Yannick Vallée

Murielle Chavarot; Janice J. Byrne; Pierre Y. Chavant; Yannick Vallée

Abstract The new chiral heterobimetallic complex Sc(BINOL) 2 Li 1 was prepared and used as a catalyst in the enantioselective addition of a cyanide source (HCN or TMSCN) to several imines. High conversion rates and enantiomeric excesses (e.e.s) as high as 95% were obtained.

Janice J. Byrne; Murielle Chavarot; Pierre-Yves Chavant; Yannick Vallée

Abstract The asymmetric addition of TMSCN to a ketimine has been achieved by use of catalytic quantities of chiral titanium(IV) complexes. Fast conversions together with enantiomeric excesses as high as 59% have been achieved.

Hélène Chalaye-Mauger; Jean-Noel Denis; Marie-Thérèse Averbuch-Pouchot; Yannick Vallée

Abstract The reaction of nitrones with various indole derivatives has been studied. When the reaction was promoted by ClSiMe3, the isolated products were 3,3′-diindolylalkanes. With HCl as the activating reagent, 3-indolylhydroxylamines were isolated. The diastereoselectivity of this condensation with a nitrone derived from cysteine was investigated. A method for the introduction of an alkylhydroxylamino group onto position 2 of indole, the synthesis of three natural 3,3′-diindolylalkanes and of non-symmetric diindolylalkanes are also reported.

Jean-Noel Denis; Hélène Mauger; Yannick Vallée

Abstract The reaction of nitrones with indoles in the presence of HCl gives indolyl N -hydroxylamines. In the presence of Me 3 SiCl symmetrical diindolylalcanes are obtained. A synthesis of asymmetrical diindolylalcanes and the syntheses of three natural symmetrical diindolylalcanes are reported.

Jean-Noẽl Denis; Sylvie Tchertchian; Axel Tomassini; Yannick Vallée

Abstract Nitrones react with the lithium anions of ethyl and t-butyl propiolates to give acetylenic N-hydroxylamines. The reduction of these compounds with Zn in the presence of an acid leads to E and Z α,β-ethylenic-γ-aminoacids derivatives. The stereoselectivity of these reactions was studied.

Pierre Beslin; Patrick Metzner; Yannick Vallée; Jean Vialle

Abstract Deprotonation of dithiopropanoates with LDA in THF solution at −78°C afforded chiefly the cis lithium thioenolate in contrast with the trans enolization of most of carbonyl compounds. The cis geometry was proved by a thio-Claisen rearrangement.

Samir K. Patel; Sandrine Py; Shashi U. Pandya; Pierre Y. Chavant; Yannick Vallée

Abstract 1,3-Asymmetric induction in the Et2Zn-catalyzed addition of terminal alkynes was studied with nitrones bearing a chiral auxiliary on their nitrogen atom. The obtained propargylic N-hydroxylamines were generally isolated in good yields and with satisfactory to excellent diastereoselectivities.

Stephanie Desvergnes; Yannick Vallée; Sandrine Py

A general method to prepare a new class of carbohydrate-derived, enantiomerically pure polyhydroxypyrroline N-oxides from their alkoxy (protected) derivatives is presented. Boron trichloride is shown to cleave efficiently benzyl ethers and ketals without affecting the imine N-oxide functionality of nitrones. The same reagent (BCl3) also allowed the efficient synthesis of a polyhydroxylated N-hydroxypyrrolidine, giving access to a novel class of N-hydroxyiminosugars.

Murielle Chavarot; Janice J. Byrne; Pierre Y. Chavant; Josephine Pardillos-Guindet; Yannick Vallée

Abstract Addition of conformationally flexible biphenols to ( R )-BINOL–Ti(O i Pr) 2 , forms a new catalytic species with which ee s are as high as 97.3% in the hetero-ene reaction of n -butyl glyoxylate to α-methyl styrene.

Pavandeep S. Aujla; Charlotte P. Baird; Paul C. Taylor; Hélène Mauger; Yannick Vallée

Abstract Reaction of chloramine-T and methyl p-tolyl sulfide to give the corresponding sulfimide appears to proceed via a nitrene transfer mechanism in the presence of a copper(I) catalyst and a second nitrogen ligand .