Halides, alkyl, reaction with phosphines

These reactions may be considered to be a method of obtaining 1,3,2,5-dioxaborataphosphoniarinanes with different substituents at carbon and phosphorus atoms of the ring. Comparing the properties of cyclic oxyalkyl-phosphines and boryloxyalkylphosphines, it should be noted that in both cases the reaction with alkyl halides results in the formation of a tertiary phosphonium salt. The reaction with electrophilic reagents such as diphe-nylchlorophosphine and diphenylchloroborane proceeded quite differently [Eq. (100)]. 

An efficient resolntion of the racemic lithinm tert-bntylphosphine-borane complex 203 dnring deprotonation by n-BnLi/(—)-sparteine (11) and alkylation was reported by Liv-inghonse and Wolfe (eqnation 47) . One of the epimers 204/cp/-204 on warming to 0 °C crystallizes during a dynamic thermodynamic resolntion, and reaction with alkyl halides fnmishes the alkylation prodncts 205 with high ee values. Applying dihalides, essentially enantiomerically pure diphosphines snch as 206, besides few of the mcio-diastereomer, were obtained. Borane is removed by treatment with diethylamine to yield the free tertiary phosphines 207. 

Reactions with Alkyl Halides.— The in situ generation and reaction of chlorodi-phenylphosphine (2) with a-chloro-ethers gives good yields of a-alkoxyalkylphosphine oxides (20). The phosphine (2) is made from phosphorus trichloride and benzene, and the sequence looks like a very convenient one-pot procedure - the dangers of certain chloro-ethers aside ... 

Stelzer and co-workers reported a number of chiral water-soluble secondary phosphines [14], prepared by nucleophilic phosphination of primary phosphines with fluorinated aryl sulfonates in the superbasic medium DMSO/KOH. Further reaction with alkyl halides gives bidentate tertiary phosphines with P-chirality, but only racemic versions have been reported so far. Hanson et al. introduced so-called surface-active phosphines into asymmetric aqueous-phase catalysis. One of the main problems inherent to two-phase catalysis is the often very low miscibility of the substrates in the aqueous phase. Insertion of long alkyl chains between phosphorus atoms and phenyl groups in sulfonated phosphine ligands has been proven to increase reaction rates in the Rh-catalyzed hydroformylation of 1-octene [15], This concept was extended to a number of chiral ligands, i.e., the monoden-... 

The photolysis of a mixture of the alkene RCH=CH2 and (382) afforded (383) in good to high yields. The treatment of a large variety of a-thiomethyl- and a-selenomethyl phosphonates with BusSnH-AIBN results in their desulfurization or deselenation. The deselenation of phosphinoselenoic esters, e.g. (384), occurs imder attack by organometallic reagents, and ensuing reaction with alkyl halides provides phosphine oxides. ... 

Alkylphosphines (PR3) are analogs of the parent phosphine (PH3) in the same ways that alkylamines (NR3) are analogs of the parent ammonia (NHg). Phosphorus is directly beneath nitrogen in group 15 of the periodic table, so it is reasonable to expect that phosphines (PR3) should react similarly to amines (NR3). In most cases, this is a correct assumption, and phosphines react with alkyl halides by an mechanism in the same way as amines. In one example, benzyltriphenylphosphonium bromide (50) is formed by reaction of benzyl bromide with triphenylphosphine (49). This Sn2 reaction with phosphine and alkyl halides is sometimes called the Arbuzov reaction, named after Alexander Arbuzov (Russia 1877-1968). 

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) ... 

CLASSIFICATION OF REACTIONS BY TYPE OF COMPOUND SYNTHESIZED 16-47 Reaction of phosphines with Michael alkenes or with alkyl halides... 

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. 

A. Nucleophilic Reactions of the P=0 Group.—Tris(trifluoromethyl)-phosphine oxide (33) reacts with hexamethyldisiloxane to give a phos-phorane, whose n.m.r. spectrum at — 140 °C shows non-equivalent trifluoromethyl groups. Although this unusual reaction clearly involves nucleophilic attack of the phosphoryl oxygen on silicon at some stage of the reaction, a full study of the mechanism has not been published. Tertiary phosphine oxides can be converted cleanly into dichlorophos-phoranes (34) by treatment with two moles of phosphorus pentachloride. Alkylation of the sodium salt of tetraphenylmethylenediphosphine dioxide (35) with alkyl halides, in dimethyl sulphoxide, has been reported to... 

Phenols attached to insoluble supports can be etherified either by treatment with alkyl halides and a base (Williamson ether synthesis) or by treatment with primary or secondary aliphatic alcohols, a phosphine, and an oxidant (typically DEAD Mitsu-nobu reaction). The second methodology is generally preferred, because more alcohols than alkyl halides are commercially available, and because Mitsunobu etherifications proceed quickly at room temperature with high chemoselectivity, as illustrated by Entry 3 in Table 7.11. Thus, neither amines nor C,H-acidic compounds are usually alkylated under Mitsunobu conditions as efficiently as phenols. The reaction proceeds smoothly with both electron-rich and electron-poor phenols. Both primary and secondary aliphatic alcohols can be used to O-alkylate phenols, but variable results have been reported with 2-(Boc-amino)ethanols [146,147]. 

Many diorganogold(III) compounds with tertiary phosphines and arsines are now known. It has been shown previously (Section 1II,B) that the reactions of [AuRL] complexes with alkyl halides usually produced [AuXL] and a triorganogold(lll) species. In certain instances, however, the expected [AuXR2L] compounds were formed (46, 194, 195), notably in the reactions of [AuMeL] (L = PMe3, PMe2Ph, or AsPh3) with methyl iodide. 

Rh(CO)2 2(Por) complexes undergo addition reactions with carbonyl compounds and with alkyl halides to give acyl or alkyl Rhul(Por) similar to Rh1(CO)(phosphine)3 (Scheme 33).1.34... 

Other preparative methods of bis(trialkylsiIyl)phosphines involve reaction of RPLi2 with Me,SiCl (equation 8)28 and reaction of (Me3Si)2PLi with alkyl halides (equation 9)29. 

Primary and secondary phosphines may be readily alkylated with alkyl halides simply by nucleophilic displacement of halide by a phosphine anion (equation 50)84,392. With primary phosphines, dialkylation is readily achieved if excess base is used. Alkyl halides will also react with phosphine oxide and other phosphorous anions, especially if the reaction is performed under PTC392"395. 

Thiocarbonyl derivatives of 1,3-dioxolanes and 1,3-oxathiolanes are readily isomerized to the 2-carbonyl compounds as shown in Scheme 20. Alkylation of the sulfur atom with alkyl halides usually leads to ring-opened products (Scheme 21) (69JOC3011). Most of the other chemistry of the sulfur derivatives has focused on desulfurization and subsequent generation of alkenes. The reaction is shown in equation (20) and proceeds with cis elimination via carbene intermediate (see Section 4.30.2.2.5) and is usually carried out with a phosphine (73JA7161) or a zero-valent nickel complex (73TL2667). 

The Wittig reagent is prepared by the treatment of phosphonium salt with a strong base (such as PhLi, n-BuLi or lithium diisopropylamide). The phosphonium salts are prepared by the reaction of phosphines with alkyl halides. 

Diaminophosphoninm salts, [R2P(NR2)2] X, can be prepared by reactions of bis(dialkylamino)phosphines, RP(NR2)2, with alkyl halides. Diphosphines are cleaved by chloramine to form diaminophosphoninm salts (eqna-tion 7). ... 

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