Phosphonium trimethyl

The reaction of higher alkyl chlorides with tin metal at 235°C is not practical because of the thermal decomposition which occurs before the products can be removed from the reaction zone. The reaction temperature necessary for the formation of dimethyl tin dichloride can be lowered considerably by the use of certain catalysts. Quaternary ammonium and phosphonium iodides allow the reaction to proceed in good yield at 150—160°C (109). An improvement in the process involves the use of amine—stannic chloride complexes or mixtures of stannic chloride and a quaternary ammonium or phosphonium compound (110). Use of these catalysts is claimed to yield dimethyl tin dichloride containing less than 0.1 wt % trimethyl tin chloride. Catalyzed direct reactions under pressure are used commercially to manufacture dimethyl tin dichloride. 

Trimethyl phosphite P(OMe)3 spontaneously iso-merizes to methyl dimethylphosphonate MePO-(OMe)2, whereas other trialkyl phosphites undergo the Michaelis-Arbusov reaction with alkyl halides via a phosphonium intermediate ... 

Small amounts of phosphonium complexone [1560] are sufficient to increase adhesion to the stratal rock. Table 18-4 illustrates an example for plugging solution with Portland cement and phosphonium complexone. Calcium chloride acts as a regulator of the setting time in the suggested composition. More precisely, phosphonium complexone stands for certain chelating phosphorous compounds (e.g., oxyethylidene diphosphonic acid, nitrilo-trimethyl phosphonic acid, sodium tripolyphosphate, or amiphol) [1540]. The mixture is applicable at low temperatures from 20° to 75° C. 

Figure 1.6 A. Trimethyl(phenyl)phosphonium chloride (a typical quaternary phos-phonium salt). B. Examples of quasiphosphonium salts.

LB films prepared from TCNQ octadecyl-dimethylsulfonium, octadecyl-methyl-ethyl-sulfonium, and octadecyl-trimethyl-phosphonium salts, transferred to substrates, and exposed to iodine vapor Absorption, infrared spectra, and ESR spectra Lateral d.c. conductivity was estimated (from energy of the maximum of the charge transfer absorption band) to be about 20-50 Scm-1 731, 732, 733... 

The results of the pulse radiolysis in aqueous solution of substituted phosphonium ions have been investigated38 in addition to those of the electrode reduction of benzyl triphenyl-phosphonium ion39 and quaternary phosphonium salts with hydrated electrons40-42. The radiolysis of methyltriphenylphosphonium, dimethyldiphosphonium and trimethyl-phenylphosphonium ions in neutral aqueous solutions leads to phosphoranyl radicals... 

The trimethylsilylated ylides (1), easily generated from trimethyl chlorosilane and ylides, react with aldehydes 2 to form vi-nylsilanes 3 (2,3). The vinylphosphonium silanolates 4 are also formed. Compounds 3 are versatile reagents for further reactions (4). The ylide J (with R1 =H) reacts with aldehydes 2 to give the dienes j). The oxidation of with the adduct 6, from triphenyl-phosphite and ozone, gives access to a generaT synthesis of acyl-silanes (trimethylsilylketones) (2). The silylated ylides react to form phosphonium salts 7 with halogen compounds. The salts 7.can be desilylated by fluorine ions. The disubstituted ylides JO Tormed can be converted in statu nascendi with aldehydes V[ into the tris-substituted olefin J2 (2,3). In the case of R3-I, vinyl... 

Citranaxanthene 543 is found in citrus fruits and is used as a food dye like P-carotene. The same phosphonium salt synthon 505 as used for the vitamin A synthesis is monoolefinated with the polyene dialdehyde 539. The Wittig reaction of the resulting 540 with phosphorane 541 followed by aldol condensation of the obtained 542 with acetone gives citranaxanthene 54 3 255,263) (Scheme 92). In the preparation of the polyenedial 539 l,4-dibromo-2-butene 544 is reacted with trimethyl... 

When activated by anionic catalysts [potassium fluoride, cesium fluoride, tctraalkylammonium fluorides, tris(dimethylamino)sulfonium difluorotrimethylsilicate, phosphazenium, hexa-methylpiperidinium and cobaltoccnium fluorides, tetrabuiylammonium difluoro(triphenyl-silyl)silicatc. the complex tetrakis(dimethylamino)ethene/pcrfluoropropene, ammonium (and phosphonium) periluorocyclobuianc ylides], trimethyl(perfluoroalkyl)silanes will generate C-Rp bonds from carbon-halogen bonds. 

Trimethyl(trifluoromcthyl)siIanc is easily fluorodesilylated by tris(dimethyIamino)suIfonium difluorotrimethylsilicate [TASF(Me)], tetrabutylammonium fluoride, or tris(diethylamino) (methylamino)phosphonium hydrogen difluoride and, if arenesiilfonyl fluorides are used to trap the trifluoromethyl anion, trifluoromethyl sulfones are formed in high yield. Trisfdiethyl-amino)(methylamino)phosphonium phenolate is also an effective catalyst for this reaction, but TASF(Me) is favored as it can achieve the quantitative transformation of ArSOjF into aryl trifluoromethyl sulfones. ... 

Another convenient one-pot and high-yielding procedure for the preparation of aryl tri-lluoromethyl sulfones 37 from readily available arenesulfonyl fluorides and trimethyl(trifluo-romcthyl)silanc or -stannanc, catalyzed by soluble nucleophilic agents such as tetrabutylam-monium fluoride, tris(diethylamino)(methylamino)phosphonium hydrogen difluoride, tris-(diethylamino)(methylamino)phosphonium phenolate, and tris(dimethylamino)sulfonium di-fluorotrimcthylsilicatc, has been reported. ... 

Phosphonium Tetrakis-[trimethyl-silyloxy]- (iodid) XIII/5, 170 [(R3SiO)3PO + R3Sil] El, 553 [(R3SiO)3PO + R3SiI]... 

N-acylaziridines occurs on treatment with triphenylphosphine with the formation of the ylides (67), thereby providing a route to a-substituted primary allylic amines via their in situ reactions with aldehydes.The reactions of triphenylphosphine with epoxides in phenolic media provide a new access to the vinyl-phosphonium salts (68). A route to 1-hydroxyalkylphosphonium salts is provided by the reactions of trimethyl- or triethyl-phosphine with aldehydes or ketones in the presence of anhydrous acids. The related 1-trimethylsiloxyalkylphosphonium salts can be isolated in the presence of trimethylsilyl chloride.Further Wittig-products have been isolated from the reaction of 1,2,3-indanetrione with triphenylphosphine, and, in related work, it has been shown that furoin is deoxygenated on heating with triphenylphosphine to form 2-furfuryl(2-furyl)ketone and triphenylphosphine oxide.The structure of the blue product from the reaction of triphenylphosphine with 2,3,5,6-tetracyano-7-oxabicyclo(2,2,1]hepta-2,5-diene has now been shown by X-ray techniques to be the stable ylide (69). ... 

Treatment of the phosphine resin 33 with alkyl bromides, e.g. 34, gave the corresponding phosphonium bromide 35 in excellent yields. The formation of the phosphorane was described as a cmdal step, for which the transport of the base to the phosphonium site within the polymer was essential. Various bases, such as sodium hydride, potassium tert-butoxide in THF, and n-butyllithium in dioxane, have been employed. Good results for the formation of the ylide were obtained with a mixture of sodium methoxide, methanol, and THF, and more recently with sodium bis(trimethyl)silylamide in THF [34, 35]. After the addition of aldehyde 36... 

---