New cyclic phosphonium salts derived from the reaction of phosphine-aldehydes with acid

Mikhailine, Alexandre A.; Lagaditis, Paraskevi O.; Sues, Peter E.; Lough, Alan J.; Morris, Robert H.

doi:10.1016/j.jorganchem.2010.04.016

Cited by 22 publications

(37 citation statements)

References 32 publications

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“…The phosphonium dimer was synthesized by deprotection of diphenylphosphinoacetaldehyde diacetal, in acidic solution. 18 Reaction of the commercially available diphenylphosphine (HPPh2) with potassium hydride (KH) generates the phosphide (KPPh2), which can undergo nucleophilic attack on the protected aldehyde (chloroacetoaldehyde diethyl acetal, ClCH2CH(OEt)2) to give a protected phosphine-aldehyde intermediate. Deprotection of the phosphine-aldehyde diethyl acetals in acidic media gives the desired dimer as a white, air-stable solid in 82% yield.…”

Section: Figure 3 Synthesis Of the Phenyl-substituted Phosphonium Dimermentioning

confidence: 99%

Synthesis and use of an asymmetric transfer hydrogenation catalyst based on iron(II) for the synthesis of enantioenriched alcohols and amines

Zuo

Morris

2015

Nat Protoc

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The catalytic hydrogenation of prochiral ketones and imines is an advantageous approach to the synthesis of enantioenriched alcohols and amines, respectively, which are two classes of compounds that are highly prized in pharmaceutical, fragrance and flavoring chemistry. This hydrogenation reaction is generally carried out using ruthenium-based catalysts. Our group has developed an alternative synthetic route that is based on the environmentally friendlier iron-based catalysis. This protocol describes the three-part synthesis of trans-[amine(imine)diphosphine]chlorocarbonyliron(II) tetrafluoroborate templated by iron salts and starting from commercially available chemicals, which provides the precatalyst for the efficient asymmetric transfer hydrogenation of ketones and imines. The use of the enantiopure (S,S) catalyst to reduce prochiral ketones to the (R)-alcohol in good to excellent yields and enantioenrichment is also detailed, as well as the reduction to the amine in very high yield and enantiopurity of imines substituted at the nitrogen with the N-(diphenylphosphinoyl) group (-P(O)Ph2). Although the best ruthenium catalysts provide alcohols in higher enantiomeric excess (ee) than the iron complex catalyst used in this protocol, they do so on much longer time scales or at higher catalyst loadings. This protocol can be completed in 2 weeks.

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Section: Figure 3 Synthesis Of the Phenyl-substituted Phosphonium Dimermentioning

confidence: 99%

Synthesis and use of an asymmetric transfer hydrogenation catalyst based on iron(II) for the synthesis of enantioenriched alcohols and amines

Zuo

Morris

2015

Nat Protoc

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“…The syntheses of the new iron(II) precatalysts were carried out using routes developed in our lab previously ,,. Complexes ( S,S )‐1 with R′ =Et and ( S,S )‐2 with R′=o‐Tol were synthesized using the enantiopure ( S,S )‐PPh 2 CH 2 CH 2 NHCHPhCHPhNH 2 compound and the phosphonium dimers D1 or D2 , respectively, in two main steps (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Asymmetric Transfer Hydrogenation of Ketones Using New Iron(II) (P‐NH‐N‐P′) Catalysts: Changing the Steric and Electronic Properties at Phosphorus P′

Smith

Prokopchuk

Morris

2017

Israel Journal of Chemistry

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The asymmetric transfer hydrogenation (ATH) of ketones is an efficient method for producing enantioenriched alcohols which are used as intermediates in a variety of industrial processes. Here we report the synthesis of new iron ATH precatalysts (S,S)-[FeBr(CO)(Ph 2 PCH 2 CH 2 NHCHPhCHPhNC = CHCH 2 PR' 2 )][BPh 4 ] (R' = Et, and orthotolyl (o-Tol)) where one of the phosphine groups is modified with small alkyl and large aryl substituents to probe the effect of this change on the activity and selectivity of the catalytic system. A simple reversible equilibrium kinetic model is used to obtain the initial TOF and the inherent enantioselectivity S = k R /k S of these catalysts along with those for the previously reported catalysts with R' = Ph and Cy for the ATH of acetophenone. With an increase in the size of the PR' 2 group, the TOF goes through a maximum at PPh 2 while the S value goes through a maximum of 510 at R' = Cy. The complex with R' = o-Tol starts with a high S value of 200 but is rapidly changed to a second catalyst with an S value of 28. For the reduction of acetophenone to (R)-1-phenylethanol, turnover numbers of up to 5200 and ee up to 98 % were achieved. The chemotherapeutic pharmaceutical precursor (R)-(3',5'-bis(trifluoromethyl))-1-phenylethanol is synthesized in up to 95 % ee. Several other alcohols can be prepared in greater than 90 % ee by choosing the precatalyst with the correctly matched steric properties. A hydride complex derived from the catalyst with R' = Cy is characterized by NMR spectroscopy. It is proposed that low concentration trans-hydride carbonyl complexes with the FeH parallel to the NH of the ligand are the active catalysts in all of these systems.Keywords: homogeneous catalysis · iron catalysis · asymmetric transfer hydrogenation [a] S.

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“…8). In addition, because water instead of base was added to the reaction mixture, an acidic work-up was not needed to generate the phosphonium dimer salts 1b-d. 50,51 With the phosphonium salts readily available, the synthesis of the corresponding iron complexes was carried out. Much like the original phenyl-substituted species derived from 1a, the alkyl variants of the 5,5,5-PNNP ligand could only be generated in a one-pot template reaction in the presence of iron.…”

Section: Stereoelectronic Effectsmentioning

confidence: 99%

“…10, route (a)). 49,50 A drawback of this conven- Fig. 8 Synthesis of alkyl-substituted phosphonium salt precursors in THF at reflux in the presence of water.…”

Section: Stereoelectronic Effectsmentioning

confidence: 99%

“…8 Synthesis of alkyl-substituted phosphonium salt precursors in THF at reflux in the presence of water. 50,51 This journal is © The Royal Society of Chemistry 2014 tional route for synthesizing phosphonium dimers, however, is that it relies on the use of expensive, as well as highly air-sensitive phosphine precursors. The literature procedure for synthesizing the required electron-donating diarylphosphines involves the use of Grignard reagents and diethylphosphite to produce diarylphosphine oxides, which can, in turn, be reduced to diarylphosphines by diisobutylaluminum hydride (DIBAL).…”

Section: Stereoelectronic Effectsmentioning

confidence: 99%

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Rational development of iron catalysts for asymmetric transfer hydrogenation

2014

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The asymmetric reduction of ketones and imines by transfer of hydrogen from isopropanol as the solvent catalyzed by metal complexes is a very useful method for preparing valuable enantioenriched alcohols and amines. Described here is the development of three generations of progressively more active iron catalysts for this transformation. Key features of this process of discovery involved the realization that one carbonyl ligand was needed (as in hydrogenases), the synthesis of modular ligands templated by iron, the elucidation of the mechanisms of catalyst activation and action, as well as the rational synthesis of precursors that lead directly and easily to the species in the catalytic cycle. The discovery that iron, an abundant element that is essential to life, can form catalysts of these hydrogenation reactions is a contribution to green chemistry.

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New cyclic phosphonium salts derived from the reaction of phosphine-aldehydes with acid

Cited by 22 publications

References 32 publications

Synthesis and use of an asymmetric transfer hydrogenation catalyst based on iron(II) for the synthesis of enantioenriched alcohols and amines

Synthesis and use of an asymmetric transfer hydrogenation catalyst based on iron(II) for the synthesis of enantioenriched alcohols and amines

Asymmetric Transfer Hydrogenation of Ketones Using New Iron(II) (P‐NH‐N‐P′) Catalysts: Changing the Steric and Electronic Properties at Phosphorus P′

Rational development of iron catalysts for asymmetric transfer hydrogenation

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