Tributylphosphine oxide

BU3P. A rapid redox reaction takes place to yield the active Pd(0) species and tributylphosphine oxide. The Pd(0) thus generated is a phosphine-free cata-lyst[341]. Severe reaction conditions are necessary, or no reaction takes place, when Pd2(dba)3 is used in the elimination reaction of cyclic allylic compounds with an excess of -Bu3P[342]. 

The amount of molecular sieves 4 A largely influences the product s ee[11]. Usually 100 mg (for the CMHP oxidation) or 1 g (for the TBHP oxidation) of MS 4A for 1 mmol of substrate is enough however, in the case where chemical yield and/or optical yield are not high, use of excess MS 4A often improves them. The addition of achiral ligands such as tributylphosphine oxide, tri-o-tolyl- and tri-/)-tolylphosphine oxides, hexamethylphosphoric triamide, triphenylpho-sphate, lutidine N-oxide, and l,3-dimethyl-2-imidazolidinone were found to be less effective than that of triphenylphosphine oxide in the epoxidation of chalcone. 

This method has been used only a few times, despite the high yields reported. In the procedure, the hemiacetal was activated with tributylphosphine oxide (4.5 equiv) and triflic anhydride (2.1 equiv) for 2 h at 0 °C, followed by an addition of the giycosyi acceptor. As a result, the isopropyl riboside 46 was prepared in 93% and the cho-lestanyl riboside 47 was prepared in 75%, both with a-anomeric selectivity. 

The reaction using 11a as a substrate in the presence of several oxides as additives revealed that addition of tributylphosphine oxide, hexamethylphos-phoric triamide, and dimethyl sulfoxide all accelerate the reaction considerably. Furthermore, when about 10 molar amounts of N-methylmorpholine M-oxide (NMO) is added to the alkyne-cobalt complex 12b in THF,the reaction proceeds even at room temperature and cyclopentenone 13 b is obtained in 37% yield accompanied by another rearranged product, the methylenecyclobutanone 35, obtained in 23% yield as a mixture of ( )-and (Z)-isomers (Scheme 14). These facts indicate that dissociation of the carbonyl ligand of the alkyne-cobalt complex 12 is the rate-determining step in this rearrangement. This is also supported by the fact that under a CO atmosphere in refluxing THF the reaction is completely suppressed. 

The gas chromatography of complexes with mixed ligands (e.g. 1,1,1,2,2,6,6,7,7,7-decafluoro-heptane-3,5-dione with neutral donors such as dibutylsulfoxide, TBP and tributylphosphine oxide) has been extensively studied but the results leave much to be desired with respect to their use in analytical separations. 

Note TBPO, tributylphosphine oxide. TOPO, trioctylphosphine oxide. TPPO, triphenylphosphine oxide, acac, acetyl acetone. HDEHP, di(2-ethylhexyl)phosphoric acid. MIBK, methylisobutyl ketone. DMDOHEMA, N,iV-diniethyl-iV,iV-dioctylhexylethoxymalonamide. 

The triorganotin chloride adducts readily exchange with base or with other adducts. The diorganotin dichlorides form only 1 1 adducts with tributylphosphine, even at high base to acid ratios. The lower dialkyltin dichlorides prefer to form 1 1 adducts (at 1 1 mole ratios) with tributylphosphine rather than tributylphosphine oxide (TBPO), whereas... 

The reaction of thiophenes and benzo[3]thiophenes with alkylidenecyclopropanes in the presence of catalytic amounts of Pd(PPh3>4 and tributylphosphine oxide has been reported (Scheme 14) <2002JOC3445>. Yields are around 60%. The role of tributylphosphine oxide in the detailed mechanism is not clear, but it certainly served to accelerate the addition reaction. 

Like tertiary amines, tertiary phosphines are readily transformed into the corresponding oxides, phosphine oxides. Tributylphosphine in di-chloromethane is oxidized with ozone adsorbed on silica gel at -70 "C to tributylphosphine oxide in 92% yield [113]. Other oxidants used to transform phosphines into phosphine oxides are potassium peroxysulfate [205], argentic oxide [381 ], manganese dioxide [813], and barium manganate [S55] (equation 537). 

Mukaiyama reported an alternative method for the generation of oxophosphonium type intermediates using the reaction of tributylphosphine oxide and triflic anhydride, and applied this reaction to the synthesis of ribofuranosides [415]. 

There are very few examples of Lewis base-promoted allylations of aldehydes with allylstannanes. In 1992 Baba disclosed an intriguing method for allylation of aldehydes with allyl- and 2-butenyltributylstannanes in the presence of catalytic-amounts of dibutyltin dichloride and certain coactivators such as tetrabutylammo-nium iodide, tributylphosphine oxide, HMPA or tetraphenylphosphonium iodide [76]. No definitive mechanistic information is available on the role of the co-activators the authors speculate that the ligands accelerate the metathesis to form allyldibutyltin chloride which is the actual nucleophile. The same group has recently reported the use of a lead(II) iodide/HMPA catalyst for the allylation of a,yff-epoxyketones [76bj. 

Ring-opening reactions to yield aldehydes or ketones were reviewed [7-10]. Isomerization may be thermally induced [7] or may occur in the presence of basic or acidic agents [11]. Lithium bromide associated with tributylphosphine oxide or hexamethylphosphoric triamide (HMPA) has been used [12,13], but transition metal complexes may be more attractive [14-21]. In this work the performances of catalytic systems, e.g. "LiBr/HMPA/toluene", "Co2(CO) /MeOH", "NiBr2(PPh3)2/ Zn/PPh3/THF", etc. are compared for the isomerization of 3a and of analogues. Supported catalysts have also been studied. 

Species identified by ESR spectroscopy indicate that tertiary butoxy radicals react with phosphines to give products which undergo a scission (13.186). In the case of -butylphosphine, however, t-butyl dibutylphosphinite and tributylphosphine oxide are formed, indicating that both a and P scission have taken place (13.187). 

In Table I we present some information on idealized frameworks, determined from the data on the known structures of gas, peralkylonium salts and tributylphosphine oxide hydrates. The hydrate number can be determined using the data of this Table and taking into account the nature of the guests concerned by Jeffrey s formula [3 ]... 

TABLE II. Some properties of tetraalkylonium salts and tributylphosphine oxide polyhydrates, whose phase diagrams have been studied ... 

Scheme 74) (2002JCS(P1)599). Dimerization of 232 in several polar solvents resulted in the previously reported [2 -f 4] dimer 233, whereas dimerization in DMSO as solvent in the presence of tributylphosphine oxide, or pyridine instead unexpectedly, occurs across the C=0 bond of the ketene function, giving raise to dioxinone 234 (1992JOC7078). 

In an attempt to improve on the original PKR, Pauson reported on the effects of various additives. Phosphines, ether as preformed cobalt species or simply added to the PKR, only served to reduce the rate and yield of the reaction. On the other hand, ultrasound and tributylphosphine oxide proved equally effective at accelerating the rate of reaction and increasing the overall yield of the PKR. The reaction yields were described as erratic varying irreproducibly as the reaction atmosphere was changed. The use trimethylamine-A-oxide was mentioned but no results were reported. 

For purified tributyloctadecylphosphonium-modified montmorillonite (3C4CigPBr-MMT), tributylphosphine, alkenes, tributylphosphine oxide, and alkanes were detected, indicating the suggested occurrence of Sn(P) and p-elimination mechanisms [27, 43], Even though it was not possible to identify with certainty the mechanism involved in the thermal decomposition of 3C4Ci6PBr-MMT, it is highly probable that it proceeded via a different pathway than pure surfactant, because the measured degradation temperature was lower than that for the pure surfactant. 

The bifunctional catalyst 9 was then applied in a total synthesis of Epo-thilone A and B in 2000 by the Shibasaki group (Scheme 19.6). The key step is the enantioselective cyanosilylation to a thiazole-based a,p-unsaturated aldehyde. In the presence of catalyst 9 (5 mol%) and tributylphosphine oxide (80 mol%) in dichloromethane, the corresponding cyanohydrin was obtained in 97% yield and 99% enantiomeric excess. It should be noted that slow addition of trimethylsilyl cyanide (>50 h) was essential to aehieve this result. 

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