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Triphenylphosphonium Bromide

Table 1. gem-Difluorocyclopropanes from Bromo(difluoromethyl)-triphenylphosphonium Bromide... [Pg.769]

The discovery of junipal focused the attention of Sorensen, who had been investigating the occurrence of polyacetylenes in Com-positae, on the possibility that these acetylenes were accompanied by thiophenes. From Coreopsis grandiflora Hogg ex sweet, 2-phenyl 5-(1-propynyl) thiophene (240) was isolated and its structure confirmed by synthesis of the tetrahydro compound, 2-phenyl-5-n-propyl-thiophene. From the root of tansy, the cis and trans isomers of methyl 5-(l-propynyl)-2-thienylacrylate (241) have been isolated. The total synthesis of trans (241) was achieved by reacting junipal with methylcarbethoxy triphenylphosphonium bromide (Wittig reaction) Several monosubstituted thiophenes, (242), (243), and... [Pg.117]

Triphenylmethylphosphonium bromide A pressure bottle is charged with a solution of 55 g (0.21 mole) of triphenylphosphine in 45 ml of dry benzene and cooled in an ice-salt bath. A commercially available ampoule of methyl bromide is cooled below 0° (ice-salt bath), opened, and 28 g (0.29 mole, approx. 16.2 ml) is added to the bottle in one portion. The pressure bottle is tightly stoppered, brought to room temperature, and allowed to stand for 2 days. After this time, the bottle is opened and the product is collected by suction filtration, the transfer being effected with hot benzene as needed. The yield of triphenylphosphonium bromide is about 74 g (99%), mp 232-233°. This material should be thoroughly dried (vacuum oven at 100°) before use in preparing the ylide. [Pg.105]

Carbohydroxy-n-butyl)triphenylphosphonium bromide Sodium methylsulfinylmethide... [Pg.1431]

Disubstituted-amino)triphenylphosphonium bromides (72) have been obtained from the reaction of triphenylphosphine dibromide and secondary amines in the presence of triethylamine. ... [Pg.17]

The reaction of //-a/w-y-bromocrotonaldehyde with triphenylphosphine in ether gave (3-formylallyl)triphenylphosphonium bromide (78) while y-bromo-j8-methylcrotonaldehyde gave the rearranged salt (79). [Pg.18]

A one-step synthesis of the triphenylphosphonium salt (81) from linalool or geraniol and triphenylphosphonium bromide, with simultaneous... [Pg.18]

The phosphonium salt (82) can be obtained by treatment of the vinyl alcohol (83) with triphenylphosphonium bromide." ... [Pg.19]

P 59] A third protocol differed from [P 57] and [P 58] by sequential insertion of all reactants instead of using a pre-mixed solution of nitrobenzyltriphenyl-phosphonium bromide and sodium methoxide. As above, flow was fed by electroosmotic means [13]. A 40 pi volume of a methanol solution of 0.01 M 2-nitrobenzyl-triphenylphosphonium bromide was filled into the first reservoir, 40 pi of a methanol solution of 0.015 M sodium methoxide in the second, 40 pi of a methanol solution... [Pg.533]

OS 78] [R 4a] [P 58] The Wittig reactions of five aldehydes with 2-nitrobenzyl-triphenylphosphonium bromide were investigated also at a 1 1 stoichiometric ratio [13]. Using optimized reaction conditions, improved yields were found for four of the five aldehydes. [Pg.535]

The ylide obtained from (methyl)triphenylphosphonium bromide reacts with morpholine derivatives 597 to give phosphonium salts 598 which upon treatment with -butyllithium are converted to new ylides 599. In a reaction with aldehydes, ylides 599 form iV-(l,3-disubstituted allyl)-morpholines 602 (Scheme 94) <1996AQ138>. Another less common nucleophile that can be used for substitution of the benzotriazolyl moiety in Af-(a-aminoalkyl)benzotriazoles is an adduct of iV-benzylthiazolium salt to an aldehyde which reacts with compounds 597 to produce adducts 600. Under the reaction conditions, refluxing in acetonitrile, salts 600 decompose to liberate aminoketones 601 <1996H(42)273>. [Pg.70]

After the final filtration the product is washed with two 100-ml. portions of ethyl acetate and two 100-ml. portions of anhydrous ether and dried for 24 hours at 80°. The dried, analytically pure vinyl triphenylphosphonium bromide, m.p. 186-190°, weighs 122-158 g. (66-86%). [Pg.66]

The present procedure is that described by the submitters.2 Vinyl triphenylphosphonium bromide has also been prepared by... [Pg.66]

VINYL TRIPHENYLPHOSPHONIUM BROMIDE (Phosphonium bromide, triphenylvinyl-)... [Pg.152]

Caution Because phenol and its solutions are corrosive, rubber gloves should be used in the following operations. The product, vinyl triphenylphosphonium bromide, has been found to induce a sneezing, allergic reaction and contact with it should be avoided. [Pg.152]

Reflux 6.9 g triphenylphosphine and 6.6 g lauryl bromide (or equimolar amount of homolog) in 40 ml xylene for 60 hours. Remove solvent and wash residue with 5X20 ml ether (by decanting) to get 11 g lauryl triphenylphosphonium bromide (I). To a stirred suspension of 5.6 g (0.011M)(I) in 50 ml ether add 0.01M butyllithium solution (see Organic Reactions 8,258(1954) for preparation). Stir Vz hour at room temperature and slowly add 1.66 g 3,5-dimethoxybenzaldehyde (preparation given elsewhere here) in 10 ml ether over Vi hour. After 15 hours, filter, wash filtrate with water and dry, evaporate in vacuum. Dilute residue with pentane, filter and remove solvent. Dissolve the residual oil in 25 ml ethyl acetate and hydrogenate over O.lg Adams catalyst at one atmosphere and room temperature for 2 hours. Filter and evaporate in vacuum to get the 5-alkylresorcinol dimethyl ether which can be reciystallized from pentane and demethylated as described elsewhere here. [Pg.44]

C H5)3P+—CHICOOC2HsI (1). The salt is prepared by iodination of a two-phase system of solid K2C03 and (ethoxycarbonylmethyl)triphenylphosphonium bromide in CH3OH m.p. 151°, 80% yield. [Pg.160]

Burns RJ, Smith RAJ, Murphy MP. Synthesis and characterization of thiobutyl-triphenylphosphonium bromide, a novel thiol reagent targeted to the mitochondrial matrix. Arch Biochem Biophys 1995 322 60-68. [Pg.337]

The other stereoselective synthesis/281 shown in Scheme 8, foresees conversion of Boc-L-Asp-OtBu 20 into the related (3-aldehyde 22 via the Weinreb amide 21 and its reduction with diisobutylaluminum hydride (DIBAL-H). Wittig condensation of 22 with the ylide derived from (3-carboxypropyl)triphenylphosphonium bromide using lithium hexamethyldisilaza-nide at —78 to 0°C, produces the unsaturated compound 23 which is catalytically hydrogenated to the protected L-a-aminosuberic acid derivative 24. Conversion of the co-carboxy group into the 9-fluorenylmethyl ester, followed by TFA treatment and reprotection of the M -amino group affords Boc-L-Asu(OFm)-OH (25). [Pg.228]

As shown in Scheme 1, isotretinoin (1) was first synthesized by Garbers et al. in 1968 utilizing a key Wittig condensation. Phosphonium salt 8 was prepared from direct treatment of vinyl p-ionol 7 with triphenylphosphonium bromide (PhsPaHBr) in ethanol. Subsequent addition of an excess of sodium ethoxide to 8 was followed by an ethanol solution of cij-3-formyl crotonic acid (9) to produce isotretinoin (1,2-cjs-vitamin A acid. [Pg.57]

Lund and Iversen first showed that azobenzene was an effective probase it is reduced to radical-anion at a low potential (—0.9 V vi. Ag/AgCl) and the reduced form is sufficiently basic to deprotonate benzylphosphonium salts. Its usefulness as an alternative to conventional bases was illustrated by the near quantitative production of stilbene by electrolysis of azobenzene in the presence of benzaldehyde and benzyl-triphenylphosphonium bromide (Table 2, entry 1). However, the concomitant formation of the carcinogenic benzidene, by acidic work-up of a product mixture which contains hydrazobenzene, is a severe drawback for this system. [Pg.139]


See other pages where Triphenylphosphonium Bromide is mentioned: [Pg.157]    [Pg.422]    [Pg.423]    [Pg.442]    [Pg.106]    [Pg.539]    [Pg.76]    [Pg.2424]    [Pg.2439]    [Pg.125]    [Pg.66]    [Pg.152]    [Pg.153]    [Pg.526]    [Pg.158]    [Pg.71]    [Pg.322]    [Pg.64]    [Pg.95]    [Pg.250]    [Pg.42]    [Pg.712]    [Pg.378]    [Pg.386]    [Pg.404]    [Pg.62]   


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Triphenylphosphonium

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