Ti-exchanged ZSM-5 as heterogeneous catalyst for allylation of aldehydes with allyltributylstannane

Titanium exchanged ZSM-5 catalyst has been prepared by treating an aqueous solution of titanium (IV) chloride with ZSM-5. The supported catalyst has been explored as effective and reusable catalyst for allylation reaction of aldehydes with allyltributylstannane. The new catalytic system promotes efficiently the allylation reaction in toluene condition to produce homoallylic alcohols in high yield.     

Formation of homoallylic bromohydrins in indium-mediated allylation reactions of phenacyl bromides in aqueous solution

A method is described for carrying out indium-mediated allylation reactions of phenacyl bromides in aqueous solution that form homoallylic bromohydrins. By employing subsequent base treatment, the homoallylic bromohydrins were converted to allylic epoxides. Finally, the process has been used as a key step in a concise sequence for the synthesis of 3-allylbenzofuran.     

Chemoselective allylation of aldehydes using cerium(III) chloride: simple synthesis of homoallylic alcohols

Aldehydes undergo smooth nucleophilic addition with allyltributylstannane in the presence of CeCl₃·7H₂O in acetonitrile under extremely mild reaction conditions to afford the corresponding homoallylic alcohols in excellent yields with high chemoselectivity. This method is very useful especially for the allylation of aldehydes bearing acid sensitive functionalities such as TBDMS, THP ethers, acetonides, aryl alkyl ethers and carbamates.     

A convenient synthesis of substituted 3-bromotetrahydrofurans from homoallylic alcohols

Substituted 3-bromotetrahydrofurans were prepared from homoallylic alcohols via bromination and cyclization in methanol in the presence of potassium carbonate.     

Gadolinium(III) chloride: a novel and an efficient reagent for the synthesis of homoallylic alcohols

Carbonyl compounds efficiently undergo nucleophilic addition reactions with allylstannanes in the presence of GdCl₃·6H₂O in acetonitrile under extremely mild reaction conditions to give the corresponding homoallylic alcohols in excellent yields and with high chemoselectivity.     

Scandium-catalyzed allylboration of aldehydes as a practical method for highly diastereo- and enantioselective construction of homoallylic alcohols

A general approach for the allylation of aldehydes using stable, air-tolerant camphor-based chiral allylboronates under Sc(OTf)3 catalysis is described. This practical methodology provides both syn and anti propionate units and other homoallylic alcohols with very high levels of diastereo- and enantioselectivity for several substrates, including functionalized aliphatic aldehydes useful toward the elaboration of complex natural products.     

Indium-mediated allylation of aryl trichloromethyl ketones in aqueous media

It is described that indium-mediated allylation of trichloromethyl ketones could afford the corresponding homoallylic alcohols smoothly in aqueous media.     

Chiral phosphine oxide BINAPO as a catalyst for enantioselective allylation of aldehydes with allyltrichlorosilanes

The effectiveness of chiral phosphine oxide BINAPO as a catalyst for the enantioselective addition of allyltrichlorosilanes to aldehydes was demonstrated, wherein the combination of diisopropylethylamine and tetrabutylammonium iodide as additives is crucial for accelerating the catalytic cycle.     

Indium-mediated asymmetric Barbier-type allylation of aldimines in alcoholic solvents: synthesis of optically active homoallylic amines

[reaction: see text] Chiral aldimines derived from phenylglycinol were diastereoselectively allylated with indium powder/allyl bromide in alcoholic solvents. Both aliphatic and aromatic aldimines provided good yield of the desired products with high diastereoselectivity. A racemization-free protocol for removal of the phenylglycinol auxiliary was also developed. The stereochemical assignment of the homoallylic amine was made by NMR spectroscopy and a transition state model was proposed to explain the selectivity.     

A highly enantioselective one-pot synthesis of homoallylic alcohols via tandem asymmetric allyl transfer/olefin cross metathesis

A highly enantioselective one-pot synthesis of linear homoallylic alcohols with terminal ester functionality has been achieved. The reactions were controlled by ordered addition of reagents and catalysts, ensuring complete consumption of aldehyde. The synthetic utility of this strategy has been demonstrated in a short synthesis of a low boiling point intermediate for grahamimycin A.     

Efficient synthesis of homoallylic alcohols and amines using 2,4,6-trichloro-1,3,5-triazine

The allylation of aldehydes and imines has efficiently been carried out by treatment with allyltributylstannane in the presence of a catalytic amount of 2,4,6-trichloro-1,3,5-triazine at room temperature to form the corresponding homoallylic alcohols and amines, respectively, in high yields.     

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.     

An efficient Bi/NH4I-mediated addition reaction for the highly diastereoselective synthesis of homoallylic alcohols in aqueous media

An efficient water-based bismuth-mediated addition reaction of carbonyl compound with cyclic allylic halide was developed.The reactions proceeded smoothly in aqueous DMF in the presence of ammonium iodide to afford the corresponding syn-homoallylic alcohols in moderate to good yields with excellent diastereoselectivities(>99:1 syn:anti).Reversal of product diastereoselectivity was observed when heteroaryl aldehyde possessing an adjacent chelating nitrogen atom was employed as substrate.     

Catalytic asymmetric allylation of aldehydes using the chiral (salen)chromium(III) complexes

The enantioselective addition of allylstannanes to glyoxylates and glyoxals, as well as simple aromatic and aliphatic aldehydes, catalyzed by chiral (salen)Cr(III) complexes, has been studied. The reaction proceeded smoothly for the reactive 2-oxoaldehydes and allyltributyltin in the presence of small amounts (1-2 mol %) of (salen)Cr(III)BF₄ (1b) under mild, undemanding conditions. However, in the case of other simple aldehydes, the use of high-pressure conditions is required to obtain good yields. Classic chromium catalyst 1b, easily prepared from the commercially available chloride complex 1a, affords homoallylic alcohols usually in good yield and with enantiomeric purity of 50-79% ee. The stereochemical results are rationalized on the basis of the proposed model.     

Ring-closing metathesis as a tool for the efficient preparation of chiral spirocyclic ethers from homoallylic alcohols

The preparation of chiral spirocyclic ethers via allylic etherification/olefin metathesis of homoallylic alcohols is investigated. This reaction sequence transforms the enantiopure substrate alcohols, synthesized by a one-pot asymmetric rhodium-catalyzed conjugate addition/metal-mediated allylation procedure, into the desired spiro ethers with full conversions and in excellent isolated yields. The synthetic sequence provides an efficient means for a rapid construction of functionalized spiro ethers in a stereoselective manner.     

Indium-mediated allylation/propargylation of α-diazoketones: a facile synthesis of 1-bromo-2-alkyl- or 2-arylpent-4-en-2-ols

α-Diazoketones undergo smooth allylation with successive bromide insertion with allylindium bromide generated in situ from allyl bromide and indium metal to produce 1-bromo-2-alkyl- or 2-arylpent-4-en-2-ols in high yields. Addition of propargylindium bromide produces 1-bromo-2-alkyl-or 2-arylpent-4-yn-2-ols under similar conditions.     

Regio- and stereochemical aspects in the synthesis of homoallylic alcohols from benzoins and their iodocyclisation to 2,3-diphenyltetrahydrofurans

Indium mediated allylation, crotylation and cinnamylation of benzoins and its substituted derivatives in THF-H₂O (2/1) provide a range of homoallylic alcohols. In general, the benzoins undergo allylation and crotylation in a sluggish manner compared to those observed earlier in the case of α-hydroxy aldehydes and are significantly affected by the electronic features of both the benzoin and indium organometallic reagent. The reactions exhibit higher order of diastereoselectivities than those observed for α-hydroxy aldehydes. The cinnamylation though proceeds in a highly diastereoselective manner but is restricted to only benzoin and 4,4′-dichlorobenzoin. The homoallylic alcohols undergo I₂ mediated intramolecular diastereoselective cyclization to provide 2,3-diphenyltetrahydrofuran derivatives. The relative stereochemistries in tetrahydrofurans and homoallylic alcohols have been assigned by coupling constants, NOE experiments and in one case by X-ray crystallography.     

Asymmetric allylation. An effective strategy for the convergent synthesis of highly functionalized homoallylic alcohols

A survey of stereoselective syntheses of highly-functionalized homoallylic alcohols is described via asymmetric allylation. Initial transmetalation from an allylic stannane to a C-2 symmetric chiral borane controller is followed by low temperature addition to aldehydes efficiently effecting convergent strategies to complex targets.     

A convenient procedure for bismuth-mediated Barbier-type allylation of aldehydes in water containing fluoride ions

A new and convenient procedure for synthesis of homoallylic alcohols in generally good to excellent yields has been developed. The bismuth-mediated Barbier-type allylation of aldehydes (aromatic, aliphatic, alicyclic and heterocyclic) with allyl bromide has been carried out smoothly in water in the presence of fluoride ions.     

Diastereoselective synthesis of enantioenriched homopropargyl amino alcohols from α-dibenzylamino aldehydes and their use as chiral synthons

Homochiral α-dibenzylamino aldehydes, prepared from the corresponding α-amino acids, react with propargyl bromide and zinc in DMF/THF (1:1) or DMF/Et₂O (1:1) at 20 °C to afford, in good yields and dr, homopropargylic 1,2-amino alcohols. anti Diastereomers were always formed as major products in this reaction. These compounds are versatile intermediates for a variety of synthetic targets: γ-amino-β-hydroxy-ketones, 4-amino-1,3-diols, 1,7-diamino-2,6-diols, and ω-amino-δ-hydroxy esters.