Tertiary phosphane

The versatility of tertiary phosphane ligands in coordination and organometallic chemistry. R. Mason and D. W. Meek, Angew. Chem., Int. Ed. Engl., 1978,17,183-194 (138). 

Barron et al. report the synthesis of several adducts of tertiary phosphanes with trimethyl aluminum, Eq. (2) [34]. 

In a similar way to the aminolysis of the P-N bond mentioned above (Scheme 9), alcoholysis of phosphinous amides leads to the alkyl esters of the respective phosphinous acids [30, 121]. This reaction occurs with inversion of the absolute configuration of the phosphorus atom, and has been used in a synthetic sequence leading to optically active tertiary phosphanes 22 [122] (Scheme 23). 

Trifluorophosphane can behave as a /x3 donor towards a triangular palladium core.559,360 The symmetrically bridging / -coordination mode has little precedent for tertiary ligands based on Group 15 atoms. The synthesis of a Pd1 dimer featuring a strongly bonded symmetrically bridging /i2-phosphole unit, which is the first example of this coordination mode for a tertiary phosphane, has been reported.561... 

Based on nucleophilic addition, racemic allenyl sulfones were partially resolved by reaction with a deficiency of optically active primary or secondary amines [243]. The reversible nucleophilic addition of tertiary amines or phosphanes to acceptor-substituted allenes can lead to the inversion of the configuration of chiral allenes. For example, an optically active diester 177 with achiral groups R can undergo a racemization (Scheme 7.29). A 4 5 mixture of (M)- and (P)-177 with R = (-)-l-menthyl, obtained through synthesis of the allene from dimenthyl 1,3-acetonedicar-boxylate (cf. Scheme 7.18) [159], furnishes (M)-177 in high diastereomeric purity in 90% yield after repeated crystallization from pentane in the presence of catalytic amounts of triethylamine [158], Another example of a highly elegant epimerization of an optically active allene based on reversible nucleophilic addition was published by Marshall and Liao, who were successful in the transformation 179 — 180 [35], Recently, Lu et al. published a very informative review on the reactions of electron-deficient allenes under phosphane catalysis [244]. 

Hierso et al reported a copper-free, Sonogashira reaction for a number of activated and deactivated aryl halides with alkyl-/aryl acetylenes and using a variety of metallic precursors, bases and tertiary phosphanes in [bmim][BF4]. They found that a combination of [Pd(/7 -C3H5)Cl]2/PPh3 with 1 % pyrrolidine in the absence of copper showed the highest activity. 

Besides a considerable number of chiral Wilkinson-catalysts prepared from chiral a-hydroxy acids 33), carbohydrates 34), stereoids 35), and ferrocenylphosphines 36), many functionalized chiral hiphosphanes based on amino acids have also been developed. The first optically active tertiary phosphane was synthesized in 1961 by Horner et al.37). 

The electrochemical oxidation of tertiary phosphanes, R3P, can be carried out with a platinum electrode in acetonitrile with the addition of pentylammonium fluoride and with the electrolyte tetraethyl ammonium tetrafluoroborate.65 The observed product is the trialkyldi-fluoro-25-phosphane R3PF2. The electrolysis is carried out in a galvanostatic mode with a current density from 3.3 to 6.7 mA cm-2. The anodic oxidation may be represented by the following equation ... 

The reaction of PH3 with Me2N(CH2)2Cl in superbasic media (KOH/ DMSO) was investigated. The tertiary phosphane, upon protonation, affords the extremely water-soluble ligand P[(CH2)2NHMe2]3 Cl3 (solubility 1450 g/1000 ml of water at room temperature) (41). Cationic guanidino-phosphanes (42) and tertiary arylphosphanes containing one or two benzylic amino groups have also been synthesized (43). 

Usually, the catalyst is prepared in situ from palladium(II) salts, a tertiary phosphane, and a base (e.g., K2C03). Both inter- and intramolecular couplings have been investigated (113). Pioneering work in this area was done by Bumagin et al. (114), and several groups are working on this subject today. The most recent publications are cited here. 

In this lecture some new routes to phosphorus-carbon compounds with P-C multiple bonds, found in connection with our investigations on reactions of tertiary phosphanes with chlorinated carbon compounds, such as tetrachloromethane, hexachloroethane, phosgene, and isocyanide dichlorides are reported. Furthermore some stereochemical problems concerning this type of compound will be discussed. 

Fell B, Leckel D, Schobben C (1995) Micellar two phase-hydroformylation of multiple unsaturated fatty substances with water soluble rhodium carbonyl/tertiary phosphane complex catalyst systems. Fett Wiss Technol 97 219-228... 

R Appel, Tertiary Phosphane/Tetrachloromethane, a Versatile Reagent for Chlorination, Dehydration, and P-N Linkage, Angew. Chem. Int. Ed. Engl. 1975, 14, 801-811. 

Tellurocyanates converted tertiary phosphanes to phosphane tellurides1,2. The equilibrium constant for this reaction varies with the nature of the groups bonded to phosphorus2. 

X. Phosphonium Allenide Complexes by Addition of Tertiary Phosphanes... 

Reactions of carbene complexes with phosphorous compounds are topics of current research.164-167 (l-Alkynyl)carbene complexes (CO)5M= C(OEt) —C=CR 1 (M = Cr, W R = Ph, r-Bu, SiMe3) readily add tertiary phosphanes PPhR2 (R = Ph, Me) and form stable zwitterionic phosphonium allenide complexes (CO)5M —C(OEt)=C=C(R)—P+PhR2 145, which have been characterized by X-ray diffraction (Scheme 57).55 In previous studies on Michael-type additions of nitrogen and oxygen nucleophiles to (l-alkynyl)carbene complexes 1, zwitterionic allenide complexes of type 145 have been postulated as intermediates.21,23,503 62 112,168,169 Unambiguous structural evidence of the tendency to form such intermediates is given by isolation of a stable zwitterionic adduct, such as compound 145. Zwitterionic... 

The majority of the publications in the field of oxidative addition of HFA to tertiary phosphanes deal with the formation and properties of l,3,2-A -dioxaphospholanes 57 (60,61). These compounds are generally stable when the a carbon atoms do not bear hydrogen atoms. Heterocycles with a hydrogen atoms are stable up to about 70°C at this temperature the isomeric phosphetanes are formed. The syntheses of some sterically hindered phosphoranes require drastic conditions. 

It is comparatively easy to divide the N-substituents into bulky and nonbulky ones, but it is far more difficult to justify the decision in borderline cases and even more difficult to quantify the findings in a similar way to the Tolman cone angle, which gives a single value that can be calculated as the sum of the three contributing substituents on phosphorus. In short, the Tolman cone angle is valid for symmetrical and unsymmetrical (tertiary) phosphanes [113]. 

It is worth mentioning that Muller and Vogt have recently reintroduced the A, A concept for phosphinine ligands that have similar steric characteristics to NHC [119]. They call the two different angles the occupancy angles a and p, but the definitions are almost identical and they point out that the arithmetic average of a and p is very close to the Tolman cone angle 0 for tertiary phosphanes. 

When the labilities are reversed, that is when the NHC group is used as the anchor, ligand design again orientates itself on the successful hemilabile bidentate phosphanes. Now, we encounter pendant ether [34,35], tertiary amino [36,37], pyrido [11,38 0], imino [41-44] and carbonyl groups [30,45] in the sidechain. 

The ability of fluoro-2 -phosphanes to transform silyl ethers into fluorides was first observed during a study of the reactions of phosphorus pentafluoride and its derivatives R PF5 (n = 1, 2, 3 R = hydrocarbon group) with trimethylsilyl ethers. Subsequently, this reaction was proposed as a new method for the preparation of C-F compounds from silyl ethers or silicic acid esters with fluoro-A -phosphanes. Pentafluorophenyl-substituted fluoro-A -phos-phanes were found to react similarily, Other workers found that tctrafluoro(phenyl)-A -phos-phane. which was chosen as the most convenient reagent with regard to reactivity and stability, gave considerable amounts of elimination products, especially with primary and cyclic alcohols. Good yields of fluorinated products are obtained when stable carbocations can be formed at the site of substitution, such as in tertiary alcohols, but 2-phcnylethanol. benzyl alcohol and diphcnylmethanol, on the other hand, give only poor yields of fluorinated products ethers and polymers are the main products. ... 

Ammonio- and phosphoniohexafluorocyclobutanide ylides 11, prepared from pcrfluorocy-clobutene and tertiary amines or phosphanes, are soluble in a wide range of (even nonpolar) organic solvents and transfer fluoride, and therefore can be used as an easily soluble source of fluoride anions. Although they contain no ionic fluoride they react with fluoride anion acceptors such as silicon derivatives with elimination of thermodynamically favored fluoro-trimethylsilane to produce carbanions which can be quenched with suitable electrophiles. The reaction proceeds upon slightly heating the reactants in tetrahydrofuran or dimethylform-amide solution. 

Perfluoroalkenes react readily with tertiary phosphanes to form various products depending on the position of the multiple bond in the alkene. Internal alkenes (perfluorobut-2-ene and perfluorocyclobutene) undergo addition of phosphane at the multiple bond with subsequent... 

Reaction of the partially fluorinated aliphatic aromatic ketone 22 with bromotrifiuoromethane/ tris(diethylamino)phosphane leads to formation of the tertiary aryl alcohol 23. ° ... 

On the other hand, in the case of benzoyl fluoride, the reaction is very slow and does not lead to the ultimate formation of a tertiary alcohol, but of the product 24 of the esterification of benzoic acid by the tertiary alcohol.Benzoyl chlorides react with perfluoroalkyl iodides in the presence of tris(diethylamino)phosphane in a nonpolar solvent to give the corresponding polyfluoroalkyl aryl ketones 25 via substitution of the chlorine. 

On the other hand, tertiary phosphanes react with fiuorinated alkenes to form either vinyl-phosphoranes in the case of perfluorinated alk-l-enes, or ylides when perfluorinated alk-2-enes are used as starting materials. The latter lead to useful building blocks for Wittig-type reactions. 

The phosphaalkenes 14a and b react with tertiary phosphanes even at room temperature to provide the phosphorous ylide 15a-d. ... 

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