Phosphines, alkylation polymer-supported

Alkyl chlorides , acid chlorides (1,1247). The conversion of alcohols into alkyl chlorides and of adds into acid chlorides with (CsHslsP and CCU proceeds more rapidly when the phosphine is polymer supported. One factor contributing to the rate increase may be the close proximity of the phosphorus-containing residues. 

An interesting approach to develop an asymmetric allylic alkylation catalyst by using a peptide-based phosphine hgand was examined by Gilbertson (Scheme 3.70) [135]. Phosphine-sulfide amino acid 211 was incorporated into a peptide sequence on a polymer support After reduchon of the phosphine sulfide to phosphine, the polymer-supported pephde sequence having phosphine-(support-Gly-Pps-D-Ala-Pro-Pps-D-Ala-Ac) was prepared. The complex of the peptide with Pd was uhhzed for the asymmetric addition of dimethyl malonate 202 to 3-acetoxycy-clopentene 212 to give 213 in 59% yield and 66% ee. 

All the polymers of Table III have been applied for the epoxidation of olefins with alkyl hydroperoxides. For example, the polymers with iminodiacetic acid or diethylene triamine groups were used for the regioselective epoxidation of (E)-geraniol with t-BuOOH to the 2,3-epoxide (225), whereas the Mo anchored to the diphenylphosphinopolystyrene catalyst is used in the epoxidation of cyclohexene with t-BuOOH (228). The polymer-supported molybdenyl thioglycolate has also been used for the catalytic oxidation of thiols and phosphines with air or pyridine N-oxide as the oxidant (234). 

The need for new classes of strong non-ionic, non-nucleophilic bases has led Palacios and co-workers to investigate ylide (101) and its polymer-supported analogue (102) in this capacity. It was found that ylides (101) and (102) acted as versatile bases for selective A -alkylation reactions of P-amino phosphine... 

Uozumi and coworkers prepared phosphine/palladium complexes supported on polyethylene glycol-polystyrene graft polymer. - This amphiphilic resin-supported palladium complex eftidently catalyzed the alkylation of allylic acetates in water with various nucleophiles including 1,3-dicarbonyl compounds, amino acids, sodium azide, sodium sulfinate, phenylboronic acid, and sodium tetraphenylborate to give the corresponding allylic-substituted products in quantitative yields. 

In recent years organic chemists have shown considerable interest in polymer-supported reactions. Such reactions have several attractive features one of which is that isolation of the products is simplified because the supported species can easily be filtered off from the non-supported species. This article is concerned with olefin synthesis by phase transfer catalysed polymer-supported Wittig reactions. Two main types are considered, those in which the phosphine is the supported species (see Scheme 1) and those in which the alkyl halide is the supported species (see Scheme 2). An example of the third type in which the carbonyl compound is the supported species is also given ... 

A similar purification method for the alkene product employs a polymer-supported reagent. Westman has developed a one-pot Wittig reaction of alkyl halides with aldehydes mediated by a polymer-supported phosphine and potassium carbonate under microwave irradiation (Scheme 32) [147]. Recently,... 

Synthesis of Vitamin D3 Core 248 Phosphine oxide 245 (1.1 equiv) was dissolved in anhydrous THF, cooled to —50°C, and treated with nBuLi (1.0 equiv) under argon. The mixture was then transferred via cannula to a solution of resin-bound ketone 244 (0.72 equiv) in anhydrous THF and reacted at —40°C to — 10°C for 3 hours to yield immobilized triene 246. Concomitant alkylation and cleavage from the polymer-support occurred via a copper-promoted Grignard reaction with 247 at room temperature for 3 hours. The crude protected product was then immediately treated with CSA in methanol and water at room temperature for 6 hours to afford vitamin D3 analog 248 in 47% yield (from 244). 

Metallocarbenes have been implicated in the iridium-catalysed isomerization of branched hydrocarbons, such as that of 2-methylpentane (1) to 3-methylpentane (3). Studies with C-labelled (1) support a mechanism which proceeds via (2) as intermediate. Polymer-bound triphenylphosphine-lithium diorganocuprates may offer advantages in the Wurtz-type coupling of alkyl halides, in that work-up is easier and the product is not contaminated with residual tertiary phosphine. However, yields in general are comparable with those from the corresponding homogeneous reagents. ... 

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