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.     

Stereochemically controlled synthesis of unsaturated 2,5-dialkyl furanes

The directing effect of a benzoate group in an acid-catalysed intramolecular nucleophilic opening over an epoxyalcohol benzoate is used in the enantioselective preparation of α,α'-dialkyl furanes     

Chemoenzymatic synthesis of optically active heterocyclic homoallylic and homopropargylic alcohols

A chemoenzymatic methodology has been developed using indium-mediated allylation of heterocyclic aldehydes under aqueous conditions followed by Pseudomonas cepacia lipase-catalyzed enantioselective acylation of racemic homoallylic and homopropargylic alcohols in organic media. It is observed that the lipase immobilized on ceramic particles (PS-C Amano II) catalyzes the resolution in a highly enantioselective manner in less time as compared to the native enzyme (PS Amano). The approach provides new functionalized chiral synthons useful in the synthesis of natural and pseudonatural products.     

Stereoselective synthesis of allylic sulfones via the oxonia-Cope rearrangement of homoallylic alcohols containing a homoallylic sulfone moiety

The homoallylic alcohols 3 that can be prepared by the indium-mediated addition of haloallylic sulfones 1 to aldehydes 2 undergo the oxonia-Cope rearrangement with aldehydes 2 to give rise to the allylic sulfones 4 containing a conjugated diene moiety in a highly stereoselective manner. Electron-rich aldehydes preferentially participate in this oxonia-Cope rearrangement with the homoallylic alcohols 3. Excellent correlations of the stereochemistry (anti-3 to trans-allylic sulfone 4 and syn-3 to cis-allylic sulfone 4) have been observed in the oxonia-Cope rearrangement.     

One-pot enantioselective synthesis of optically active homoallylic alcohols from allyl halides

A one-pot, convenient method for the preparation of optically active homoallylic alcohols from allyl halides was developed. Allyltrichlorosilanes were generated in situ from allyl halides and trichlorosilane in the presence of cuprous chloride and tertiary amine. Without isolation of the allyltrichlorosilanes, benzaldehyde and chiral biquinoline N,N'-dioxide were introduced into the same flask, producing the corresponding homoallylic alcohols with good to high enantioselectivities.     

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 new reaction: lead(IV) acetate-mediated oxidative fragmentation of homoallylic alcohols

Treatment of a homoallylic alcohol with lead(IV) acetate in refluxing benzene for 2 hours results in an oxidative cleavage to give a carbonyl compound and an allylic acetate with high yield.     

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.     

A new synthesis of sultams from amino alcohols

The base-mediated cyclization of N,O-dimesylate derivatives of cyclic and acyclic amino alcohols provides a simple access to five- and six-member sultams: isothiazolidine-1,1-dioxides and thiazinane-1,1-dioxides respectively.     

A versatile preparation of alpha,beta-unsaturated lactones from homoallylic alcohols

[formula: see text] A new method for the synthesis of alpha,beta-unsaturated lactones from beta-acetoxy aldehydes by reaction with the lithium enolate of methyl acetate was developed. The reaction is relatively insensitive to structural changes in the aldehyde substrates. The process was extended to the synthesis of five-ring lactones from alpha-acetoxy aldehydes. Experimental evidence regarding the mechanism of this one-pot transformation was obtained. The observations are consistent with a pathway involving an initial aldol condensation with subsequent acyl migration, lactonization, and beta-elimination and not an enolate equilibration-aldol mechanism.     

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.     

Stereochemically controlled synthesis of racemic sitophilate,the aggregational pheromone of the grain weevil

Controlled condensation of propionaldehyde with Li- or Si-enolates, generated from sec-amyl propionate, readily afforded a mixture of diasteromeric 2-methyl-3-hydroxypentanoic acid 3-pentyl esters, which were easily separated by chromatography. The erythro-isomer is the racemic form of the major component (sitophilate) of the aggregational pheromone of the grain weevil, a harmful granary pest. Beilis-Hillman condensation of propionaldehyde with sec-amyl acrylate under high pressure and subsequent hydrocuprination or hydrozirconation of the intermediate adduct afforded the (±)-sitophilate in an overall yield of >35%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 807–811, April, 1990.     

One-pot, three-component synthesis of linearly substituted homoallylic alcohols via allyl(isopropoxy)dimethylsilane

[reaction: see text] A two-step approach that involves the synthesis of vinylsilane from allyl(isopropoxy)dimethylsilane (6) and the subsequent Pd-catalyzed cross-coupling of the resulting vinylsilane is applied in developing a novel diversity-oriented, three-component synthesis to homoallylic alcohols of common structure 1. Upon treatment of 6 with s-BuLi, the silylallylmetal 5 is generated and reacted with carbonyl compounds to produce functionalized vinylsilanes, which can couple with aryl/vinyl halides in the presence of palladium catalyst to afford 1.     

Intramolecular anti-hydrosilylation and silicon-assisted cross-coupling: highly regio- and stereoselective synthesis of trisubstituted homoallylic alcohols

A highly regio- and stereoselective anti-intramolecular hydrosilylation of alkynyl silyl ethers catalyzed by a ruthenium arene complex has been developed. The resultant (Z)-alkylidenesilacyclopentanes are efficiently coupled with aryl or alkenyl halides in the presence of tetrabutylammonium fluoride and a palladium(0) catalyst. The yields are generally good, and the reaction is compatible with a wide range of functional groups. The overall transformation achieves the stereoselective conversion of homopropargyl alcohols to trisubstituted homoallylic alcohols. [reaction: see text]     

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.