Prins cyclizations in silyl additives with suppression of epimerization: versatile tool in the synthesis of the tetrahydropyran backbone of natural products.

[reactions: see text] A catalytic Prins cyclization reaction has been developed. The involvement of trimethylsilyl halides offers a versatile route to the formation of cis-4-halo-2,6-disubstituted tetrahydropyran rings. The problem of epimerization in Prins cyclization has also been addressed in the total synthesis of (-)-centrolobine using this methodology.

Enantioselective allylation of ketones catalyzed by chiral In(III)-PYBOX complexes.

In the presence of 20 mol% of chiral catalytic complex prepared from In(OTf)3 and chiral PYBOX, allyltributylstannane reacted with achiral ketones to afford the corresponding homoallylic alcohols in moderate to high enantioselectivities (54-95% ee), which constitutes the first example of enantioselective allylation of ketones catalyzed by the chiral In(III)-PYBOX complex.

Gram-scale synthesis of (-)-epibatidine.

[reaction: see text] A gram-scale approach toward (-)-epibatidine (1, naturally occurring enantiomer), a novel class of amphibian alkaloid, has been developed from readily available starting materials using mild and easily controlled reactions. The entire synthetic route is straightforward and convenient for gram-scale synthesis.

Catalytic enantioselective allylation of ketones via a chiral indium(III) complex.

[reaction: see text] A chiral indium complex has been discovered to effect high enantioselectivities in the addition of allyltributylstannanes to ketones. The allylation of a variety of aromatic, alpha,beta-unsaturated and aliphatic ketones resulted in good yields and high enantioselectivities (up to 92% ee).

Catalytic enantioselective Diels-Alder reaction via a chiral indium(III) complex.

[reaction: see text] A chiral indium complex has been developed to effect high enantioselectivities in catalyzing enantioselective Diels-Alder reaction. The cycloaddition of a variety of cyclic and open-chained dienes to 2-methacrolein and 2-bromoacrolein resulted in good yields and excellent enantioselectivities (up to 98% ee).

Enantioselective allylation of aldehydes catalyzed by chiral indium(III) complexes immobilized in ionic liquids.

In the presence of chiral catalytic complexes prepared from In(OTf)3 and chiral PYBOX ligands, allytributylstannane reacted with aldehydes in ionic liquids to afford the corresponding homoallylic alcohols in high enantioselectivities (86-94% ee) and good yields (68-89%); the chiral catalysts immobilized in ionic liquids could be reused with comparable enantioselectivities and yields.

Catalytic asymmetric allylation of aldehydes via a chiral indium(III) complex.

A chiral indium complex has been discovered to effect high enantioselectivities in the addition of allyltributyl stannanes to aldehydes. The allylation of a variety of aromatic, alpha,beta-unsaturated and aliphatic aldehydes resulted in good yields and high enantioselectivities (90-96% ee).

Enantioselective synthesis of homoallylic alcohols via a chiral In(III)-PYBOX complex.

In the presence of 20 mol% of a chiral catalytic complex prepared from In(OTf)(3) and chiral PYBOX, allyltributylstannane reacted with aldehydes to afford the corresponding homoallylic alcohols in moderate to high enantioselectivities (60-93% ee).

Highly enantioselective allylation of aldehydes catalyzed by indium(III)-PYBOX complex.

A chiral indium(III)-PYBOX complex prepared from indium triflate and chiral PYBOX has been discovered to effect high enantioselectivities in the addition of allyltributyl stannane to aldehydes. The allylation of a variety of aromatic, alpha,beta-unsaturated, and aliphatic aldehydes resulted in good yields and high enantioselectivities (up to 94% ee).

Synthetic studies towards anti-SARS agents: application of an indium-mediated allylation of α-aminoaldehydes as the key step towards an intermediate.

was identified as a good starting point for modification, leading to an efficient and bio-available inhibitor for the SARS coronavirus main proteinase (SARS-CoV M). Synthesis of intermediate and analogues proceeded via a highly diastereoselective indium-mediated allylation of α-aminoaldehydes.

Silicon-assisted propargylic transfer to aldehydes.

A new and efficient method of obtaining homopropargylic alcohols via homopropargylic transfer from the allenic alcohol to various aldehydes in the presence of Lewis acid catalysts is described; stereochemical studies have shown that this process is the first oxonium [3,3]-sigmatropic rearrangement of an allenic alcohol to a homopropargylic alcohol in the presence of aldehydes and Lewis acid.

Asymmetric synthesis of C-aliphatic homoallylic amines and biologically important cyclohexenylamine analogues.

An efficient method for the asymmetric synthesis of C-aliphatic homoallylic amines with up to 94% yield and 80% de is reported. Ring-closing metathesis of several chiral homoallylic amines using the second-generation Grubbs catalyst provided easy access to a wide variety of cyclohexenylamines.

Highly efficient chemical kinetic resolution of bishomoallylic alcohols: synthesis of (R)-sulcatol.

[reaction: see text] A highly efficient chemical kinetic resolution of bishomoallylic alcohols was developed when the alcohols underwent In(OTf)(3)-catalyzed 3,5-oxonium-ene-type cyclization with steroidal aldehyde 2. Consistently high enantiomeric excess (up to >99%) was obtained.

An unusual approach to the synthesis of enantiomerically cis linear homoallylic alcohols based on the steric interaction mechanism of camphor scaffold.

Camphor is used as the chiral auxiliary for the enantioselective synthesis of cis linear homoallylic alcohols. A range of catalysts, aldehydes, and solvents were investigated to obtain the optimum yield, enantioselectivity, and cis olefinic geometry. [structure: see text]

Indium-mediated reaction of trialkylsilyl propargyl bromide with aldehydes: highly regioselective synthesis of allenic and homopropargylic alcohols.

High regioselective preparation of either the allenic alcohols or homopropargylic alcohols using the indium-mediated reaction of trialkylsilyl propargyl bromides with various aldehydes has been accomplished. By just changing the silyl groups and the reaction conditions, both the allenic and homopropargylic alcohols can be obtained in high regioselectivities.

A novel and general alpha-regioselective and highly enantioselective prenylation of aldehydes.

This communication describes a novel and general method for the alpha-regioselective prenylation of carbonyl compounds. This method which employs chiral gamma-prenyl-1,5 diol as the prenyl source using a catalytic amount of Lewis or Brønsted acid affords the products in excellent enantioselectivies (up to 98% ee) and good yields (up to 95% yield). Furthermore, the reaction is highly chemoselective, reacting selectively with the aldehyde without affecting the enone and the alpha,beta-unsaturated ester functionalities.

Development of a highly alpha-regioselective metal-mediated allylation reaction in aqueous media: new mechanistic proposal for the origin of alpha-homoallylic alcohols.

This paper described a general method to obtain alpha-adduct homoallylic alcohols using indium, zinc, and tin in water. A new mechanism was proposed to account for the formation of these synthetically difficult-to-obtain molecules. Generally, this method can be performed with a wide range of aldehydes and allylic halides with just 6 equiv of water added, giving the alpha-adduct in high selectivities.

InCl(3)-catalyzed three-component asymmetric Mannich-type reaction in methanol.

[reaction: see text] A one-pot InCl(3)-catalyzed Mannich-type reaction was carried out in methanol. High diastereoselectivities and high yields were obtained. In addition, after the reaction was completed, InCl(3) can be recycled and reused without a drop of activity and selectivity.

The first example of enantioselective allyl transfer from a linear homoallylic alcohol to an aldehyde.

[reaction: see text] The first example of enantioselective linear homoallylic alcohol transfer reaction was revealed. In all cases, the whole rearrangement is thermodynamically favorable and a steric effect is the driving force of this reaction. The preservation of the stereocenter and olefin geometry together with the isolation of gamma-adduct homoallylic alcohols in one isomeric form have warranted the proposed mechanism.

Nickel-catalyzed homoallylation reaction of aldehydes with 1,3-dienes: stereochemical and mechanistic studies.

[reaction: see text] Contrary to what was reported, the coupling reaction of nickel-catalyzed cyclic diene such as cyclohexadiene with carbonyl compounds in the presence of diethyl zinc afforded gamma,delta-alkenyl alcohols in good yields.

Stereocontrolled synthesis of linear 22R-homoallylic sterols via a triflic acid-catalyzed 2-oxonia Cope rearrangement.

[reaction: see text] Poor stereoselectivity caused by the involvement of side reaction pathways was observed in the In(OTf)(3)-catalyzed allyl-transfer reaction (R = electron-withdrawing group). Subsequently, it was found that the employment of triflic acid (TFA) as catalyst could successfully suppress the side reaction pathways and, hence, achieve high stereoselectivity.

The First In(OTf) -Catalyzed Conversion of Kinetically Formed Homoallylic Alcohols into the Thermodynamically Preferred Regioisomers: Application to the Synthesis of 22α-Sterols.

A retro-ene reaction that generates the parent aldehyde and a sigmatropic rearrangement are involved in the In(OTf) -catalyzed conversion of homoallylic alcohols 1 into the thermodynamically favored regioisomers 2. This method can be used for the stereocontrolled synthesis of linear homoallylic 22α-sterols from their readily accessible branched 22β isomers.