Palladium-catalyzed allylation and deacylative allylation of 3-acetyl-2-oxindoles with allylic alcohols

The Pd-catalyzed allylation of 3-acetyl-2-oxindoles with allyl alcohol is performed using 3 mol% of Pd(dba)₂, rac-BINAP and BINOL phosphoric acid as catalytic mixture. This procedure allows the in situ synthesis of 3-allyl-2-oxindole by adding Triton B to the reaction mixture. The deacylative allylation of 3-acetyl-3-methyl-2-oxindoles with allylic alcohols is carried out with 3 mol% of Pd(OAc)₂, dppp and 1.5 equiv. of LiOtBu as base affording the corresponding 3,3-disubstituted 2-oxindoles in good yields. Both methodologies can be combined for the preparation of unsymmetrical 3,3-diallylated 2-oxindoles such as compound 7. The DaA must be carried out in the absence of oxygen in order to avoid the competitive formation of 3-alkyl-3-hydroxy-2-indoles. The later compounds can be easily obtained by deacylative oxidation of 3-alkylated 3-acetyl-2-oxindoles with LiOEt at rt under air.     

Highly efficient and regioselective allylic amination of allylic alcohols catalyzed by [Mo3PdS4] cluster

A highly efficient and regioselective allylation reaction of amines with allylic alcohols under mild conditions catalyzed by the cubane-type sulfido cluster [(Cp∗Mo)₃S₄Pd(dba)][PF₆] with H₃BO₃ as an additive has been developed. A variety of amines and allylic alcohols are investigated, and in the case of allylic alcohols bearing substituents at either α- or γ-position only linear allylic amination products are obtained.     

Regioselective synthesis of allylic sulfones by palladium-catalyzed denitro-sulfonylation of allylic nitro compounds

Allylic nitro compounds undergo denitro-sulfonylation catalyzed by Pd(PPh₃)₄ or Pd(PPh₃)₄ +NaNO₂ with PhSO₂Na·2H₂O to afford allylic sulfones regioselectively.     

S′H type reactions of substituted allylic compounds

S′_H reactions of allyl sulfides and halides with phenyl radicals are reported. Thermal decomposition of phenylazotriphenylmethane with allyl sulfides and bromide has been shown to give allylbenzene. This apparent substitution reaction involves attack of a phenyl radical on the terminal unsaturated carbon atom of the allyl sulfide; the reaction in α,α-dimethylallyl ethyl sulfide produced 2-methyl-4-phenylbutene-2. To estimate the relative reactivities of allylic substrates towards phenyl radicals, competitive reactions of phenyl radicals with allylic compounds and carbon tetrachloride were investigated. The data indicate that the radical formed by addition of a phenyl radical to the allylic sulfide looses thiyl radicals almost quantitatively.     

On the PdCl2-catalyzed synthesis of allylic azides and allylic sulfonamides from homoallylic alcohols

According to experimental and literature data, the one-pot formation of allylic azides or sulfonamides from catalytic amounts of PdCl₂, homoallylic alcohols and TMSN₃ or TsNH₂ occurs through CC migration followed by regioselective nucleophilic addition on the Pd^II-activated CC bond and β-OH elimination.     

N-Heterocyclic carbenes as ligands in palladium-catalyzed Tsuji–Trost allylic substitution

A Pd(0)-catalyzed allylic substitution (i.e., Tsuji–Trost reaction) using N-heterocyclic carbene as a ligand was investigated. It has been proven that an imidazolium salt 2d having bulky aromatic rings attached to the nitrogens in its imidazol-2-ylidene skeleton is suitable as a ligand precursor and that a Pd₂dba₃–imidazolium salt 2d–Cs₂CO₃ system is highly efficient for producing a Pd–NHC catalyst in this reaction. Allylic substitution using a Pd–NHC complex differed from that using a Pd–phosphine complex as follows: (1) the reaction using a Pd–NHC complex required elevated temperature (50 °C or reflux in THF), (2) allylic carbonates were inert to a Pd–NHC complex, and (3) nitrogen nucleophiles such as sulfonamide and amine did not react with allylic acetate. It was also found that allylic substitution with a soft nucleophile using a Pd–NHC catalyst proceeds via overall retention of configuration to give the product in a stereospecific manner, the stereochemical reaction course obviously being the same as that of the reaction using a Pd–phosphine complex.     

Ruthenium-catalyzed linear selective allylic aminations of monosubstituted allyl acetates

The ruthenium-catalyzed highly linear selective allylic amination of monosubstituted allylic acetates with secondary amines was developed. The regioselectivity was controlled by the Ru₃(CO)₁₂/2-DPPBA catalyst, and a linear-type aminated product was obtained as a single regioisomer.     

Regioselective synthesis of trifluoromethyl group substituted allylic amines via palladium-catalyzed allylic amination

The palladium-catalyzed regioselective allylic amination of α-trifluoromethylated allyl acetate occurred using Pd(OAc)₂/DPPE and [Pd(π-allyl)(cod)]BF₄/DPPF. The selective formation of the γ-product was attained by Pd(OAc)₂/DPPE, while the α-product was obtained using [Pd(π-allyl)(cod)]BF₄/DPPF.     

Efficient palladium–ferrocenylphosphine catalytic systems for allylic amination of monoterpene derivatives

Ferrocenylphosphines added to [Pd(µ‐Cl)(η³‐C₃H₅)]₂ dimeric precursor produce efficient catalysts to effect the allylic amination of terpenic allylacetates. Particularly convenient are tetrakis(diphenylphosphino)ferrocene and 1,1′‐bis(diphenylphosphino)ferrocene, which allow the amination of allylacetates with good to excellent selectivity, and have turnover numbers as high as 80 000, for instance, for the formation of allylaniline. Herein, we report on reactions that selectively transform geranylacetate, nerylacetate, linalylacetate and perillylacetate into the corresponding allylic amines. These preparative methods give facile access to various products of great potential industrial interest. Copyright © 2006 John Wiley & Sons, Ltd.     

Lewis acid-catalyzed oxidative rearrangement of tertiary allylic alcohols mediated by TEMPO

Two methods for the oxidative rearrangement of tertiary allylic alcohols have been developed. Most of tertiary allylic alcohols studied were oxidized to their corresponding transposed carbonyl derivatives in excellent to fair yields by reaction with TEMPO in combination with PhIO and Bi(OTf)₃ or copper (II) chloride in the presence or not of oxygen. Other primary oxidants of TEMPO such as PhI(OAc)₂, mCPBA, and Oxone^® were unsatisfactory giving the enone in modest to low yields.     

Palladium-catalyzed asymmetric allylic nucleophilic substitution reactions using chiral tert-butanesulfinylphosphine ligands

The asymmetric allylic alkylation of racemic 1,3-diphenyl-2-propenyl acetate 3 with dimethyl malonate proceeded smoothly in the presence of lithium acetate, BSA (N,O-bis(trimethylsilyl)acetamide), [Pd(η³-C₃H₅)Cl]₂, and chiral tert-butanesulfinylphosphine ligand 2c to give the allylic alkylation product in good yield and high enantiomeric excess (up to 93% ee), while the enantioselectivities of allylic amination of 3 with various amines were moderate (up to 76% ee).     

New synthetic routes to allylic germatranes

Allylic germatranes derived from triethanolamine can be prepared with moderate control of regioselectivity by two complementary routes. The first of these is through the preparation of the precursor allylic germanium trichlorides by a transmetallation reaction between germanium(IV) chloride and the corresponding allylic tributylstannanes followed by alcoholysis and reaction with triethanolamine. The second route is via the palladium-catalyzed hydrogermylation of conjugated dienes by germatrane, N(CH₂CH₂O)₃GeH. The former route gives mixtures of E and Z stereoisomers, whereas the second route gives exclusively Z products.     

Stereoselective synthesis of 2-C-methylene glycosides and disaccharides via direct allylic substitution of hydroxy group in benzylated glycals

InCl₃ efficiently catalyzes allylic substitution of the hydroxy group of 2-C-hydroxymethyl glycals to afford a diversity of 2-C-methylene alkyl and aryl glycosides as well as disaccharides in high yields. This protocol surpasses the existing methods for the synthesis of 2-C-methylene glycosides as it obviates the need for functionalizing the allylic hydroxy group of glycals. The interest of this methodology relies on the extremely mild conditions required even with a free hydroxyl group at the allylic position of the glycals and that too only with a catalytic amount of InCl₃. The reaction is fast (30 min.), stereoselective and is compatible with a variety of oxygenated nucleophiles including those possessing acid-labile groups. A mechanistic investigation on the direct formation of an α,α-(1→1)linked disaccharide derivative from 2-C-hydroxymethyl galactal reveals that the reaction proceeds through a domino Ferrier rearrangement followed by a facile 1,3-alkoxy migration.     

Ru3(CO)12-catalyzed intramolecular allylic transfer reaction of tethered carbonyl group and allylic acetate moiety

A ruthenium catalyzed intramolecular allylic transfer reaction of allylic acetates containing aldehydes or ketones to form cis-homoallylic cyclopentanols and cyclohexanols as a major component is described. The use of Ru₃(CO)₁₂ (1 mol %) to promote reaction results in a convenient procedure for intramolecular allylation of carbonyl functionalities.     

The Heck-type arylation of allylic alcohols with arenediazonium salts

The Heck coupling of ArN₂BF₄ with secondary allylic alcohols, carried out in methanol using Pd(dba)₂ as catalyst without extra ligands and base, leads to the corresponding β-arylated carbonyl compounds. Such conditions afford arylated acetals from primary allylic alcohols.     

Rhodium-catalyzed carbonyl allylations by allylic alcohols with tin(II) chloride

Rhodium complexes such as [RhCl(cod)]₂, [Rh(cod)₂]BF₄, and [Rh(cod)(CH₃CN)₂]BF₄ function as catalysts for carbonyl allylations by allylic alcohols with 1 equimolar amount of tin(II) chloride to each allylic alcohol and aldehyde in THF at 50 °C to produce the corresponding homoallylic alcohols.     

Some aspects of the chemistry of chlorofluoro-olefins which contain allylic chlorine atoms

Routes to perflouroallyl chloride, CF₂:CF.CF₂Cl, and to $\text{cis}$-and $\text{trans}$-1-chloro-hexafluoro-2-trifluoromethyl(but-2-ene), (CF₂Cl)(CF₃)C:CF.CF₃ are reported, and their susceptibility to attack by nucleophiles discussed; the allylic chlorine atoms in these olefins are the controlling factor in determining the products obtained.The conversion of 3-chloropentafluoropropene into a series of perfluoroallyl derivatives of general formula R.CF₂.CF:CF₂ [R = (CF₃)₃C-, CF₃O-, C₆F₅-, l-, MeO-, etc.] is described, and the further chemistry of 3-chloropentafluoropropene and its derivatives outlined.Water reacts rapidly with (CF₂Cl)(CF₃)C:CF.CF₃ to give CF₂:C(CF₃).CFCl.CF₃ or CF₃.CO.CH₂.CF₃. Methanol affords CF₂:C(CF₃).CFOMe.CF₃ and (MeOCF₂)(CF₃)C:CF.CF₃ as initial products, with subsequent secondary products such as CF₃.CFOMe.CH(CF₃).CF₂OMe, (CF₃)(MeO)C:C(CF₃).CF₃OMe, MeO.CF:C(CF₃).CFOMe.CF₃, (CF₃)(MeO)CF.CH(CF₃).CO₂Me, and (CF₃)(MeO)C:C(CF₃).CO₂Me. The influence of allylic chlorine and of reaction time on the formation of these products, and mechanistic pathways for their formation are considered.     

Selective aerobic oxidation of allylic and benzylic alcohols catalyzed by N-hydroxyindole and copper(I) chloride

In the presence of copper(I) chloride, tert-butyl 1-hydroxy-2-methyl-6-trifluoromethyl-1H-indole-3-carboxylate acted as a catalyst for the chemoselective aerobic oxidation of allylic and benzylic alcohols. A variety of primary and secondary allylic and benzylic alcohols were oxidized into the corresponding α,β-unsaturated carbonyl compounds in good yields without affecting non-allylic alcohols.     

Controlled introduction of allylic group to chlorosilanes

Allylation of chlorosilanes has been achieved with allylsamarium bromide, especially in a controlled manner. Thus allylation of trisubstituted chlorosilanes (R₃SiCl) afforded a variety of aryl, aralkyl, and alkenyl substituted allylsilanes. Dichlorosilanes (R₂SiCl₂) can either afford monoallylated silanes or diallylated silanes depending on the amount of allylsamarium bromide used. Similarly, trichlorosilanes (RSiCl₃) can selectively afford mono-, di-, and tri-allylation products. Finally, perchlorosilane (SiCl₄) was allylated stepwise and the corresponding silanes containing one, two, three or four allylic groups, respectively, were obtained in satisfactory yields.