An efficient procedure for the synthesis of C-chiral bisphosphines

McKinstry, Lydia; Livinghouse, Tom

doi:10.1016/0040-4020(95)00390-t

Cited by 111 publications

(54 citation statements)

References 23 publications

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“…For the cyclohexyl (Cy) series (1,4,5,6; n = 0, 1, 2, 3 respectively; Figure 1) the equilibrium constants were also determined by 11 B{ 1 H} NMR analysis of the kinetics of the reverse reaction in which borane is transferred from the quinuclidine adduct 3 to the phosphine (Table 1). The effect of sequentially replacing the phenyl groups by cyclohexyl groups is a strong and progressive attenuation of both the rate (k) and favourability (K) of borane transfer from P-to-N.…”

Section: Effect Of Phosphine Substituentsmentioning

confidence: 99%

“…[5] However, the deprotection step can be more problematic, and a number of alternative strategies to achieve this have been reported. [6][7][8][9] Nonetheless, the most commonly applied procedure is still the use of an amine, [3,[10][11][12][13][14][15] which acts as a competing Lewis base to generate the free phosphine R 3 P, and the corresponding amine-borane (R 3 N·BH 3 ) species. A large variety of amines, stoichiometry, solvent, and reaction temperatures have been reported, with some conditions taking several days to reach acceptable levels of conversion.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism of Phosphine Borane Deprotection with Amines: The Effects of Phosphine, Solvent and Amine on Rate and Efficiency

Lloyd‐Jones

Taylor

2015

Chemistry A European J

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The kinetics of borane transfer from simple tertiary phosphine borane adducts to a wide range of amines have been determined. All data obtained, including second-order kinetics, lack of cross-over, and negative entropies of activation for reaction of triphenylphosphine borane with quinuclidine and triethylamine, are consistent with a direct (SN 2-like) transfer process, rather than a dissociative (SN 1-like) process. The identities of the amine, phosphine, and solvent all impact substantially on the rate (k) and equilibrium (K) of the transfer, which in some cases vary by many orders of magnitude. P-to-N transfer is more efficient with cyclic amines in apolar solvents due to reduced entropic costs and ground-state destabilisation. Taken as a whole, the data allow informed optimisation of the deprotection step from the stand-point of rate, or synthetic convenience. In all cases, both reactants should be present at high initial concentration to gain kinetic benefit from the bimolecularity of the process. Ultimately, the choice of amine is dictated by the identity of the phosphine borane complex. Aryl-rich phosphine boranes are sufficiently reactive to allow use of diethylamine or pyrrolidine as a volatile low polarity solvent and reactant, whereas more alkyl-rich phosphines benefit from the use of more reactive amines, such as 1,4-diaza[2.2.2]bicyclooctane (DABCO), in apolar solvents at higher temperatures.

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Section: Effect Of Phosphine Substituentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanism of Phosphine Borane Deprotection with Amines: The Effects of Phosphine, Solvent and Amine on Rate and Efficiency

Lloyd‐Jones

Taylor

2015

Chemistry A European J

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“…[20] As shown in Scheme 3, the reaction of 7 with DABCO afforded the corresponding polymer 8 in 80% isolated yield. The reaction of 8 with PdCl 2 (cod) (cod ¼ 1,5-cyclooctadiene) in CH 2 Cl 2 gave polymer complex 8-Pd in 45% isolated yield (Scheme 3).…”

Section: Resultsmentioning

confidence: 98%

Synthesis of Optically Active Polymer with P‐Stereogenic Phosphine Units

Morisaki¹,

Suzuki²,

Imoto³

et al. 2010

Macromol. Rapid Commun.

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Optically active polymer containing P-stereogenic bisphosphine as a repeating unit in the main was successfully synthesized. A coordinated borane on the phosphorus atom could be completely removed by an organic base under mild condition, and the successive reaction with Pd afforded the corresponding polymer complex. The chirality of P-stereogenic centers was transferred to the m-phenylene-ethynylene linkers by complexation because of the prohibition of the rotary motion of the bisphosphine-Pd unit.

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“…The two main methods currently used to deprotect phosphanes from their borane derivatives [18] are through displacement of the borane group with an amine (diethylamine, morpholine, or DABCO) [19] or by an acid treatment with methanesulfonic acid, trifluoromethanesulfonic acid, or tetrafluoroboric acid, followed by a basic treatment. [20] Deprotection of the phosphinite-boranes 8 with amines was not convenient, since it required a filtration through silica gel to remove the amine-borane complex formed. A method that does not necessitate an exposure to silica gel was then preferred; decoordination of the borane was realized by treatment of the phosphinite-borane adduct with an amino-grafted resin for an appropriate time, followed by filtration under argon to afford the phosphinite in a quanti-tative yield.…”

Section: Resultsmentioning

confidence: 99%