Phosphine as a Reducing Agent

Buckler, Sheldon A.; Doll, Lois; Lind, Frank K.; Epstein, Martin

doi:10.1021/jo01050a026

Cited by 49 publications

(15 citation statements)

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“…If initiation mechanism 2 is operative, then • CF 3 could be generated by irradiating CF 3 I solutions containing electron donors other than Au(I), such as phosphines (Scheme 3 ). 24 Indeed, irradiation of PMe 3 or PCy 3 in the presence of CF 3 I results in formation of [Me 3 P-CF 3 ]I ( 10a , 2 J P–F = 63 Hz) or [Cy 3 P-CF 3 ]I ( 10b, 2 J P–F = 42 Hz); 25 neither reaction proceeds in the dark. Consistent with quenching of [CF 3 I]* by Au(III), the oxidation of PCy 3 in THF stalls at roughly 45% conversion (by 31 P NMR) in the presence of 25 mol % Au(III) complex 3a .…”

Section: Resultsmentioning

confidence: 99%

Photoinitiated Oxidative Addition of CF₃I to Gold(I) and Facile Aryl-CF₃ Reductive Elimination

2014

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Herein we report the mechanism of oxidative addition of CF3I to Au(I), and remarkably fast Caryl–CF3 bond reductive elimination from Au(III) cations. CF3I undergoes a fast, formal oxidative addition to R3PAuR′ (R = Cy, R′ = 3,5-F2-C6H4, 4-F-C6H4, C6H5, 4-Me-C6H4, 4-MeO-C6H4, Me; R = Ph, R′ = 4-F-C6H4, 4-Me-C6H4). When R′ = aryl, complexes of the type R3PAu(aryl)(CF3)I can be isolated and characterized. Mechanistic studies suggest that near-ultraviolet light (λmax = 313 nm) photoinitiates a radical chain reaction by exciting CF3I. Complexes supported by PPh3 undergo reversible phosphine dissociation at 110 °C to generate a three-coordinate intermediate that undergoes slow reductive elimination. These processes are quantitative and heavily favor Caryl–I reductive elimination over Caryl–CF3 reductive elimination. Silver-mediated halide abstraction from all complexes of the type R3PAu(aryl)(CF3)I results in quantitative formation of Ar–CF3 in less than 1 min at temperatures as low as −10 °C.

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Section: Resultsmentioning

confidence: 99%

Photoinitiated Oxidative Addition of CF₃I to Gold(I) and Facile Aryl-CF₃ Reductive Elimination

2014

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“…For example, the reduction of nitro compounds in the presence of an excessive amount of reducing agent,11a the classic coupling reaction of diazo salts with aromatic compounds at low temperature,11b and the aerobic oxidative dehydrogenation of aryl amines in the presence of a transition‐metal catalyst 11c–d. Although the established methodologies have been successfully applied in the synthesis of azo compounds, the restricted reaction conditions, limited substrate scope, and the formation of complex by‐products are undesirable 11a–b. It is worth noting that the synthesis of sterically hindered ortho ‐substituted azo compounds is also a big challenge, and is a reaction that has been little studied thus far.…”

Section: Methodsmentioning

confidence: 99%

A Highly Efficient Palladium‐Catalyzed Decarboxylative ortho‐Acylation of Azobenzenes with α‐Oxocarboxylic Acids: Direct Access to Acylated Azo Compounds

Tan

et al. 2013

Chemistry A European J

112

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“…We also note that alkyl phosphines are generally stable to hydrolysis. Phosphine itself (Buckler et al, 1962)-and more easily handled soluble solids such as tributyl phosphine (Sweetman and Maclaren, 1966) or tris(2-carboxyethyl) phosphine (Burns et al, 1991)-is widely used in aqueous solution as a specific reductant (Sweetman and Maclaren, 1966). Water-soluble and stable phosphine derivatives have been developed as ligands for metal catalysts-the phosphines themselves are stable in water as well as the metal complexes they form (Katti et al, 1999;Pinault and Bruce, 2003).…”

Section: Stability and Reactivity Of Trivalent Phosphorus Compoundsmentioning

confidence: 99%

Trivalent Phosphorus and Phosphines as Components of Biochemistry in Anoxic Environments

Bains¹,

Petkowski

Sousa-Silva

et al. 2019

Astrobiology

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Phosphorus is an essential element for all life on Earth, yet trivalent phosphorus (e.g., in phosphines) appears to be almost completely absent from biology. Instead phosphorus is utilized by life almost exclusively as phosphate, apart from a small contingent of other pentavalent phosphorus compounds containing structurally similar chemical groups. In this work, we address four previously stated arguments as to why life does not explore trivalent phosphorus: (1) precedent (lack of confirmed instances of trivalent phosphorus in biochemicals suggests that life does not have the means to exploit this chemistry), (2) thermodynamic limitations (synthesizing trivalent phosphorus compounds is too energetically costly), (3) stability (phosphines are too reactive and readily oxidize in an oxygen (O 2)-rich atmosphere), and (4) toxicity (the trivalent phosphorus compounds are broadly toxic). We argue that the first two of these arguments are invalid, and the third and fourth arguments only apply to the O 2-rich environment of modern Earth. Specifically, both the reactivity and toxicity of phosphines are specific to aerobic life and strictly dependent on O 2-rich environment. We postulate that anaerobic life persisting in anoxic (O 2-free) environments may exploit trivalent phosphorus chemistry much more extensively. We review the production of trivalent phosphorus compounds by anaerobic organisms, including phosphine gas and an alkyl phosphine, phospholane. We suggest that the failure to find more such compounds in modern terrestrial life may be a result of the strong bias of the search for natural products toward aerobic organisms. We postulate that a more thorough identification of metabolites of the anaerobic biosphere could reveal many more trivalent phosphorus compounds. We conclude with a discussion of the implications of our work for the origin and early evolution of life, and suggest that trivalent phosphorus compounds could be valuable markers for both extraterrestrial life and the Shadow Biosphere on Earth.

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Phosphine as a Reducing Agent

Cited by 49 publications

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Photoinitiated Oxidative Addition of CF₃I to Gold(I) and Facile Aryl-CF₃ Reductive Elimination

Photoinitiated Oxidative Addition of CF₃I to Gold(I) and Facile Aryl-CF₃ Reductive Elimination

A Highly Efficient Palladium‐Catalyzed Decarboxylative ortho‐Acylation of Azobenzenes with α‐Oxocarboxylic Acids: Direct Access to Acylated Azo Compounds

Trivalent Phosphorus and Phosphines as Components of Biochemistry in Anoxic Environments

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Phosphine as a Reducing Agent

Cited by 49 publications

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Photoinitiated Oxidative Addition of CF3I to Gold(I) and Facile Aryl-CF3 Reductive Elimination

Photoinitiated Oxidative Addition of CF3I to Gold(I) and Facile Aryl-CF3 Reductive Elimination

A Highly Efficient Palladium‐Catalyzed Decarboxylative ortho‐Acylation of Azobenzenes with α‐Oxocarboxylic Acids: Direct Access to Acylated Azo Compounds

Trivalent Phosphorus and Phosphines as Components of Biochemistry in Anoxic Environments

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Photoinitiated Oxidative Addition of CF₃I to Gold(I) and Facile Aryl-CF₃ Reductive Elimination

Photoinitiated Oxidative Addition of CF₃I to Gold(I) and Facile Aryl-CF₃ Reductive Elimination