Enzyme-promoted desymmetrization of bis(2-hydroxymethylphenyl) sulfoxide as a route to tridentate chiral catalysts

Enzymatic Synthesis of Enantiopure Precursors of Chiral Bidentate and Tridentate Phosphorus Catalysts

“…Thus, we have recently succeeded in the chemoenzymatic synthesis of a variety of tridentate ligands 3, containing a stereogenic sulfinyl moiety, an enantiomeric amine fragment and the hydroxy group (Scheme 1). [2] The crucial step was the enzyme-promoted desymmetrization of the prochiral sulfoxide 1, which allowed us to obtain the desired precursor 2 in one step in high yield and in an almost enantiomerically pure form. The ligands 3 proved to be excellent catalysts for the asymmetric organozinc additions to aldehydes, [3,4] Michael additions to enones [5] and in the nitroaldol (Henry) reaction.…”

Desymmetrization of Prochiral Diaryl Sulfoxides by an Asymmetric Sulfoxide–Magnesium Exchange

“…[15] Figure 1 depicts selected prochiral monosulfoxides, in which the sulfur atom became a stereocenter through enzymatic monofunctionalizations of one of the two side-chain functional groups. [16][17][18][19][20] Recently we desymmetrized the prochiral dibromo alcohol 5 by an asymmetric bromine-magnesium exchange [21] (Scheme 1; ! 6 + iPrBr).…”

“…6 + iPrBr). [22] Theorizing about the underlying mechanism we wondered whether a similar reaction de- Representative substrates for enzymatic desymmetrizations by acetylation of 1, [16] nitrile hydrolysis of 2, [17] and ester hydrolyses of 3 [18] and 4. [19,20] Scheme 1.…”

N-Trityl-aziridinyl alcohols as highly efficient chiral catalysts in asymmetric additions of organozinc species to aldehydes

“…Among chiral amine alcohols, aziridine alcohols constitute as a very interesting class of compounds when applied as chiral ligands especially in the asymmetric additions of organozinc species to carbonyl compounds. [6][7][8][9][10] In continuation of our current interests in the field of asymmetric synthesis, 11,12 especially in the application of aziridine-based chiral catalysts [13][14][15][16][17][18][19][20][21] and taking into account the fact that aziridines strongly coordinate to organozinc species, [22][23][24] we focused our attention on the synthesis of various N-trityl-aziridinyl alcohols and checked their catalytic activity toward the addition of diethylzinc and phenylethynylzinc to aldehydes. According to previous literature reports, such types of chiral catalysts have been tested in model asymmetric additions of diethylzinc to aldehydes to give the corresponding chiral alcohols in high chemical yield (around 90%) and with high enantiomeric excess values (up to 98%).…”