Lithium-Diphenyl

Two reports of the hitherto little documented attack of organophosphide anions on halogen have appeared. Addition of 1,2-dibromoalkenes to lithium diphenyl-phosphide in THF gives an acetylene and tetraphenyldiphosphine81 (Scheme 1). 

As stated above, intermolecular coupling reactions between carbon atoms are of limited use. In the classical Wurtz reaction two identical primary alkyl iodide molecules are reduced by sodium. n-Hectane (C100H202), for example, has been made by this method in 60% yield (G. Stallberg, 1956). The unsymmetrical coupling of two alkyl halides can be achieved via dialkylcuprates. The first halide, which may have a branched carbon chain, is lithiated and allowed to react with copper(I) salts. The resulting dialkylcuprate can then be coupled with alkyl or aryl iodides or bromides. Although the reaction probably involves radicals it is quite stereoselective and leads to inversion of chiral halides. For example, lithium diphenyl-cuprate reacts with (R)-2-bromobutane with 90% stereoselectivity to form (S)-2-phenylbutane (G.M. Whitesides, 1969). 

Lithium dialkynylcuprates behave similarly with alkynyliodonium tosylates and lead to conjugated diynes (equation 133)109. Unsymmetrical diynes can be prepared with moderate selectivity by this method, although they are accompanied by symmetrical diynes derived from the alkynyliodonium component. The treatment of lithium diphenyl- and dialkylcuprates with alkynyliodonium tosylates has also been investigated and affords alkyl- and phenyl-substituted alkynes (equation 134)109. 

The synthetic power of these silylcuprate and stannylcuprate reactions lies in the synthetic utility of the product silanes and stannanes for carbon-carbon bond formation and also in the utilization of the silyl [38] or stannyl substituents as agents for stereocontrol and regiocontrol. Additionally use of appropriate silylcuprates permits conversion of the produced C Si bond into a C OH bond (Tab. 3.1) [39]. This C Si to C OH conversion is a particularly difficult transformation for an allyl silane and the development of lithium diphenyl(2-methyl-2-butenyl)silylcuprate for this purpose illustrates the characteristic transformations of silylcuprates (Scheme 3.1) [14e]. Several silyl substituents convertible into hydrosy groups are not amenable to the cuprate methodologj vinyl silanes - generated by... 

Sequential treatment of the bromopenem (100) with lithium diphenyl-... 

Several reports have appeared of the application of unusual organometallic reagents in phosphine synthesis. Treatment of 2-lithiopyridine with anhydrous zinc chloride results in the formation of a 2-pyridylzinc reagent which can be used to introduce the 2-pyridyl group at phosphorus in a controlled manner. Thus, e.g., in its reaction with phenyldichlorophosphine, the 2-pyridyl-(phenyl)chlorophosphine (15) is formed. This has then been converted via the phosphide route into a new class of binucleating ligands (16). The sterically crowded dichlorophosphine (17) (accessible from the reaction of phosphorus trichloride with lithium diphenyl(2-pyridyl)methanide) is converted into the thermally stable phosphirane (18) on treatment with calcium, strontium or barium cyclooctatetraenide.The reaction of phenyldichlorophosphine with the readily accessible titanacycle (19) affords a convenient route to the phosphetene (20). ... 

Estrone, a key intermediate in the preparation of medicinally useful 19-norsteroids, can now be prepared in high yield at the remarkably low temperature of 35° from A -androstadiene-3,17-dione 17-ethyleneketal (1) by reaction with lithium-diphenyl in THF in the presence of a suitably acidic hydrocarbon such as diphenyl-methane to intercept the by-product methyllithium and prevent its addition to the potential 17-carbonyl group. ... 

Ethers Aiuminum bromide. Aluminum chloride. Boron tribromide. Boron trichloride. Diborane. Diphenyl phosphide, lithium salt. Hydrobromic acid. Hydriodic acid. Lithium bromide. Lithium bromide-BFt etherate. Lithium diphenyl. Methylmagnesium iodide. Pyridine hydrochloride. Sodium iodide. Sodium-Potassium alloy. Triphenylphosphine dibromide. 

Full details of the demethylation of the pentacyclic diether (57) with lithium diphenyl phosphide have been published. Selective cleavage of the methoxy-group is achieved even when a four-fold excess of phosphide is present. 

Reducing agents Aluminum hydride. Bis-3-methyl-2-butylborane. n-Butyllithium-Pyridine. Calcium borohydride. Chloroiridic acid. Chromous acetate. Chromous chloride. Chromous sulfate. Copper chromite. Diborane. Diborane-Boron trifluoride. Diborane-Sodium borohydride. Diethyl phosphonate. Diimide. Diisobutylaluminum hydride. Dimethyl sulfide. Hexamethylphosphorous triamide. Iridium tetrachloride. Lead. Lithium alkyla-mines. Lithium aluminum hydride. Lithium aluminum hydride-Aluminum chloride. Lithium-Ammonia. Lithium diisobutylmethylaluminum hydride. Lithium-Diphenyl. Lithium ethylenediamine. Lithium-Hexamethylphosphoric triamide. Lithium hydride. Lithium triethoxyaluminum hydride. Lithium tri-/-butoxyaluminum hydride. Nickel-aluminum alloy. Pyridine-n-Butyllithium. Sodium amalgam. Sodium-Ammonia. Sodium borohydride. Sodium borohydride-BFs, see DDQ. Sodium dihydrobis-(2-methoxyethoxy) aluminate. Sodium hydrosulflte. Sodium telluride. Stannous chloride. Tin-HBr. Tri-n-butyltin hydride. Trimethyl phosphite, see Dinitrogen tetroxide. 

Lithiophosphide reagents have also found application in the synthesis of a range of chiral phosphines based on carbohydrate systems, e.g., (43), the key step being nucleophilic ring-opening of epoxide derivatives with lithium diphenyl-phosphide. A lithiophosphide-tosylate route has been used in the synthesis of the carbohydrate-based diphosphine (44). Conjugate addition of lithium diphenyl-phosphide to a,P-unsaturated carboxylic esters is the key step in the synthesis of... 

Lithium dimethyl cuprate, 209-215 Lithium diphenylarsenide, 341 Lithium diphenyl cuprate, 234 Lithium diphenylphosphide, 340-341, 645 Lithium diphenylphosphinate, 340 Lithium di-n-propyl cuprate, 245 Lithium ethynyltrialkylborates, 324-325 Lithium fluoride, 17... 

DEHALOGENATION Lithium diphenyl-phosphide. Potassium t-butoxidc. Sodium iodlde-Copper. DEHYDRATION Ferric chloiide-Silica gel. Phenylene orthosulfite. DEHYDROBROMINATION Hexamethyl-phosphoric triamide. Lithium diiso-propylamide. Potassium f-butoxide. DEHYDROCYAN ATION Sodium naphthalenide. 

Distribution of functional groups in polymer-supported reagents wd catalysts has been studied with a scanning electron microprobe. Chloromethylation of 2% cross-linked 300-600 nm polystyrene beads with chloromethyl methyl ether and stannic chloride to 0.67 mequiv Cl/g (2S) followed by phosphination with lithium diphenyl-... 

In THE solution, lithium diphenyl phosphide exists as [Li(THF)4]+[PPh2], whereas in Et20 solution it is dimeric [64], and in the solid state probably polymeric as (8.46c). In [Li(12-crown-4)]+[PPh2] the Li+ cation is completely enclosed by the crown ether, allowing a free phosphide anion to exist in the crystal structure (8.46d). A similar discrete phosphide anion is found in the pyridyl phosphide (8.46e) and in (8.46g). Lithium forms covalent-type complexes with imido analogues of P oxo-anions (Chapter 7.4). 

Phosphide anions are excellent nucleophiles and are very reactive to alkylating agents and metal-lophosphine derivatives are of importance as phosphide transfer agents. Lithium diphenyl phosphine can be used to prepare water-soluble phosphines. Dilithium phenyl phosphine can be used in the synthesis of phosphiranes, phosphetanes and so forth (Chapter 6). Lithium bis(trimethylsilyl)phos-phanide, LiP(SiMe3)2, is useful for the synthesis of compounds with P-Si linkages (Figure 9.11). 

The phosphorous derivative 16 was prepared by reaction of lithium diphenyl phosphide with PEG bromide, and the related derivative 18 was prepared by reaction of PEG itself with dichlorophenyl phosphine. Derivatives 16 and 1 were used to prepare the polymer-bound rhodium compounds 17 and 1, respectively. These rhodium complexes were of interest as water-soluble, recoverable catalysts. Whitesides and coworkers have prepared a rhodium derivative similar to 17 using PEG with molecular weight of approximately 1000 g/mol. We found the products derived from such low molecular weight PEG s to be amorphous and less readily recoverable (by precipitation) in comparison to our higher molecular weight (6800 g/mol) derivatives. Catalytic studies of 17 and are in progress. 

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