Phosphonium bromides

Reactions involving ions can be favored to occur in the organic phase by use of phase-transfer catalysts. Thus the conversion of 1-chlorooctane to 1-cyanooctane with aqueous NaCN is vastly accelerated in the organic phase by 1.3 percent of tributyl (hexadecyl) phosphonium bromide in the aqueous phase. (Starks and Owens, J. Am. Chem. Soc., 95, 3613 [1973]). A large class of such promotions is known. 

Propargyl triphenyl phosphonium bromide [2091-46-5] M 381.4, m 179°. Recrystallises from 2-propanol as white plates. Also crystallises from EtOH, m 156-158°. IR has V 1440, 1110cm (P-C str). [Justus Liebigs Ann Chem 682 62 1965 J Org Chem 42 200 1977]. 

Carbohydroxy-n-butyl)triphenyl-phosphonium bromide Sulprostone... 

Bromo-j3-nitrostyrene and triphenylphosphine in dry benzene gave the phosphonium bromide (47). Using methanol as the solvent, the rearranged product (48) was formed, possibly via an azirine intermediate. Substituted -bromo-/3-nitrostyrenes yield the phosphoranes (49) and a phosphonium salt. When the aryl group is electron-donating, the reaction follows a different course to form the styrene (50) by initial attack of the phosphine on halogen. 

C. Miscellaneous.—Treatment of the phosphonium bromide (114) with one equivalent of butyl-lithium gave triphenylphosphine and benzylidene-methylamine via a Hofmann-like decomposition, whereas reaction with two equivalents of butyl-lithium resulted in the production of butyltriphenyl-phosphonium bromide. ... 

The iminophosphoranes (181) with imide bromides gave the amidino-phosphonium bromides (183) which, it appears from their temperature-variable n.m.r. spectra, are interesting fluxional molecules. The free energy of activation for the interconversion of (183a) and (183b) (R R = Pr R3 = Ph) is 17.2 0.9kcalmol-i. 

It is found that the tetra-isoamylphosphonium cation does not take a roughly spherical shape but accommodates an iodide ion 480 pm from the phosphorus atom. Neutron diffraction of phosphonium bromide crystals shows no evidence of hydrogen-bonding. The ructures of bis(trimethylphosphine)silicon tetrachloride and the iridium salt (134) are also reported. 

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... 

Reactions of Phosphonium Salts.- Interest continues in the effects of solvent on the rate of alkaline decomposition of phosphonium salts. It has now been shown that, in the respective reactions of hydroxide ion and methoxide ion with tetraphenyl-phosphonium bromide in mixtures of DMSO and methanol, the rates of the reactions increase as the proportion of the dipolar aprotic... 

Synthesis of the amino-triazole derivative (43) was performed in the authors laboratory by Pati et al. [52] (Scheme 7). Substituted benzyl bromide was reacted with triphenylphosphine to produce the phosphonium bromide starting material, 44. The Wittig reagent, obtained by treatment with sodium hydride, was reacted with 3,4,5-trimethoxybenzaldehyde 18 to generate the nitro-stilbene 45 in good yields. The alkyne 46 was obtained by bromination of the stilbene, followed by didehydrobromination. Compound 46 was then reacted under thermal conditions with benzyl azides... 

The synthesis of other biologically active thiazoles was described by Ohsumi et al. [50] and is shown in Scheme 16. Condensation of phosphonium bromide and 4-methoxy-3-nitrobenzaldehyde gave a 1 1 mixture of (Z)- and (-E)-stilbenes. ( )-stilbene 64 was purified by crystallization and then converted to bromohydrin 65 by NBS-H2O. Oxidation of the bromohydrin by DMSO-TFAA gave the bromoketone intermediate 66, which was condensed with thiocarbamoyl compounds in the presence of Na2C03 in DMF to give the corresponding 2-substituted thiazole derivatives (67a and b). Compound 67a... 

VINYL TRIPHENYLPHOSPHONIUM BROMIDE (Phosphonium bromide, triphenylvinyl-)... 

The white crystalline residue of crude phenoxyethyltriphenyl-phosphonium bromide (Note 4) is placed in a 3-1. two-necked flask equipped with a sealed stirrer and a reflux condenser fitted... 

Conversion of aromatic amines to azides was studied by Scechter et al. <2002TL8421> and these studies lead to the recognition of a new approach to tetrazolo[l,5- ]pyridine. Thus, reaction of 2-aminopyridine 142 with butyl-lithium followed by treatment with azidotris(diethylamino)phosphonium bromide gave rise to tetrazolo[l,5- ]pyr-idine 1 in 80% yield. The first intermediate is obviously the azide 7. 

The optical purity of the phosphonate (123)148 and the absolute configuration of the phosphonium bromide (124)149 have been established. Optical rotatory dispersion and circular dichroism have been used in stereochemical studies of phospholipids150 and adenosine-5 -triphosphate.151... 

X-Ray.—The crystal and molecular structure of tri-o-tolylphosphine, its oxide, sulphide, and selenide (125) have been compared. The mean P—C bond lengths appear to be determined by the n-electron density along the P—C bond and intramolecular steric interactions, d-Orbital participation was considered to be of little importance.152 X-Ray diffraction established the structure of diphosphinofumarate (126)153 and showed that the phospholanium iodide (127) has an envelope ring with the methyl group at the point of the flap.154 The bicyclic phosphonium bromide (128) has a distorted half-chair phosphorus-containing ring, one of the P—C bonds in the... 

PH4Br PHOSPHONIUM BROMIDE 79.2715 -4.0989E+03 -2.8848E+01 3.2807E-02... 

Transformation of [4- F]fluorobenzaldehydes into [4- F]fluorophenyl-alkenes using the Wittig reaction has been relatively unexplored. Examples are shown in Scheme 35. It requires the in situ generation of the ylid [171] by reaction of the phosphonium bromide with propylenoxide [172]. These conditions, successfully used in carbon-11 chemistry [173], have however the drawback of leading to a mixture of Z and E stereoisomers. 

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