Allylic phosphates, allylation

The relative reactivity of the derivatives follows the trend allyl carbonate > allyl phosphate > allyl acetate (see Equations 20.5-20.7)." This difference in reactivity allows for chemoselective substitutions of one allylic alcohol derivative over another. Other allylic electrophiles, such as allylic sulfonates, which undergo cleavage of the carbon-sulfur bond, allylic nitro compounds, which undergo cleavage of the C-N bond, - and allylic... 

Many examples of stereospecific allylation consistent with the above mechanism have been reported. As one example, the regioselective and highly diastereoselective allylation of the lactone 17 with the optically active allylic phosphate 16 proceeded with no appreciable racemization of the allylic part to give the lactones l8 and 19, and the reaction has been used for the synthesis of a polypropionate chain[26]. 

Allylation under basic conditions. Allylation can be carried out under basic conditions with allylic acetates and phosphates, and under neutral conditions with carbonates and vinyloxiranes. The allylations under neutral conditions are treated separately in Section 2.2.2.1 from those under basic conditions. However, in some cases, allylations of the same substrates are carried out under both basic and neutral conditions to give similar results. These reactions are treated together in this section for convenience. Allylic acetates are widely used for Pd-catalyzed allylation in the presence of bases tertiary amines or NaH are commonly used[6,7,4l]. As a base, basic alumina or ICF on alumina is conveniently used, because it is easy to remove by filtration after the reaction[42]. Allyl phosphates are more reactive than acetates. The allylation with 40 proceeds stepwise. At first allylic phosphate reacts with malonate and then allylic acetate reacts with amine to give 41(43]. 

Wylation under neutral conditions. Reactions which proceed under neutral conditions are highly desirable, Allylation with allylic acetates and phosphates is carried out under basic conditions. Almost no reaction of these allylic Compounds takes place in the absence of bases. The useful allylation under neutral conditions is possible with some allylic compounds. Among them, allylic carbonates 218 are the most reactive and their reactions proceed under neutral conditions[13,14,134], In the mechanism shown, the oxidative addition of the allyl carbonates 218 is followed by decarboxylation as an irreversible process to afford the 7r-allylpalladium alkoxide 219. and the generated alkoxide is sufficiently basic to pick up a proton from active methylene compounds, yielding 220. This in situ formation of the alkoxide. which is a... 

Allylic phosphates are used for carbonylation in the presence of amines under pressure. Carbonylation of diethyl neryl phosphate (389) affords ethyl homonerate (390), maintaining the geometric integrity of the double bond[244]. The carbonylation of allyl phosphate in the presence of the imine 392 affords the /3-lactam 393. The reaction may be explained by the formation of the ketene 391 from the acyl phosphate, and its stereoselective (2 + 2] cycloaddition to the imine 392 to give the /3-lactam 393(247],... 

The allylstannane 474 is prepared by the reaction of allylic acetates or phosphates with tributyltin chloride and Sml2[286,308] or electroreduction[309]. Bu-iSnAlEt2 prepared in situ is used for the preparation of the allylstannane 475. These reactions correspond to inversion of an allyl cation to an allyl anion[3l0. 311], The reaction has been applied to the reductive cyclization of the alkenyl bromide in 476 with the allylic acetate to yield 477[312]. Intramolecular coupling of the allylic acetate in 478 with aryl bromide proceeds using BuiSnAlEti (479) by in situ formation of the allylstannane 480 and its reaction with the aryl bromide via transmetallation. (Another mechanistic possibility is the formation of an arylstannane and its coupling with allylic... 

Propylene oxide-based glycerol can be produced by rearrangement of propylene oxide [75-56-9] (qv) to allyl alcohol over triUthium phosphate catalyst at 200—250°C (yield 80—85%) (4), followed by any of the appropriate steps shown in Figure 1. The specific route commercially employed is peracetic acid epoxidation of allyl alcohol to glycidol followed by hydrolysis to glycerol (5). The newest international synthesis plants employ this basic scheme. 

Allyl alcohol (propylene oxide) FB G Li phosphate 250 1 1.0 LHSV (15) 2.3... 

Pd(Ph3P)2Cl2(Bu3SnH, benzene) or cobalt carbonyl. The palladium method cleaves allyl esters, propargyl phosphates, and propargyl carbamates as well. 

Nucleophilic (8 2) reactions for the formation of benzyl, allyl, and certain alkyl phosphates [e.g., Me4N (R0)2P(0)0 and an alkyl halide in refluxing... 

One gram of 6,7-dihydro-5H-dibenz[c,e] azepine hydrochloride was dissolved in water, made alkaline with concentrated ammonia, and the resultant base extracted twice with benzene. The benzene layers were combined, dried with anhydrous potassium carbonate, and mixed with 0.261 g of allyl bromide at 25°-30°C. The reaction solution became turbid within a few minutes and showed a considerable crystalline deposit after standing 3 A days. The mixture was warmed VA hours on the steam bath in a loosely-stoppered flask, then cooled and filtered. The filtrate was washed twice with water and the benzene layer evaporated at diminished pressure. The liquid residue was dissolved in alcohol, shaken with charcoal and filtered. Addition to the filtrate of 0.3 gram of 85% phosphoric acid in alcohol gave a clear solution which, when seeded and rubbed, yielded 6-allyl-6,7-dihydro-5H-dlbenz[c,e] azepine phosphate, MP about 211°-215°C with decomposition. 

Allyl alcohol is produced by the catalytic isomerization of propylene oxide at approximately 280°C. The reaction is catalyzed with lithium phosphate. A selectivity around 98% could be obtained at a propylene oxide conversion around 25% ... 

Allylic Halides, Ethers, Phosphates, Ammonium Salts, Sulfonium Salts, Sulfones,... 

Scheme 30 represents the energy diagram for the photorearrangement shown in Scheme 29. Quenching of the triplet state of the sensitizer by the cis allyl phosphate, c/s-1, generates the triplet state, T , of the 1,2-biradical 2. The 1,2-biradical is trapped by the phosphorus atom to afford the triplet state, TP, of the spirophosphoranyl 1,3-biradical 3. Then, inter-system crossing generates the...

The Ag complex 121 in the presence of CuCl H O or CuCOTO CgHg catalyses the allylic alkylations of allyl phosphates by diaUcylzinc reagents with high enantiose-lectivity (Scheme 2.23). A copper complex 122 which is the precursor to the catalytic species was also isolated and structurally characterised (Figs. 2.21 and 2.22) [99]. 

Scheme 1.64 Cu-catalysed allylic substitution of cinnamyl phosphate with ZnEt2 in the presence of P-aminosulfonamide ligands.

Scheme 1.66 Cu-catalysed allylic alkylations of allylic phosphates with vinylalumi-num reagents in the presence of sulfur-containing diaminocarbene ligands.

High y-selectivity has been observed for allylic diphenyl phosphate esters.26a O... 

Allylic acetates and phosphates can be readily carbonylated.248 Carbonylation usually occurs at the less-substituted end of the allylic system and with inversion of configuration in cyclic systems. 

Allylic stannanes can be prepared from allylic halides and sulfonates by displacement with or LiSnMe3 or LiSnBu3.146 They can also be prepared by Pd-catalyzed substitution of allylic acetates and phosphates using (C2H5)2AlSn... 

The preparation of malonic acid monoesters has been demonstrated using the microbial nitrilase activity of Corynebacterium nitrilophilus ATCC 21 419, Gordona terrae MA-1, or Rhodococcus rhodochrous ATCC 33 025 to hydrolyze methyl cyanoacetate, ethyl cyanoace-tate, M-propyl cyanoacetate, isopropyl cyanoacetate, M-butyl cyanoacetate, tertbutyl cyanoacetate, 2-ethylhexyl cyanoacetate, allyl cyanoacetate, and benzyl cyanoacetate [96]. By maintaining the concentration of nitrile in a reaction mixture at <5 wt%, significant inactivation of the nitrilase activity was avoided for example, a total of 25 g of M-propyl cyanoacetate was added in sequential 5g portions to a lOOmL suspension of Rhodococcus rhodochrous ATCC 33 025 cells (OD630 = 5.6) in 50 mM phosphate buffer (pH 7.0) over 30h at 25 °C to produce mono-M-propyl malonate in 100% yield (Figure 8.17). 

Hoveyda and co-workers also tested optically active A-heterocyclic carbenes and their silver complexes in copper-catalyzed reactions of allylic phosphates with dialkylzincs.402 The ratios of Sn2 SN2 products were higher than 98 2 and the ee varied from 34% to 98%. 

The titanium reagent 1 reacts with allyl alcohol derivatives, such as halides, acetates, carbonates, phosphates, or sulfonates to afford allyltitanium complexes of the type (r 1-al-lyl)TiX(OiPr)2, as shown in Eq. 9.21 [42], As a variety of allylic alcohols are easily obtained,... 

The versatile Ti(II) chemistry available using preformed (alkene)Ti(OiPr)2 species was opened up by the discovery of the Kulinkovich cyclopropanation reaction [55]. Since 1995, Sato and collaborators have developed a wide range of elegant and synthetically useful reactions based on the Ti(OiPr)4/iPrMgCl reagent [56]. In particular, it was reported that the Ti(II) complex (q2-propene)Ti(OiPr)2, preformed from Ti(OiPr)4 and 2 equivalents of iPrMgCl, reacts with allylic compounds, such as halide, acetate, carbonate, phosphate, sulfonate, and aryl ether derivatives, to afford allyltitanium compounds as depicted in Scheme 13.27 [57]. 

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