Allylic diphenylphosphinates

Analogously to the phosphorylation of alcohols with phosphoric azolides the phos-phinylation is carried out by means of phosphinic azolides (CH2CI2/C2H5OC2H5). In the following case a I2/C2H5OC2H5) protonated diphenylphosphinic imidazolide is used to give the allylic diphenylphosphinic esters in good yields ... 

In 2002, Grubbs and co-workers reported the first CM reactions of allyl phosphines.In an initial reaction, subjecting allyl diphenylphosphine to catalyst 5 (5 mol%) failed to produce any of the desired cross-product. However, by protecting the phosphine as its borane complex, CM reactions could be achieved in good yield with high E-selectivity (Equation (5)). Notably, catalyst 5 failed to dimerize borane-protected vinyl diphenylphosphine. This result was attributed to substrate trapping of the catalyst as an unreactive Fischer carbene, a situation analogous to that observed in the CM reactions of alkyl vinyl ethers. 

An additional example utilizing phosphorus nucleophiles employs lithium diphenylthiophosphides and allyl carboxylates and yields allylic diphenylphosphine sulfides (equation 66).2 1... 

The anions generated from geometrically pure allylic diphenylphosphine oxides, e.g. (102), react with carbonyl compounds to afford conjugated dienes in which the geometry of the original allyl system is preserved. ... 

Allylic diphenylphosphinates The esterification is mediated by imidazole. The salt is probably the active reagent. 

Allylic diphenylphosphine oxides undergo 1,3-dipolar cycloadditions with nitrile oxides to give A -isoxazolines (70) with ann -preferred stereoselectivities of up to 5 1.37 Separate reduction of y -and anti-(70) to the hydroxy amines (71), followed by Wittig-Horner elimination provides stereoselective syntheses of the homoallylic amines (72) (Scheme 9). A study of the effect of substituents on phosphorus on the diastereoselectivity in the cycloaddition of nitrones to vinylphosphine oxides (73) and sulphides (74) has been reported.38 In certain cases diastereoselectivities of >90% were achieved. 

In benzene solution the entropy of activation is — 14eu. Isomerization of deuterium-labeled allyl diphenylphosphinate and a- and y-methylallyl dipheny 1-phosphinates showed that the reaction proceeds with complete inversion of allylic structure and is effectively irreversible. The activation parameters and stereospecificity of this reaction are consistent with a concerted, cyclic mechanism. 

Carbon-phosphorus bonds are formed by the Pd-catlyzed allylation of various phosphorus compounds (Scheme 13). The reaction of l-acetoxy-2-cyclohexene with LiPPh2 in refluxing THF provides an allylic phosphine in low yield (<15%). The phosphine produced deactivates the catalyst by coordination, which lowers the yield. In contrast, the reaction of LiP(S)Ph2 with l-acetoxy-2-cyclohexene takes place at room temperature to give allylic diphenylphosphine sulfides in 85% yield. ° Pd-catalyzed Michaelis-Arbuzov reaction of cinnamyl acetate with trimethyl phosphite affords a dimethyl allylic phospho-nate. With the reaction conditions being rather severe, this method may not be applicable to an allylic acetate that can produce a conjugated diene via /3-hydride elimination from the intermediate 7r-allylpalladium complex. 

One of the main applications of dendrimers is in catalysis allowing easy recycling of the homogeneous catalyst by means of nanofiltration. Carbosilane dendrimers functionalized with diphenylphosphine groups at the periphery have been synthesized and characterized. Palladium complexes of these dendrimers have been used as catalysts in the allylic alkylation reaction. These dendrimeric catalysts can be used in a continuous process using a membrane reactor.509... 

Another reaction performed in the dead-end reactor discussed before, is the allylic amination of 3-phenyl-2-propenyl-carbonic acid methyl ester with morpholine. [30] First and second generation commercially available DAB-dendrimers were functionalized with diphenylphosphine groups (Figure 4.13). Two different membranes were used, the Nadir UF-PA-5 (ultrafiltration) and the Koch MPF-50 (former SELRO) (nanofiltration), which gave retentions of 99.2% and 99.9% respectively for the second generation functionalized dendrimers. 

Van Leeuwen et al. used several generations of carbosilane dendrimers with 4, 8, 24, and 36 diphenylphosphine end-groups (Figure 4.15) for the allylic alkylation reaction of allyl trifluoracetate with sodium diethyl 2-methylmalonate.[31]... 

Stereoselective allylic alkylations have been carried out with the aid of palladium catalysts. The 17-(Z)-ethylidene groups of steroids (obtained from the ketones by Wittig olefination) form n-allyl palladium complexes in the presence of copper(n) salts (B.M. Trost, 1974, 1976). Their alkylation with dimethyl malonate anions in the presence of 1,2-ethane-diylbis[diphenylphosphine] (— diphos) gives a reaction exclusively at the side chain and only the (20S) products. If one starts with the endocyclic 16,17 double bond and replaces an (S)-20-acetoxy group by using tetrakis(triphenylphospbine)palladium,the substitution occurs with complete retention of configuration, resulting from two complete inversions (B.M. Trost, 1976). 

The group of Van Leeuwen has reported the synthesis of a series of functionalized diphenylphosphines using carbosilane dendrimers as supports. These were applied as ligands for palladium-catalyzed allylic substitution and amination, as well as for rhodium-catalyzed hydroformylation reactions [20,21,44,45]. Carbosilane dendrimers containing two and three carbon atoms between the silicon branching points were used as models in order to investigate the effect of compactness and flexibility of the dendritic ligands on the catalytic performance of their metal complexes. Peripherally phosphine-functionalized carbosilane dendrimers (with both monodentate... 

Scheme 7 Schematic pathway of the synthesis of diphenylphosphine-functionalized car-bosilane metallodendrimers applied in allylic alkylation reactions...

The key step in the synthesis of triazonines with pendant diphenylphosphine arms is the free radical addition of Ph2PH across the alkene double bond (Equation 10) <1996CC1817>. This is accomplished in quantitative yield by photolysis under strictly anaerobic conditions using a mercury lamp. The method was not restricted to allyl substituents longer-arm alkenes react in an identical manner, although more slowly, yielding phosphines with longer alkyl, for example G-5, chains. 

Macrocyclization by allylation-alkylotion. The key step in a synthesis of the antibiotic A26771B (3) is cyclizationof the substrate 1 using O.N-bis(trimethylsilyl)acetamide (1, 61 2, 30 3, 23-24) as base and Pd[P(ChH,),]4 as catalyst. In addition a bidcntate phosphorus ligand is essential. The highest yields were obtained with 1,4-bis(diphenylphosphine)butane (dppb). 

Thus indirect electroreduction of haloethers 69 and 71 led to the corresponding cyclized tetrahydrofuran derivatives 70 and 72, respectively, in good yields via 5-exo-trig mode [23], On the other hand, A -allyl-a-bromoamide 73 gave the corresponding pyrrolidone 74 in DMF in the presence of 2 equiv of a hydrogen donor, diphenylphosphine, whereas A -allyl-cx-iodoamide 75 gave the iodinated pyrrolidone 76 in acetonitrile [24],... 

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