Highly efficient allyl cross-coupling reactions of allylindiums with organic electrophiles

This paper describes highly efficient allyl cross-coupling reactions of allylindiums with organic electrophiles such as aryl and vinyl triflates, vinyl halides, dibromoolefin, and alkynyl iodide. The reactions were carried out using 4 mol % Pd(PPh3)4 in the presence of 3 equiv of LiCl in DMF at 100 degrees C under a nitrogen atmosphere. Allylindium, generated from the reaction of 1 equiv of indium with 1.5 equiv of allyl halide, gave the best result as a coupling partner. The present method is mild and simple to apply, and it produces a diverse range of allylic compounds in good to excellent yields.     

Generation of allyl Grignard reagents via titanocene-catalyzed activation of allyl halides

A protocol for the generation of allyl Grignard reagents via the catalytic activation of allyl halides is described herein. Subsequent nucleophilic addition to carbonyl derivatives provided the desired homo allylic alcohols in excellent yields (84-99%). Evidence suggests that titanocene dichloride catalyzes the formation of an allyl Grignard species which reacts solely with the carbonyl electrophile as evidenced by the complete absence of Würtz coupling. This methodology will have wide-ranging applicability in the generation of highly reactive organometallic reagents.     

Pd-catalyzed olefination of perfluoroarenes with allyl esters

An efficient Pd(II)-catalyzed direct olefination of perfluoroarenes with allyl esters is demonstrated. Under the typical conditions, the coupling reaction of fluorinated-arenes with allylic esters proceeded via a β-H elimination rather than a β-OAc elimination to give the corresponding γ-substituted allylic esters.     

Inter- and intramolecular palladium-catalyzed allyl cross-coupling reactions using allylindium generated in situ from allyl acetates, indium, and indium trichloride

Inter- and intramolecular palladium-catalyzed allyl cross-coupling reactions using allylindium generated in situ by treatment of allyl acetates with indium and indium trichloride in the presence of Pd(0) catalyst and nBuNMe(2) in DMF were successfully demonstrated. Allylindium species generated in situ by reductive transmetalation of pi-allylpalladium(II) complexes, obtained from a variety of allyl acetates in the presence of Pd(0) catalyst together with indium and indium trichloride, were found to be capable of acting as effective nucleophilic coupling partners in Pd-catalyzed cross-coupling reactions. A variety of allyl acetates such as but-1-en-3-yl acetate, crotyl acetate, and 2-methylallyl acetate afforded the corresponding allylic compounds in good yields in cross-coupling reactions. Various electrophilic cross-coupling partners such as aryl iodides and vinyl bromides and triflates participate in these reactions. Not only intermolecular but also intramolecular Pd-catalyzed cross-coupling reactions work equally well to produce the desired allylic coupling products in good yields.     

Pd-catalyzed olefination of furans and thiophenes with allyl esters

A direct Pd(II)-catalyzed olefination of furans and thiophenes with allyl esters is demonstrated. Under the typical conditions, the dehydrogenative Heck coupling reactions of heteroarenes with allylic esters proceeded via a β-H elimination rather than a β-OAc elimination to give the corresponding γ-substituted allylic esters.     

Rearrangements of the carbanions derived from allyl benzyl thioether

The metalation of allyl benzyl thioether involves the benzylic or the allylic hydrogens. The benzylic carbanion undergoes a rapid[2,3] sigmatropic shift whereas the allylic carbanion gives rise to various rearrangements, among them migration of the allylic unit to the para position with allylic inversion. The temperature dependence of the ratio of products arising from the benzylic carbanion vs those from the allylic carbanion shows that the allylic-to-benzylic carbanion transformation occurs only under special conditions: (a) with slow addition of the base; (b) with thioether in excess relative to the base, and (c) on raising the temperature of the reaction medium from ?78° to ?15°. In the last instance, the proton transfer is intramolecular as shown with labeled thioethers. The extent of the different rearrangements depends on the temperature and solvent. A choice of mechanism cannot be made at this time for the para migration 5→9a. A leaving group effect on the reaction regioselectivity of the carbanion from allyl methyl thioether with benzyl halides has been noticed. The presence of dibenzyl indicates that, in addition to S_N2 reactions, some electron transfer process is occurring.     

Characteristic polymerization behaviour of microgel-like poly(allyl methacrylate) microspheres

In the emulsion polymerization of allyl methacrylate (AMA), the reactive crosslinked polymer microspheres or microgel-like polymers with abundant pendant allyl groups were easily obtained because AMA possesses two types of vinyl groups, methacrylic and allylic double bonds, having greatly different reactivities. The resulting microgel-like poly(allyl methacrylate) microspheres (PAMA microspheres) were characterized by light scattering and viscometry. Then, the characteristic polymerization behaviour of PAMA microspheres was explored by the copolymerizations with diallyl terephthalate (DAT) and allyl benzoate (ABz).     

Ruthenium-catalysed linear-selective allylic alkylation of allyl acetates

The regioselectivity in the ruthenium-catalysed allylic alkylation of mono substituted allyl acetates with the malonate anion was highly controlled by Ru3(CO)12 with 2-(diphenylphosphino)benzoic acid, and the linear-type alkylated product was obtained.     

Kinetics of the HBr-catalyzed photoisomerization of the allyl halides

The kinetics of the gas phase bond isomerization of allyl fluoride, allyl chloride and allyl bromide, catalyzed by HBr and ultraviolet light, has been studied in the temperature range of 150–250° and at pressures of 3.5 to 50 mm. The reactions are very clean, first order in allyl halide and HBr, and have a light intensity exponent of unity. A quantum yield for allyl chloride of 3200 indicates a chain reaction. Dilution with inert gases is almost without effect, indicating that excited state intermediates are not involved. A small wall effect is observed. The evidence indicates a free radical reaction, involving hydrogen abstractions by bromine atoms, with replacement at the other end of the allylic radical.     

金属锡作用下烯丙基溴与α,β-不饱和醛、酮和醌的反应

金属锡作用下烯丙基溴与α,β-不饱和醛区域选择性加成,只生成1,2-加成产物。烯丙基卤代物和锡与1,4-醌类反应,不经分离,直接氧化可得到烯丙基取代醌类。     

Synthesis of allyl selenides by palladium-catalyzed decarboxylative coupling

This communication details the Pd-catalyzed decarboxylation of selenocarbonates; use of a chiral nonracemic catalyst affords enantioenriched allyl selenides which undergo stereospecific [2,3]-sigmatropic rearrangements to form enantioenriched allylic amines and chlorides.     

Gold-catalyzed rearrangement of substituted allyl aryl ethers

Triphenylphosphinegold(I) complexes catalyze the Claisen-type rearrangement of aryl allyl ethers to the corresponding branched and linear products. The product distribution depends on the olefin geometry of the allylic ether. Stereochemical transfer experiments support an ionic mechanism.     

A novel synthesis of allyl vinyl ethers

Base-promoted reaction of dimethyl diazomethylphosphonate ($\text{2}$) with aliphatic ketones in the presence of allylic alcohols affords aldehydic allyl vinyl ethers ($\text{3}$).     

A theoretical study of substituted allyl anions

CNDO/2 calculations have been used to optimise the geometry of the allyl anion. Electron-withdrawing substituents are found to decrease the proton affinities of allylic anion, with the trans-substituted anion being the more stable. However when the only substituent on the anion is an alkyl group then the cis anion is the more stable. The calculated proton affinities of several monosubstituted allyl anions and the electron densities of the methyl hydrogens in the hydrocarbons are both found to correlate with the Hammett substituent constants.     

Palladium-catalyzed amination of allyl alcohols

An efficient catalytic amination of aryl-substituted allylic alcohols has been developed. The complex [(η(3)-allyl)PdCl](2) modified by a bis phosphine ligand, L, has been used as catalyst in the reaction that afforded a wide range of allyl amines in good to excellent yield under mild conditions.     

Palladium-catalyzed electrophilic substitution of allyl chlorides and acetates via bis-allylpalladium intermediates

Palladium-catalyzed electrophilic allylic substitution of functionalized allyl chlorides and allyl acetates can be achieved in the presence of hexamethylditin under mild and neutral reaction conditions. This efficient one-pot procedure involves palladium-catalyzed formation of transient allylstannanes followed by generation of a bis-allylpalladium intermediate, which subsequently reacts with electrophiles. Using this catalytic transformation, various aldehydes and imines can be allylated providing highly functionalized homoallyl alcohols and amines. Furthermore, tandem bis-allylation reactions could be performed by employing tosyl isocyanate and benzylidenemalonitrile as substrates. A particularly interesting mechanistic feature of this reaction is that palladium catalyzes up to three different transformations in each catalytic cycle. Various allylic functionalities, including COOEt, CONH(2), COCH(3), CN, Ph, and CH(3), are tolerated in the catalytic reactions due to the application of neutral and mild reaction conditions. The substitution reaction occurs with very high regioselectivity at the branched allylic terminus. Moreover, in several reactions, a high stereoselectivity was observed indicating that this new catalytic process has a high potential for stereoselective synthesis. The regioselectivity of the reaction can be explained on the basis of DFT calculations. These studies indicate that the allylic substituent prefers the gamma-position of the eta(1)-allyl moiety of the reaction intermediate.     

Stannylated allyl carbonates as versatile building blocks for the diversity oriented synthesis of allylic amines and amides

Stannylated allylic carbonates are suitable substrates for Pd-catalyzed allylic aminations. In DMF and with [allylPdCl](2) as catalyst the stannylated allyl amines formed can be directly coupled with electrophiles according to the Stille protocol, giving rise to highly functionalized building blocks in excellent yields.     

Transition metal σ-complexes in organic synthesis. 4. Cross coupling of allyl esters and allyl aryl sulfones with organotitanium compounds in the presence of palladium complexes

Conclusions The reactions of organotitanium compounds PhTi(OPr-i)₃ and MeTi(OPr-i)₃ with allyl acetates, allyl phenyl ethers, allyl aryl sulfones, and allylic tosylates and mesylates are catalyzed by Pd complexes and lead to the formation of cross-coupling products.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2159–2166, September, 1988.     

Polymerization of allyl esters of unsaturated acids. V. Cyclopolymerization of methyl allyl fumarate

The kinetics of radical polymerization of methyl allyl fumarate (MAF) is discussed in terms of cyclopolymerization and compared with the polymerization results of methyl allyl maleate (MAM) as a cis isomer. In the polymerization of MAF, the rate and degree of polymerization were quite enhanced compared with MAM, and gelation occurred at low conversion. The content of the unreacted allylic double bonds of the MAF polymer was quite large; whereas those of the unreacted fumaric double bonds and the cyclic structural units showed reverse tendencies. Only a slight presence of a five-membered ring was observed in the MAF polymer. The cyclization constants K_A and K_V, the ratios of the rate constants of the unimolecular cyclization reaction to those of the bimolecular propagation reaction of the uncyclized allylic and fumaric radicals, were estimated to be 2.73 and 1.48 mole/liter, respectively. These values suggest the great difference in the cyclopolymerization behavior between two isomeric monomers. These results are discussed in detail in connection with the high reactivity of the fumaric double bond compared to the maleic double bond. In addition, the formation mode and the sequence distribution of the structural units of the polymer produced are discussed on the basis of these analytical results. Thus, for the MAF polymer obtained in the bulk polymerization, about 60% of the cyclic structure can be formed via the intramolecular attack of the uncyclized fumaric radical on the allylic double bond, as opposed to the case of MAM via the predominant intramolecular attack (ca. 90%) of the uncyclized allylic radical on the maleic double bond; these results and the low probability for the succession of cyclic structures and the rather high probability of a vinyl-to-vinyl addition are presented.     

Thermolysis and photolysis of arylchlorodiazirines in allyl bromide

p-Chlorophenylchlorocarbene reacts with allyl bromide to form the expected cyclopropanes. In the case of p-nitrophenylchlorocarbene, a small amount of insertion product is also formed in addition to the cycloadducts. The formation of the insertion product is attributed to the attack of the carbene on the bromine atom followed by intramolecular allylic rearrangement.