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Phosphines from alkyl halides

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... [Pg.144]

Ethylene oxide or 1,2-epoxybutane may also be used for the synthesis of ylides. The resulting ylide is in equilibrium with its conjugated salt (equation 15). The use of ethylene oxide offers some advantages over more conventional bases used in Wittig reactions. The application is simple since ylides and most often also phosphonium salts (from phosphine and alkyl halide) need not to be prepared separately. The reaction medium is neutral, so that base-induced side reactions fail to appear. The method is however less applicable to weakly acid phosphonium salts, since deprotonation requires high temperatures (150 C). [Pg.175]

Unsymmetrical ligands, e.g., Ph2PCH2PH2 (25), can be prepared from chloromethyl-diphenyl-phosphine, phosphine, and potassium hydroxide in a two-phase system (toluene/water) using nBu4NCl as a phase-transfer catalyst.35 This general procedure can be extended to the synthesis of the primary phosphine (26) by selective alkylation of phosphine with alkyl halides in the presence of concentrated aqueous potassium hydroxide in DMSO, or in a two-phase system involving a phase-transfer catalyst.36... [Pg.258]

Pertinent to this review is the study by Henderson and Buckler (130) on the kinetics of the reactions of variously substituted phosphines with alkyl halides. These authors point out that while attack by phosphine on an alkyl halide is almost certainly SN2, it does not follow that reaction proceeds by attack from the rear with inversion. For nucleophiles capable of expanding their valence shells, including esters of phosphorous... [Pg.74]

Trimethylsilyl esters of both functionalized and non-functionalized phosphinic acids, R2P(0)0SiMc3, have been prepared from the respective alkyl halides and bis(trimethylsi-lyl) alkylphosphonites, RP(OSiMe3)2, (Michaelis-Arbuzov alkylation) as part of a novel sequence in which the latter are obtained in situ from alkyl halides and bis(trimethylsilyl) hypoghosphite [HP(OSiMe3)2] in the presence of Et3N (Michaelis-Becker-like alkyla-... [Pg.72]

The trialkyl compounds, AlkgArPX, are obtained from dialkylaryl-phosphines and alkyl halides ... [Pg.60]

The well-known approach to functionalized phosphorus ylides based on the three-component reactions of triphenylphosphine (TPP), dialkyl acet-ylenedicarboxylates (DAAD) and various EH-nucleophiles (E = N, O, S, C) stabilizing by protonation a reactive intermediate generated from the reaction of TPP and DAAD followed by addition of a conjugated base to the vinyltriphenylphosphonium salt formed, has continued to find application. When 2-bromoacetamide was used as a nucleophile in this reaction, a-amido phosphorus ylides (52) were formed, even despite the high reactivity of P(III) atom of phosphines towards alkyl halides and a-halocarbonyl compounds. Ethyl phenylcarbamate reacted in a similar way ((52), Y = OEt). The other series of stable a-amido phosphorus ylides (53) was produced from the above reaction with l-benzylidene-2-phenylhydrazines. The reaction of TPP,... [Pg.90]

In the Wittig reaction an aldehyde or ketone is treated with a phosphorus ylid (also called a phosphorane) to give an alkene. Phosphorus ylids are usually prepared by treatment of a phosphonium salt with a base, and phosphonium salts are usually prepared from the phosphine and an alkyl halide (10-44) ... [Pg.1231]

It is possible to replace one isocyanide by triphenylphosphine, or to replace two isocyanides with diphos, giving phosphine analogues of these complexes. These species are not available from analogous reactions of phosphine-palladium(O) and (II) complexes. Reactions with active alkyl halides proceeds with oxidation nitric oxide also oxidizes these complexes. [Eqs. (31, 32)]. [Pg.75]

Wittig reactions are versatile and useful for preparing alkenes, under mild conditions, where the position of the double bond is known unambiguously. The reaction involves the facile formation of a phosphonium salt from an alkyl halide and a phosphine. In the presence of base this loses HX to form an ylide (Scheme 1.15). This highly polar ylide reacts with a carbonyl compound to give an alkene and a stoichiometric amount of a phosphine oxide, usually triphenylphosphine oxide. [Pg.28]

B. By Hydrolysis Reactions.—Details have appeared of the synthesis of dibenzophosphorin oxides (15) from 5-alkyldibenzophospholes, by reaction with methyl propiolate in the presence of water, and of confirmatory syntheses from phosphinic acid chlorides, as shown below. Evidence for the suggested mechanism of the ring-expansion reaction is presented. The hydrolysis of enamine phosphine oxides is an efficient, although somewhat indirect, method for the preparation of j8-ketoalkylphosphine oxides (16) [see Section 3(iii), for the preparation of enamine oxides]. Reasonable yields (48—66%) of trialkylphosphine oxides (17) have been obtained by the alkaline hydrolysis of the products from the pyrolysis at 220 °C of red phosphorus with alkyl halides, in the presence of iodine. [Pg.57]

This is an extremely useful reaction for the synthesis of alkenes. It involves the addition of a phosphonium ylid, e.g. (136), also known as a phosphorane, to the carbonyl group of an aldehyde or ketone the ylid is indeed a carbanion having an adjacent hetero atom. Such species are generated by the reaction of an alkyl halide, RR CHX (137), on a trialkyl- or triaryl-phosphine (138)—very often Ph3P—to yield a phosphonium salt (139), followed by abstraction of a proton from it by a very strong base, e.g. PhLi ... [Pg.233]

Biaryl synthesis from aryl halides is a more interesting reaction due to the value of these molecules and their difficult access by chemical methods. The first electrosyntheses were simultaneously done in 1979-80 by three groups [21-23] who used NiCljPPha (1-20%) as catalyst precursor in the presence of excess PPhs. Later, several groups investigated the use of bidentate phosphines like dppe associated with nickel in the synthesis of various biaryls, and notably 2,2 -bipyridine and of 2,2 -biquinoline from respectively 2-chloropyridine and 2-chloroquinoline [24], More recently new nickel complexes with l,2-bis(di-2-alkyl-phosphino)benzene have been studied from both fundamental and synthetic points of view [25]. They have been applied to the coupling of aryl halides. [Pg.145]

Preparation of alkenes Ketone reacts with phosphorus ylide to give alkene. By dividing a target molecule at the double bond, one can decide which of the two components should best come from the carbonyl, and which from the ylide. In general, the ylide should come from an unhindered alkyl halide since triphenyl phosphine is bulky. [Pg.216]

Peptidomimetics in which one amide bond is replaced by a phosphinic acid (R-P(0H)(=0)-R phosphinic peptides ) are of interest as potential protease inhibitors [17-19]. These compounds have been prepared either from orthogonally protected phosphorus-containing monomers [17,18,20], or by forming the phosphorus-containing fragments on solid phase, as sketched in Figure 11.4 [19,21], Phosphinic acids have been prepared on solid phase mainly by reaction of carbon electrophiles with monoalkylphosphinates. As carbon electrophiles, acrylates, aldehydes, reactive alkyl halides, or a, 3-unsaturated ketones can be used. [Pg.315]


See other pages where Phosphines from alkyl halides is mentioned: [Pg.275]    [Pg.5]    [Pg.84]    [Pg.307]    [Pg.22]    [Pg.719]    [Pg.306]    [Pg.157]    [Pg.595]    [Pg.8]    [Pg.160]    [Pg.25]    [Pg.383]    [Pg.502]    [Pg.533]    [Pg.103]    [Pg.36]    [Pg.25]    [Pg.65]    [Pg.129]    [Pg.69]    [Pg.70]    [Pg.162]    [Pg.386]    [Pg.388]   
See also in sourсe #XX -- [ Pg.1685 ]




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From alkyl halides

Phosphine alkylation

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