Christophe Delas

Titanium-mediated intramolecular cyclization of tethered propargyl alcohol derivatives. Access to exocyclic bis-allenes and cyclobutene derivatives

Abstract Treatment of tethered bis-propargyl alcohol derivatives with (η 2 -propene)Ti(O- i -Pr) 2 afforded four- and five-membered rings bearing conjugated exocyclic bis-allenes. In the case of six- and seven-membered rings, bicyclic cyclobutenes were obtained in the same pot most likely via the intermediate bis-allenes.

Highly selective addition reaction of organotitaniums with Garner's aldehyde. Easy preparation of optically active allylic, allenylic, homoallylic and homopropargylic alcohols

Abstract Organotitanium complexes 3 – 5 prepared from a Ti(O- i -Pr) 4 /2/ i -PrMgX reagent ( 2 ) and the corresponding unsaturated compounds reacted with Garners aldehyde ( 1 ) to provide anti -addition products highly predominantly, thus allowing an easy access to a variety of optically active anti -1,2-aminoalcohol derivatives.

Asymmetric Mukaiyama aldol coupling between anti α-methyl-β-hydroxy enol silanes and propanal catalyzed by chiral binaphtholtitanium complex

Abstract In the presence of BINOL-Ti complex as a chiral promoter, the Mukaiyama aldol addition of racemic anti α-methyl-β-hydroxy enol silanes to propanal gives dihydroxy ketones bearing four stereocenters with good de and ee up to 50%. The major anti diastereoselectivity is in opposite to the syn diastereoselectivity obtained using TiCl4 and HO-protected enol silanes.

Site-selective mono-titanation of conjugated diynes with a Ti(II) alkoxide reagent. Concise preparation of stereo-defined enynes and dienynes

Conjugated diynes underwent selective mono-titanation with a Ti(II) reagent to give 1:1 diyne-titanium alkoxide complexes, which reacted with proton, aldehyde, and another acetylene to give stereo-defined enynes, enynols, and dienynes.

Use of chiral enolsilanes and chiral aldehydes in a Mukaiyama-type aldol reaction promoted by titanium(IV)isopropoxide

In the presence of a catalytic amount of titanium(IV) isopropoxide, an aldol reaction is conducted between chiral enolsilanes formed by an allyltitanation reaction and chiral aldehydes to afford ketones in high yields. These ketones were reduced and esterified by a Tischtschenko reaction to obtain esters bearing six or seven stereocenters.

Addition of chiral β-hydroxy (protected) enol silanes to benzaldehyde dimethyl acetal: Access to polypropionate five-carbon stereosequences

Abstract The title enol silanes react with benzaldehyde dimethyl acetal to give dihydroxy (protected) ketones with good to excellent de and enantiocontrol. Further DIBALH reduction affords stereoselectively (de=95%) polypropionate chirons.

Study of a tandem aldol–Tischtschenko reaction between chiral enolsilanes and aldehydes catalyzed by titanium(IV) isopropoxide

The synthesis and structure determination of polypropionate is presented. An allyltitanium complex is first used in an allyltitanation reaction; titanium(IV) isopropoxide is next utilized as catalyst in an aldol–Tischtschenko reaction. This method promotes the formation of esters bearing five or six stereocenters in two steps with a very high level of diastereoselectivity and very high yield.

Stereoselective one-pot preparation of 1,2,4,5-tetraalkylidene- and 1,4-dialkylidenecyclohexanes.

1,2,4,5-Tetraalkylidene- and 1,4-dialkylidenecyclohexanes were prepared by the regio- and stereoselective homocoupling of skip-type diynes and enynes, and their Diels-Alder reaction to form a polycyclic compound was demonstrated.