3- triphenylphosphonium

Bravo et al. studied the reaction of various ylides with monooximes of biacetyl and benzil. Dimethylsulfonium methylide and triphenylarsonium methylide gave 2-isoxazolin-5-ol and isoxazoles, with the former being the major product. Triphenylphosphonium methylide and dimethyloxosulfonium methylide gave open-chain products (Scheme 135) (70TL3223, 72G395). The cycloaddition of benzonitrile oxide to enolic compounds produced 5-ethers which could be cleaved or dehydrated (Scheme 136) (70CJC467, 72NKK1452). 

It has also been possible to prepare extremely stable triphenylphosphonium (trifluoromelhanesulfonyl)melhylide from chloromethyl tri fluoromethyl sulfone and triphenylphosphme [6 ] (equation 60)... 

Table 1. gem-Difluorocyclopropanes from Bromo(difluoromethyl)-triphenylphosphonium Bromide... 

Thus Ph3P=CH2 is triphenylphosphonium methylide (see pp. 274-304 of reference 2, or textbooks of organic chemistry for a fuller treatment of the Wittig reaction). 

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... 

Treatment of 8-[(4-cyanophenyl)methoxy]-7-formyl-2-cyclopentyl-2,3,4,6,11,1 la-hexahydro-l//-pyrazino[l,2-i]isoquinoline-l,4-dione with (Et0)2P(0)CH2C00Et and NaH in THF at 40 °C overnight, or with (2-pyridylmethyl)-, 4-[(ethoxycarbonyl)benzyl]-, (4-nitrobenzyl)-, and (meth-oxymethyl)triphenylphosphonium halogenide in the presence of KH in THF at room temperature gave 7-ethylene derivatives 386 (98MIP7). 

Phosphorus ylides like 1 can be prepared by various routes. The most common route is the reaction of triphenylphosphine 5 with an alkyl halide 6 to give a triphenylphosphonium salt 7, and treatment of that salt with a base to give the corresponding ylide 1 ... 

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. 

Carbohydroxy-n-butyl)triphenylphosphonium bromide Sodium methylsulfinylmethide... 

Meanwhile, it was found by Asai and colleagues [48] that tetraphenylphosphonium salts having such anions as Cl, Br , and Bp4 work as photoinitiators for radical polymerization. Based on the initiation effects of changing counteranions, they proposed that a one-electron transfer mechanism is reasonable in these initiation reactions. However, in the case of tetraphenylphosphonium tetrafluoroborate, it cannot be ruled out that direct homolysis of the p-phenyl bond gives the phenyl radical as the initiating species since BF4 is not an easily pho-tooxidizable anion [49]. Therefore, it was assumed that a similar photoexcitable moiety exists in both tetraphenyl phosphonium salts and triphenylphosphonium ylide, which can be written as the following resonance hybrid [17] (Scheme 21) ... 

If direct homolysis occurs in the case of tetraphenylphosphonium tetrafloroborate, triphenylphosphonium ylide was expected to function as a photoinitiator of radical polymerization because of its similar structure. Therefore, another milestone was reached by Kondo and colleagues [50] who investigated the use of triphenylphosphonium ethoxycarbonylmethylide (TPPY) (Scheme 22) as an effective photoinitiator for the polym-... 

Benzoxepin (4) was obtained in 55% yield by the reaction of phthalaldehyde with the bis-ylide generated from the bis(triphenylphosphonium) salt prepared from bis(bromomethyl) ether and triphenylphosphane.93,94... 

The thermolabile, unsubstituted 3-benzothiepin (3) can be synthesized by a double Wittig reaction, in analogy to the Knoevenagel condensation (vide supra). This is achieved by condensation of phthalaldehyde with the bis(triphenylphosphonium) salt of bis(bromomethyl) sulfide in the presence of lithium methoxide as base at — 30"C.68... 

This material may be converted directly to a phosphonium salt 1.40 g. (0.0054 mole) of the crude iodide is dissolved in 20 ml. of benzene, and 1.42 g, (0.0054 mole) of triphenylphosphine [Phosphine, triphenyl-] is added. On standing, 2.5 g. (77%) of the triphenylphosphonium salt precipitates as a colorless 1 1 complex with benzene, m.p. 135-137°. Recrystallization from methanol-benzene raises the melting point to 140-142°. Analysis calculated for C28H29PI CeH6 C, 68.23 H, 5.39. Found C, 68.15 H, 5.28. 

The present preparation illustrates a general and convenient method for the fnms-iodopropenylation of an alkyl halide.4 The iodopropenyl-ated material is not usually stable but is a useful synthetic intermediate. For example, it forms a stable crystalline triphenylphosphonium salt for use in the Wittig reaction, and under Kornblum reaction conditions (DMS0-NaHC03, 130°, 3 minutes) it gives an (E)-a,/9-unsaturated aldehyde.4 In addition to the phosphonium salt described in Note 15, the following have been prepared (4-p-methoxyphenyl-2-butenyl)-triphenylphosphonium iodide [Phosphonium, [4-(4-methoxyphenyl)-2-butenyl]triphenyl-, iodide], m.p. 123-127° (2-octenyl)triphenyl-phosphonium iodide [Phosphonium, 2-octenyltriphenyl-, iodide], m.p. 98° and (2-octadecenyl)triphenylphosphonium iodide [Phosphonium, 2-octadecenyltriphenyl-, iodide], m.p. 50°. 

Triphenylphosphonium cyclopentadienylide (12.109) reacts at the 2-position with diazonium ions and with diazocyclopentadiene (12.110), due to the aromatic character of the five-membered ring, as shown in the mesomeric structures 12.109 a and 12.109b (Ramirez and Levy, 1957, 1958a, 1958b). 

Alkyl-triphenylphosphonium-halogenide werden in 50%igem Alkohol an Quecksilber (geteilte Zelle) an der C-P-Bindung gespalten1 ... 

The resolution of racemic ethyl 2-chloropropionate with aliphatic and aromatic amines using Candida cylindracea lipase (CCL) [28] was one of the first examples that showed the possibilities of this kind of processes for the resolution of racemic esters or the preparation of chiral amides in benign conditions. Normally, in these enzymatic aminolysis reactions the enzyme is selective toward the (S)-isomer of the ester. Recently, the resolution ofthis ester has been carried out through a dynamic kinetic resolution (DKR) via aminolysis catalyzed by encapsulated CCL in the presence of triphenylphosphonium chloride immobilized on Merrifield resin (Scheme 7.13). This process has allowed the preparation of (S)-amides with high isolated yields and good enantiomeric excesses [29]. 

C22H32O3 15353-43-2) see Canthaxanthin (4-acetoxyretinyl)triphenylphosphonium chloride (04( 490102 15353-45-4) see Canthaxanthin 6-acetoxy-2,5,7,8-tctramethyl-2-(4-nitrophenoxymethyl>-4-chromanone... 

Triphenylphosphonium ylide reacts with the silylene complex 93 which has a highly electrophilic silicon center, to give the corresponding cationic adduct 94 [115]. The lengthening of the PC bond indicates a loss of the double bond character of the ylide and corresponds to the formation of a tetrahedral silicon center with four covalent bonds (Scheme 28). 

The first series of unsubstituted OPVs was synthesized by Drefahl and Horhold [102]. They started from 4-bromomethylbenzaldehyde and benzyltri-phenylphosphonium chlorides and successively produced the OPVs 77 with up to 8 phenylenevinylene units via repetitive in situ generation of the methylene-triphenylphosphonium functions. 

In addition to linear PPV oligomers, cyclic oligomers have been intensively investigated. Wennerstrom et al. described the synthesis of a cyclic cis,trans, cis,cis,trans,cis (Z,E,Z,Z,E,Z)-OPY hexamer (112) by a fourfold Wittig-type ole-fination, starting from two molecules of frfln5-stilbene-4,4 -dicarboxaldehyde and two molecules of l,4-xylylene-bis(triphenylphosphonium) dibromide [133]. 

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

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). 

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

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

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