2) was coupled with PhI in the presence of NaOSiMe3 and the catalyst Pd((R,R)-Me-Duphos)(Ph)(I) (3) to give P(Ph)(Me)(Is) (2) in up to 78% ee. The intermediate phosphido complex Pd((R,R)-Me-Duphos)(Ph)(P(Me)(Is)) (5a,b) was observed as a mixture of diastereomers by low-temperature 31P NMR. The rate of interconversion of 5a,b by phosphorus inversion is greater than or equal to that of reductive elimination, which suggests that the enantiodetermining step occurs after Pd-P bond formation.
The complexes Pt((R,R)-Me-DuPhos)(Ph)(Cl) (1) and Pt((R,R)-i-Pr-DuPhos)(Ph)(Cl) (2) have been use... more The complexes Pt((R,R)-Me-DuPhos)(Ph)(Cl) (1) and Pt((R,R)-i-Pr-DuPhos)(Ph)(Cl) (2) have been used as catalyst precursors in Pt-catalyzed asymmetric alkylation of secondary phosphines. To investigate structure–reactivity–selectivity relationships in these reactions, analogous complexes with different bis(phospholane) ligands and/or Pt-hydrocarbyl groups were prepared. Treatment of Pt(COD)(R)(Cl) (R = Me, Ph) with BPE or DuPhos ligands gave Pt((R,R)-Me-BPE)(Me)(Cl) (3), Pt((R,R)-Ph-BPE)(Me)(Cl) (5), Pt((R,R)-Ph-BPE)(Ph)(Cl) (6), and Pt((R,R)-i-Pr-DuPhos)(Me)(Cl) (7). However, treatment of Pt(COD)(Me)(Cl) with (R,R)-Me-FerroLANE gave a mixture of products, which were converted upon heating to Pt((R,R)-Me-FerroLANE)(Me)(Cl) (8). A related mixture formed from Pt(COD)(Ph)(Cl) precipitated trans-[Pt((R,R)-Me-FerroLANE)(Ph)(Cl)]n (9T), which on treatment with AgOTf followed by LiCl gave cis-Pt((R,R)-Me-FerroLANE)(Ph)(Cl) (9) as the major product. The reaction of Pt(COD)(Ph)(Cl) with (R,R)-Me-BPE gave the dinucle...
Abstract This chapter reviews the chemistry of phosphiranes, phosphirenes, and their heavier anal... more Abstract This chapter reviews the chemistry of phosphiranes, phosphirenes, and their heavier analogues reported from 2008 to 2018, with focus on the structure of the three-membered rings, synthesis, and reactivity, which is dominated by relief of ring strain. Applications as ligands for transition metals and use in catalysis are also considered.
Tetrahedral main‐group compounds are normally configurationally stable, but P‐epimerization of th... more Tetrahedral main‐group compounds are normally configurationally stable, but P‐epimerization of the chiral phosphiranium cations syn‐ or anti‐[Mes*P(Me)CH2CHPh][OTf] (Mes*=2,4,6‐(t‐Bu)3C6H2) occurred under mild conditions at 60 °C in CD2Cl2, resulting in isomerization to give a syn‐enriched equilibrium mixture. Ion exchange with excess [NBu4][Δ‐TRISPHAT] (Δ‐TRISPHAT=Δ‐P(o‐C6Cl4O2)3) followed by chromatography on silica removed [NBu4][OTf] and gave mixtures of syn‐ and anti‐[Mes*P(Me)CH2CHPh][Δ‐TRISPHAT]⋅x[NBu4][Δ‐TRISPHAT]. NMR spectroscopy showed that isomerization proceeded with epimerization at P and retention at C. DFT calculations are consistent with a mechanism involving P‐C cleavage to yield a hyperconjugation‐stabilized carbocation, pyramidal inversion promoted by σ‐interaction of the P lone pair with the neighboring β‐carbocation, and ring closure with inversion of configuration at P.
Reaction of the enantiomerically enriched P-stereogenic phosphiranes syn-(RP,SC)-Mes*PCH2CH(Ph) (... more Reaction of the enantiomerically enriched P-stereogenic phosphiranes syn-(RP,SC)-Mes*PCH2CH(Ph) (syn-1) and anti-(SP,SC)-Mes*PCH2CH(Ph) (anti-2, Mes* = 2,4,6-(t-Bu)3C6H2) with metal complex precursors gave Au(L)(Cl) (L = 1 (3); L = 2 (4)), trans-ML2Cl2 (L = 1, M = Pd (5), Pt (6)), Pd(η3-C3H5)(L)(Cl) (L = 1 (7)), and trans-RhL2(CO)(Cl) (L = 1 (8); L = 2 (9)); 3, 4, 7, and 9 were crystallographically characterized. Phosphirane coordination resulted in shortening of the P–C bonds and increased bond angles at P, consistent with rehybridization at phosphorus. A comparison of complexes of phenylphosphirane and phenyldimethylphosphine using IR spectra, coupled with DFT studies using electronic decomposition analysis (EDA) and natural orbitals for chemical valence (NOCV), indicated that phosphiranes are slightly poorer σ-donors than the analogous phosphines and that the π-acceptor properties of these ligands are similar. Pauli repulsion, dispersion, and electrostatic attraction are also important factors in deter...
Angewandte Chemie (International ed. in English), Jan 23, 2018
Nucleophilic substitution results in inversion of configuration at the electrophilic carbon cente... more Nucleophilic substitution results in inversion of configuration at the electrophilic carbon center (S 2) or racemization (S 1). The stereochemistry of the nucleophile is rarely considered, but phosphines, which have a high barrier to pyramidal inversion, attack electrophiles with retention of configuration at P. Surprisingly, cyclization of bifunctional secondary phosphine alkyl tosylates proceeded under mild conditions with inversion of configuration at the nucleophile to yield P-stereogenic syn-phosphiranes. DFT studies suggested that the novel stereochemistry results from acid-promoted tosylate dissociation to yield an intermediate phosphenium-bridged cation, which undergoes syn-selective cyclization.
... (b) Collman, JP; Hegedus, LS; Norton, JR; Finke, RG Principles and Applications of Organotran... more ... (b) Collman, JP; Hegedus, LS; Norton, JR; Finke, RG Principles and Applications of Organotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1987. ... Ana García,Julio Gómez, Elena Lalinde, and M. Teresa Moreno. Organometallics 2006 25 (16), 3926-3934. ...
ABSTRACT Catalytic asymmetric alkylation of the bis(secondary phosphines) IsHP(CH2)nPHIs (1a−e, n... more ABSTRACT Catalytic asymmetric alkylation of the bis(secondary phosphines) IsHP(CH2)nPHIs (1a−e, n = 1−5, Is = isityl = 2,4,6-(i-Pr)3C6H2) with benzyl bromide using the base NaOSiMe3 and the catalyst precursor Pt((R,R)-Me-DuPhos)(Ph)(Cl) gave the bis(tertiary phosphines) Is(PhCH2)P(CH2)nP(CH2Ph)Is (2a−e, n = 1−5) via the intermediates Is(PhCH2)P(CH2)nPHIs (4a−e, n = 1−5). The rates of these reactions depended strongly on n, in the order 1a < 1b < 1c ≈ 1d ≈ 1e. The bulkier bis(secondary phosphine) Mes*HP(CH2)2PHMes* (5, Mes* = 2,4,6-(t-Bu)3C6H2) did not undergo catalytic alkylation under these conditions. The alkylation selectivity also depended on n. Alkylation of 1b was meso-selective, while alkylation of 1a,c−e was rac-selective, occurring with similar diastereoselectivity and enantioselectivity for the longer linkers (1c−e). The product ratios suggested that the catalyst controlled the selectivity for 1d,e, while substrate control operated for ethano-bridged 1b, with negative cooperativity. Substrate control also likely occurred for 1a, for which competition from the background alkylation was significant. Analysis of the observed diastereo- and enantioselectivity for Pt-catalyzed alkylation of 1c and the mixed secondary/tertiary phosphine IsHP(CH2)3P(CH2Ph)Is (4c) yielded quantitative information on the selectivity of both P−C bond-forming steps, which was consistent with predominant catalyst control, altered slightly by the influence of the substrate.
Enantioselective tandem alkylation/arylation of primary phosphines with 1-bromo-8-chloromethylnap... more Enantioselective tandem alkylation/arylation of primary phosphines with 1-bromo-8-chloromethylnaphthalene catalyzed by Pt(DuPhos) complexes gave P-stereogenic 1-phosphaacenaphthenes (AcePhos) in up to 74% ee. Diastereoselective formation of four P-C bonds in one pot with bis(primary) phosphines gave C2-symmetric diphosphines, including the o-phenylene derivative DuAcePhos, for which the rac isomer was formed with high enantioselectivity. These reactions, which appear to proceed via an unusual metal-mediated nucleophilic aromatic substitution pathway, yield a new class of heterocycles with potential applications in asymmetric catalysis.
The racemic secondary phosphine PH(Me)(Is) (1, Is = 2,4,6-(i-Pr)3C6H2) was coupled with PhI in th... more The racemic secondary phosphine PH(Me)(Is) (1, Is = 2,4,6-(i-Pr)3C6H2) was coupled with PhI in the presence of NaOSiMe3 and the catalyst Pd((R,R)-Me-Duphos)(Ph)(I) (3) to give P(Ph)(Me)(Is) (2) in up to 78% ee. The intermediate phosphido complex Pd((R,R)-Me-Duphos)(Ph)(P(Me)(Is)) (5a,b) was observed as a mixture of diastereomers by low-temperature 31P NMR. The rate of interconversion of 5a,b by phosphorus inversion is greater than or equal to that of reductive elimination, which suggests that the enantiodetermining step occurs after Pd-P bond formation.
The complexes Pt((R,R)-Me-DuPhos)(Ph)(Cl) (1) and Pt((R,R)-i-Pr-DuPhos)(Ph)(Cl) (2) have been use... more The complexes Pt((R,R)-Me-DuPhos)(Ph)(Cl) (1) and Pt((R,R)-i-Pr-DuPhos)(Ph)(Cl) (2) have been used as catalyst precursors in Pt-catalyzed asymmetric alkylation of secondary phosphines. To investigate structure–reactivity–selectivity relationships in these reactions, analogous complexes with different bis(phospholane) ligands and/or Pt-hydrocarbyl groups were prepared. Treatment of Pt(COD)(R)(Cl) (R = Me, Ph) with BPE or DuPhos ligands gave Pt((R,R)-Me-BPE)(Me)(Cl) (3), Pt((R,R)-Ph-BPE)(Me)(Cl) (5), Pt((R,R)-Ph-BPE)(Ph)(Cl) (6), and Pt((R,R)-i-Pr-DuPhos)(Me)(Cl) (7). However, treatment of Pt(COD)(Me)(Cl) with (R,R)-Me-FerroLANE gave a mixture of products, which were converted upon heating to Pt((R,R)-Me-FerroLANE)(Me)(Cl) (8). A related mixture formed from Pt(COD)(Ph)(Cl) precipitated trans-[Pt((R,R)-Me-FerroLANE)(Ph)(Cl)]n (9T), which on treatment with AgOTf followed by LiCl gave cis-Pt((R,R)-Me-FerroLANE)(Ph)(Cl) (9) as the major product. The reaction of Pt(COD)(Ph)(Cl) with (R,R)-Me-BPE gave the dinucle...
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