Isabelle Beaudet

Regio- and Stereocontrolled Stannylmetallation of 3,3-diethoxy-prop-1-yne and 4,4-diethoxy-but-1-yne : An efficient access to the corresponding vinyltins with fixed configurations

Abstract Stannylmetallation of propargyl or homopropargyl acetals has been exploited to obtain the corresponding vinyltin as a single geometrical isomer, result of a cis-addition on the triple bond.

Preparation of γ-siloxyallyltributylstannanes and their use in the synthesis of (±)-1-deoxy-6,8a-di-epi-castanospermine

gamma-siloxyallyltributylstannanes were selectively obtained as E or Z isomers from beta-tributylstannylacrolein upon reaction with lithium or magnesium alkylcyanocuprates. The ability of the reagents to give a high syn selectivity when added to iminium salts has been used for the efficient synthesis of (+/-)-1-deoxy-6,8a-di-epi-castanospermine from succinimide. The key step of the synthesis was the allylstannation of the N-allyliminium intermediate followed by ring closing metathesis.

A convenient synthesis of protected e-enynals via cross coupling of vinyltin acetals with bromoalkynes

Abstract E-conjugated enynes bearing an acetal function on the allylic or the homoallylic position or/and on the propargylic or the homopropargylic position were conveniently obtained at a room temperature in DMF via cross coupling of the corresponding vyniltins with 1-bromoalk-1-ynes in the presence of PdII catalysts.

Electrochemical Cleavage of Sulfonamides: An Efficient and Tunable Strategy to Prevent β-Fragmentation and Epimerization

The electrochemical reduction of sensitive sulfonamides is described. The addition of a benzoyl group on the nitrogen atom facilitates the reductive cleavage of sulfonamides preventing β-fragmentation and epimerization. This strategy was successfully applied to the cyclopropylamine and to α-amino stannanes.

E- and Z-β-formylvinyl synthons from 1-tributylstannyl-3,3-diethoxy-prop-1-ene via cross coupling with acid chlorides

The easily prepared and stored E-1-tributylstannyl-3,3-diethoxy-prop-1-ene 1E reacts with acyl chlorides in DMF in the presence of PdCl2(MeCN)2 to give the expected 1,4-ketoacetals (E isomers). Similarly cross coupling of 1E with tosyl chloride performed in THF in the presence of Pd(PPh3)4 affords the E-β-diethoxymethylvinylsulphone whose metallation with MeLi, LiBr generates a β-formylvinylanion equivalent with the anionic centre in a cis relationship relative to the diethoxymethyl group.

Stereodivergent synthesis of iminosugars from stannylated derivatives of (S)-vinylglycinol.

An original access to iminosugars from a cis/trans mixture of stannylated oxazolidinones 5 is reported. The dehydropiperidines 7-trans and 7-cis were obtained stereoselectively with an RS and SS configuration depending on the order of the Sn-Li transmetalation (followed by electrophilic trapping) and of the ring closing metathesis reactions due to the stereoselective epimerization of the α-aminoanion intermediate. The dehydropiperidines 7-trans and 7-cis were subsequently used for the synthesis of enantiopure homonojirimycin analogs.

Reactivity of γ-benzyloxyallyltins with cyclohexylidene glyceraldehydes

Abstract Benzyloxyallyltributyltins were obtained in 50–80% yield by S N 2′ reaction of alkyl-cyanocuprates with 3,3-dibenzyloxy-1-tributylstannylprop-1-ene in the presence of boron trifluoride. They reacted with cyclohexylidene glyceraldehyde in the presence of different Lewis acids and the obtained diastereomeric adducts were unambiguously identified after an ozonolysis/deprotection sequence by comparison with authentic aldopentoses. The mechanisms are briefly discussed as well as the relationship of the configuration of the reagents to the selectivity of the allylstannation reaction.

Synthesis of Highly Enantioenriched Chiral α-Aminoorganotins via Diastereoselective Ring Opening of Chiral N-(Arenesulfonyl) 2-Tributylstannyloxazolidines

trans-N-(Arenesulfonyl)-2-tributylstannyloxazolidines derived from (R)-phenylglycinol were diastereoselectively ring-opened by soft organometallic reagents in the presence of BF(3).OEt(2). Both higher order organocuprates and allyltributyltin afforded the desired products in good-to-excellent yields and high diastereoselectivities (dr up to 99/1). The stereochemical assignments of tributylstannyl-beta-aminoalcohols were firmly established from NMR data and after determination of several radiocrystallographic structures. Mechanisms were proposed in order to rationalize the observed selectivities.

Substitution of the acetoxy groups of dialkoxymethylacetates by organometallic reagents: a route to allyl-, propargyl-, homoallyl-, homopropargyl- and α-stannylacetals

Abstract The substitution of the acetoxy groups of dialkoxymethylacetates by organometallic reagents has been examined in a search for new methods of preparing functional acetals. The efficiency of the substitution of the acetoxy group is highly dependent on the nature of the organometallic reagents: soft nucleophiles with strong electrophilic assistance by the counterion are the best reagents. Allyl-, propargyl-, homoallyl-, homopropargyl- and α-stannylacetals have been made by this route, in which dialkoxymethylacetates often function as useful substitutes for dialkylphenylorthoformates.

Preparation of enantiomerically enriched α‐aminoorganostannanes and their applications in stereoselective synthesis

This review deals with the preparation of chiral, nonracemic α-aminoorganostannanes and their applications in asymmetric synthesis. The pioneering works in this field date back almost 20 years ago and since then extensive research has been carried out to develop efficient and selective routes to highly enantioenriched α-aminoorganostannanes. The facile Sn/Li transmetalation of these compounds by n-BuLi has led to various applications in stereoselective synthesis. Selected examples using chiral α-aminoorganostannanes as starting materials will be reported.