Triphenylphosphine polymer-bound

Preparation of 4-(2-hromoethyl)phenol 200 [125] A solution of 4-(2-hydrox-yethyl)-phenol 201 (25 g, 0.181 mol, 1 equiv.), carbon tetrabromide (90.14 g, 0.272 mol, 1.5 equiv), and diphenylphosphino-polystyrene 33 (151 g, 0.453 mol, 2.5 equiv. triphenylphosphine polymer-bound 3mmolg Fluka Cat No. 93 093) in CH2CI2 (250 mL) was stirred at 40 °C for 3.5 h. The solution was then filtered, the resin was washed with CH2CI2 (3 x 175 mL), and the combined filtrate and washings were concentrated under reduced pressure to yield the title compound 200 as a white soHd (quantitative). 

Triphenylphosphine polymer bound <3 mmol/g, available from Fluka Cat. No. 93093. 

Dehydration of (3-nitro alcohols using DCC gives a mixture of E/Z nitroalkenes 48 The pure (E)-isomers are obtained on treatment with catalytic amounts of triethylamine or polymer-bound triphenylphosphine (TPP) (Eq. 3.28).51 When (Z) nitroalkenes are desired, the addition of PhSeNa to the E/Z mixture and protonation at -78 °C followed by oxidation with H202 gives (Z)-nitroalkenes (Eq. 3.29).52... 

Weik and Rademann have described the use of phosphoranes as polymer-bound acylation equivalents [65]. The authors chose a norstatine isostere as a synthetic target and employed classical polymer-bound triphenylphosphine in their studies (Scheme 7.54). Initial alkylation of the polymer-supported reagent was achieved with bromoacetonitrile under microwave irradiation. Simple treatment with triethyl-amine transformed the polymer-bound phosphonium salt into the corresponding stable phosphorane, which could be efficiently coupled with various protected amino acids. In this acylation step, the exclusion of water was crucial. 

Scheme 7.120 Palladium-catalyzed isonitrile formation utilizing polymer-bound triphenylphosphine.

Figure 8. 31P-CP/MAS solid-state spectrum of polymer-bound (polystyrene cross-linked with 2% divinylbenzene) triphenylphosphine (a), 31P-CP/MAS solid-state spectrum of cis-[PtCl2(PPht-C6H -CH—CH2)2] (referenced to external 85% Hs POJ (b), 31P-CP/MAS solid-state spectrum of a copolymer of 65% styrene, 31% divinylbenzene and 4% cis-/PtCl2(PPh2-C6H -CH CH2)z] after soxhlet extraction (c) and 31P-CP/MAS solid-state spectrum of c s-[PtCl(PPhs)2, (N P )] ClOf after soxhlet extraction (d). All spectra referenced to external 85% HsPOk. (Reproduced from Ref. 21. Copyright by American Chemical Society.)...

An efficient solid-phase synthesis of [l,2,4]triazolo[l,5-7]indazoles has been described starting from bis(azide) 367. The coupling of this compound with polymer-bound triphenylphosphine gives compound 368. This unprecedented bis(iminophosphorane) reacts with various isothiacyanates to give the corresponding iminophosphoranes 215 (unreported yields) attached to the resin (Scheme 37) <2000SL1411>. 

Several methods are available to access glycosyl iodides (Scheme 2.50). Anomeric hemiacetals bearing diverse protecting groups (Bn, Bz, Ac, N3, CMe2) upon treatment with a polymer-bound triphenylphosphine-iodine complex and imidazole can be converted into a-glycosyl iodides [179]. The precipitated by-products,... 

The polymer bound triphenylphosphine oxide, lb, is readily converted to the ditriflate, 2b, following Hendrickson and Schwartzman s procedure for the synthesis of triflyltriphenyl-phosphonium triflate, 2a, (8). Much of our work has been the exploration of the monomeric system, first the conversion of the alcohol to ROP(Ph)3+OTf- and the subsequent reactions of these with various nucleophiles. 

The polymer bound triphenylphosphine oxide was synthesized using established techniques from a macro reticular DVB/styrene copolymer, Amberlite XE-305 (10). The phosphorus content was determined gravimetrically using the Kjeldahl method (11). 

A modification of GSR has been reported by Classon and co-workers.190 The idea remains the same create a covalently bound phosphorus cation and displace with a nucleophile—in this case, a halogen. Both bromine and iodine have been used.190 Three different systems were evaluated (1) chlorodiphenylphophine, iodine-bromine, and imidazole (2) p-(dimethylamino)phenyldiphenylphosphine, iodine-bromine, and imidazole or (3) polymer-bound triphenylphosphine, iodine-bromine, and imidazole. The last two were found to be very similar to just triphenylphosphine itself, and displayed reactivity inferior to the first system. The polymer-bound reagent does allow for easier removal of triphenylphosphine oxide produced in the course of the reaction. As with the original procedure, and consistent with a Sn2 mechanism, inversion of configuration occurred. Again, as with the original method vicinal diols were readily converted into alkenes.191 This... 

Oxidation of thiochroman-4-ol to thiochroman-4-one can be achieved without competing Pummerer rearrangement using triphenylphosphine dihalides in DMSO (Equation 92) <2002TL8355>. This oxidation has also been achieved using polymer-bound periodinane (82% yield) <1999T6785> and 2-iodoxybenzoic acid is also effective (92%) <1995JOC7272>. 

Complexation of the three silver salts Ag(CBnH12), Ag(CBnH6Br6), and Ag(OTf) to polymer bound triphenylphosphine also yielded active catalyst systems. The polymer-bound catalyst could be recycled 3 times with no loss of activity. Dimeric complexes [e.g., [Ag(PPh3)2(CBnH12)]2] were significantly poorer catalysts. 

Polymer-supported Wittig reagents have recently been developed as an extension to the traditional reagents.29 For example, polystyryldiphenylphosphine has been developed in an attempt to replace the use of triphenylphosphine in the preparation of phosphoranes (see Protocol 1). The hope is that these polymer-bound regents will overcome the practical problem of removing the triphenylphosphine oxide by-product formed in Wittig reactions. Polymer supported phosphonates and Wittig substrates have also been prepared for use in solid phase synthesis and combinatorial chemistry.30... 

Allyl protection of terminal a-carboxy groups has been used in convergent syntheses of N-linked glycopeptides on a solid support.PI For instance, the polymer-bound trisaccharide pentapeptide allyl ester 12 (Scheme 7) is built up by condensation of the polymer-linked trisaccharide with Z-Ala-Ile-Asp-Ile-Ser(Bzl)-OAl. Further conversion into the polymer-bound trisaccharide octapeptide derivative 14 is achieved by cleavage of the allyl ester with tetrakis(triphenylphosphine)palladium and A,A-dimethylbarbituric acid to give 13, followed by condensation with H-Asp(OMob)-Leu-Thr(Bzl)-OAl. The presence of the allyl ester group at the C-terminus of the octapeptide provides the opportunity for further chain elongation. 

The reactions of thionyl chloride and phosphorus halides, also in their polymer-modifled form, involve the formation of hydrogen halide and cannot, therefore, be applied without complications to acid sensitive compounds. The combination of triphenylphosphine and tetrachloromethane as reagent provides conditions under which, for instance, pelargonic acid can be converted to the acid chloride in good yield according to equation (5). ° This method has been recently applied to polymer-bound triphenylphos-phine. Table 2 lists some examples of acids treated in this manner. 

Traceless Synthesis Using Polymer-Bound Triphenylphosphine... 

A Hbrary of aryl ethers has been prepared by Mitsunobu etherification by stirring a mixture of polymer-bound triphenylphosphine (1.5 equiv.), DEAD (1.5 equiv.), the appropriate alcohol (1.5 equiv.), and a phenol (1 equiv.) in dichloromethane at room temperature for 4-12 h ]37]. As described, the resin was filtered off, the solvent was evaporated, and the DEAD-derived side product was removed by short-path silica gel column chromatography. 

The use of polymer-bound triphenylphosphine has also been described in combination with carbon tetrachloride for the condensation of carboxyhc acids with primary amines to give amides via the corresponding in situ formed mixed phosphinic anhydride, and for the conversion of aliphatic alcohols to the corresponding alkyl chlorides [38]. 

Polymer-supported triphenylphosphine ditriflate (37) has been prepared by treatment of polymer bound (polystyrene-2% divinylbenzene copolymer resin) triphenylphosphine oxide (36) with triflic anhydride in dichloromethane, the structure being confirmed by gel-phase 31P NMR [54, 55] (Scheme 7.12). This reagent is effective in various dehydration reactions such as ester (from primary and secondary alcohols) and amide formation in the presence of diisopropylethylamine as base, the polymer-supported triphenylphosphine oxide being recovered after the coupling reaction and reused. Interestingly, with amide formation, the reactive acyloxyphosphonium salt was preformed by addition of the carboxylic acid to 37 prior to addition of the corresponding amine. This order of addition ensured that the amine did not react competitively with 37 to form the unreactive polymer-sup-ported aminophosphonium triflate. 

These reagents can be used in the same way as triphenylphosphine dichloride (equations 1-V). Each reaction leads to the polymer-bound corresponding... 

In order to introduce diversity at the PI position, intermediate 73a was constructed from the corresponding polymer-bound pyrrolidine amide 80 (Scheme 18). Anchoring of pyrrolidine amide 78 (MMT = mono-/ -meth-oxytrityl), which was prepared in four steps (76% overall yield) from commercially available (S)-methyl ester isopropylideneglycerate (77a) to (ben-zyloxy)benzyl bromide resin 79 (prepared from Wang resin by treatment with carbon tetrabromide and triphenylphosphine [150]), proceeded in 84% loading yield with minimal racemization (<2%) [151]. 

Preparation.—Conventional quaternization reactions of phosphines with alkyl halides have been used for the preparation of chiral P-hydroxyalkylphosphonium salts for use in prostaglandin synthesis and of the salts (111), (112), and (113). This approach has also been used for the preparation of polymer-bound phosphonium salts for use in subsequent Wittig reactions and of a range of co-dialkylaminoalkylphosphonium salts. The salt (114), of limited thermal stability, is formed on treatment of the parent phenylphosphaferrocenophane (67, R = Ph) with iodomethane. The oxonium salt (115) is converted into the mixed onium salt (116) on treatment with triphenylphosphine. A range of... 

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