Phosphine Reagents

The second reaction uhhzed with this reagent was the Mitsunobu reaction ]97], a reachon known to require chromatographic purification to obtain pure product because side-products are formed. An insoluble polymer approach to this problem is known [98], however, the nature of the support means that the reachon is inherently heterogeneous (see above). The reaction between phenol and a series of alco- 

In a continuation of their initial study, Janda and Wentworth disclosed an optimized version of the polyethylene glycol-supported triarylphosphine reagent (20) 

Hypervalent iodine reagents have become extremely valuable tools in organic chemistry [121]. Reagents such as the Dess-Martin periodinane have received immense attention because of its efficiency and mild reaction conditions. The precursor to the Dess-Martin periodinane, o-iodoxybenzoic acid (IBX) has also be- 

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This procedure also incorporates the use of bis(3-dimethylamino-propyl)phenylphosphine as a combined amine-phosphine reagent. The merits of using this basic phosphine as opposed to a tertiary amine and a phosphine lies in the ease of workup. Excess phosphine and phosphine sulfide can be removed by extraction with aqueous dilute acid. 

Se = -174). Diselenasilirane 59 was found to be another useful precursor of silaneselone 57 when treated with an equimolar amount of a phosphine reagent... 

To label cell-surface azide-glycans, the cells are reacted for 1 hour using a final concentration of 1 mM biotin-PEG-phosphine reagent dissolved in PBS, pH 7.4. 

Figure 17.20 An azido-palmitic acid derivative can be added to cells to obtain palmitoylated proteins that contain an azide group able to participate in the Staudinger ligation reaction. Biotinylation of these post-translationally modified sites then can be done in vivo using a biotin-phosphine reagent.

Relies, H.M. and Schulenz, R.W., Chemical transformations with regenerable polymer-supported trisubstituted phosphine dichlorides. The efficacious incorporation of phosphine reagents on polymer supports, /. Am. Chem. Soc., 96, 6469, 1974. 

In one family of experiments, a pair of phosphine reagents was used to evaluate the relative reactivities of PyO towards the peroxo intermediate. The reactivity ratio proved to be independent of the PyO used, consistent with the absence of the Py group in the intermediate. The most reactive phosphines were those with electron-donating substituents (57). 

Tokitoh and co-workers further succeeded in the synthesis of overcrowded diarylstannylenes, Tbt(Tcp)Sn (170 Tcp = 2,4,6-tricyclohexylphenyl) and Tbt (Tpp)Sn [171 Tpp = 2, 4,6-tris(l-ethylpropyl)phenyl], by the exhaustive desulfurization of the corresponding tetrathiastannolanes with a trivalent phosphine reagent (Scheme 14.74). Since only a few convenient precursors have been available for the generation of stannylenes, this new method should provide us with a useful synthetic route for a variety of overcrowded stannylenes. The successful synthesis of a series of Tbt-substituted diarylstannylenes enabled the systematic comparison of their electronic absorptions with those of the previously reported overcrowded diarylstannylenes, which led to the elucidation of the substituent effect on the n—transition of stannylenes. 

High-yield syntheses of Os3Pt clusters are available using this rationale. Thus treatment of Os3(/i-H)2(CO)10, which contains a formal Os=Os double bond, with Pt(C2H4)2(PR3) affords the tetrahedral 58-electron cluster Os3Pt(/i-H)2(CO)10(PR3) (1) (40,40a), whereas with the bis-phosphine reagent... 

In addition to the organo-phosphate and -phosphinate reagents, a variety of other potentially anionic ligands has been proposed as extractants for U0224 Most notable among these are the... 

Recent developments in this area include the use of poly[hydroxy(tosyloxy)-iodo]styrenes [80], chiral 2-(a-alkoxyalkyl) analogs of [hydroxy(tosyloxy)-iodo]benzene [81 - 83], and iodine(III)-phosphonate and -phosphinate reagents [84] for C-oxygen bond formation at a-carbon. Oxysulfonylations at the a-carbon atoms of carboxylic anhydrides with [hydroxy(sulfonyloxy)iodo]arenes have also been documented [85]. 

CyclizMion of unsaturated ethers.2 Reaction of y- or 6-unsaturated THP or MOM ethers with this phosphine reagent in CH2C12 at 25° results in cyclization to tetrahydropyrans. 

In 1997, Tokitoh, Okazaki and coworkers reported evidence for the generation of a kinetically stabilized 1-germaallene 20725,123. It was synthesized by two different synthetic approaches as shown in Scheme 63. One is the dechalcogenation reaction of the corresponding alkylidenetelluragermirane 205 with a phosphine reagent, and the other is the reduction of (l-chlorovinyl)chlorogermane 206 with f-butyllithium. 

The synthesis of the first stable compound containing a Bi=Bi double bond, (Tbt)Bi=Bi(Tbt) (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl), (10), was achieved by a rather involved procedure concerning the deselenation of triselenatribismane with a phosphine reagent." The key intermediate in this synthesis a triselenatribismane. The synthetic procedure continued with the treatment of this intermediate with an excess amount of hexamethylphosphoms triamide and heating for 12h. Finally, the dibismuthene was isolated as deep purple single crystals. This was a significant discovery a homonuclear double bond involving the heaviest stable (i.e. nonradioactive) element on the periodic table. 

The asymmetric allylation of achiral aldehydes with a novel silver complex has recently been reported (Scheme 10-51) [90]. Initially, it was shown that the silver-promoted reaction of allyltributylstannane with benzaldehyde could be accelerated by triphenylphosphine. A survey of various chiral phosphine reagents and silver salts identified the combination of binap and AgOTf as optimal. The reaction of benzaldehyde and allyltributylstannane promoted by 5 mol% of the binap-AgOTf... 

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