Novel C2-symmetric chiral ligands: enantioselective transformation of cyclic 1,2-diols into 1,2-bis(phenylsulfenyl) and 1,2-bis(phenylselenyl) derivatives

Chiral C2-symmetric S,S- and Se,Se-donating ligands as well as the C1 mixed S,Se-donating ligands were prepared from optically active 1,2-cyclohexanediol and 1,2-cyclopentanediol via the respective SN2 reactions. The bis(chalcogen) ligands obtained effectively catalyze the asymmetric allylic alkylation with enantioselectivities of up to 50% ee.

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(+)-(1S,2S)-1,2-Bis(phenylsulfenyl)cyclohexaneC18H20S2De >98% (by 1H NMR)[α]D20=+120.0 (c 2.20, CH2Cl2) >95% eeSource of chirality: stereoselective nucleophilic substitutionAbsolute configuration: (1S,2S) (by chemical correlation)

(+)-(1S,2R)-2-PhenylselenylcyclopentanolC11H14OSeDe >98% (by 1H NMR)[α]D20=+49.3 (c 1.52, CH2Cl2) >95% eeSource of chirality: stereoselective nucleophilic substitutionAbsolute configuration: (1S,2R) (by chemical correlation)

(−)-(1R,2R)-1,2-Bis(phenylselenyl)cyclopentaneC17H18Se2De >98% (by 1H NMR)[α]D20=-18.0 (c 1.00, CH2Cl2) >95% eeSource of chirality: stereoselective nucleophilic substitutionAbsolute configuration: (1R,2R) (by chemical correlation)

(−)-(1R,2S)-2-PhenylselenylcyclohexanolC12H16OSeDe >98% (by 1H NMR)[α]D20=-8.3 (c 1.08, CH2Cl2) >95% eeSource of chirality: stereoselective nucleophilic substitutionAbsolute configuration: (1R,2S) (by chemical correlation)

(+)-(1S,2S)-1,2-Bis(phenylselenyl)cyclohexaneC18H20Se2De >98% (by 1H NMR)[α]D20=+90.8 (c 0.98, CH2Cl2) >95% eeSource of chirality: stereoselective nucleophilic substitutionAbsolute configuration: (1S,2S) (by chemical correlation)

(+)-(1S,2S)-1-Phenylsulfenyl-2-phenylselenylcyclohexaneC18H20SSeDe >98% (by 1H NMR)[α]D = +100.0 (c 0.91,CH2Cl2) >95% eeSource of chirality: stereoselective nucleophilic substitutionAbsolute configuration: (1S,2S) (by chemical correlation)

(−)-(1S,2R) O-Isopropyl-S-(2-hydroxycyclohexyl) dithiocarbonateC10H18O2S2De >98% (by 1H NMR)[α]D = −27.9 (c 1.02, CH2Cl2) >95% eeSource of chirality: stereoselective nucleophilic substitutionAbsolute configuration: (1S,2R) (by chemical correlation)