Novel Approach to the Synthesis of Enantioenriched Sulfoxides. Highly Diastereoselective Alkylation of Sulfenate Anions with 1,4-Asymmetric Induction

Abstract

[reaction: see text] Efficient 1,4-asymmetric induction with an enantiopure aminoalkyl group as the chiral auxiliary has been achieved in the first example of diastereoselective alkylation (up to 98:2) of a sulfenate anion, readily prepared by oxidation of the corresponding thiolate. The stereochemistry of the sulfoxide produced is the opposite of that obtained by the conventional route based on oxidation of the sulfide precursor.

Application of N,S-chelating chiral ligands and zinc complexes in catalytic asymmetric hydrosilylation using polymethylhydrosiloxane

“…This air-stable zinc complex, obtained by this one pot procedure, has been fully characterised by all spectroscopic methods. 14 The enantiopure thiophenol 2 could be prepared from 1-(R)-phenylethylamine following the methodology of van Koten and co-workers, 10 recently modified by Perrio and co-workers, 11 that is, selective ortho-lithiation of (S)-methylbenzyldimethylamine, trapping of the intermediate with elemental sulfur, acidic work-up and purification by sublimation gave the dimethylamino thiol 2 in only moderate yield. The chiral disulfide 3 could be prepared according to the procedure developed by Braga et al starting from (L L)-cysteine.…”

“…In view of the promising results obtained by van Koten and co-workers with amino thiol 2 for the enantioselective addition of dialkylzincs to aldehydes, 10 which have been recently developed by Perrio and co-workers in the diastereoselective alkylation of sulfenate anions, 11 we became interested by its evaluation in our hydrosilylation conditions. Disulfide 3 was also evaluated due to the result obtained by Braga et al in the asymmetric addition of diethylzinc to aldehydes.…”

A New Class of Organocatalysts: Sulfenate Anions

“…Single crystals suitable for a crystallographic study were obtained after addition of [18]crown-6 and layering with hexanes. Single crystals suitable for a crystallographic study were obtained after addition of [18]crown-6 and layering with hexanes.…”

“…Single crystals suitable for a crystallographic study were obtained after addition of [18]crown-6 and layering with hexanes. [18] A gasphase DFT calculation at the B3LYP/6-31G* level of theory was performed on the [PhS(O)CHPh] À anion and the corresponding neutral sulfoxide, PhS(O)CH 2 Ph (see the Supporting Information for details). The sp 2 nature of the benzylic carbon atom was evident from the short S À C bond of 1.691(2) , compared to the C À S bond length of 1.837(2) that was reported for the benzylic sulfoxide {2-[(NMe 2 )CHMe]C 6 H 4 }S(=O)CH 2 Ph.…”

“…To further characterize the catalyst resting state, we deprotonated benzyl phenyl sulfoxide (3 a) with KCH 2 Ph. Single crystals suitable for a crystallographic study were obtained after addition of [18]crown-6 and layering with hexanes. [17] The solid-state structure of the product, K([18]crown-6)(THF)[PhS(=O)CHPh], was determined to be monomeric with a potassium cation coordinated to both the a-carbon and oxygen atoms of the anion (Figure 2).…”