Enantioselective synthesis of C2-symmetric diols

Chiral 1,3,2-oxazaborolidines in asymmetric synthesis: recent advances

“…It is known that the non-catalytic reduction of dicarbonyl compounds by borane yields diols in the meso-form. 97 In the catalytic reduction of diphenyl diketones 67 (R 1 = Ph) (10 mol.% of the catalyst 51), the meso : R,R (or S,S) ratio varies from 48 : 52 (n = 1) to 21 : 79 (n = 2), 9 : 91 (n = 3) or 2 : 98 (n = 4). 112 ± 114 O R Ar R = CH2Cl, 82,90 CH2Br, 90,93,94 CH2OTHP (THP is tetrahydropyranyl), 95 CH2N3 (ee 91% ± 100%), 96 (CH2)nC(O)R (R = Me, Bu t , Ph; n = 0 ± 4, both carbonyl groups are reduced simultaneously), 97 CH2SO2Ar, 98 (CH2)nP(O)(OPr i )2 (n = 1, 2), 86,99 CF3, 57, 84 CCl3; 28,84,88 Ar = Ph, m(p)-R H C6H4 (R H = Alk, Hal), 100 ± 103 After crystallisation of the diol 68, ee of the S,S-enantiomer was 99% (the content of the meso-form was < 1%).…”

Syntheses and applications of C2-symmetric chiral diols

“…2 However, oxazaborolidine-catalyzed reductions override this preference yielding chiral 1 as the major product with moderate enantioselectivity (Scheme 1). 3 Our group established an efficient oxazaborolidine-catalyzed enantioselective route to enantiomerically pure (S,S)-hydrobenzoins. 4 Chiral products were obtained with high stereochemical control (Scheme 2).…”

Organocatalytic Asymmetric Atroposelective Construction of Axially Chiral 1,4-Distyrene 2,3-Naphthalene Diols

“…3 The chiral diols commonly used as catalysts or ligands are C 2 -symmetric diols that bear two hydroxyl groups in a tunable dihedral angle to meet the coordination requirements and one rigid C 2 -symmetric axis to play a fundamental cooperative role in the stereochemical control (Scheme 1a). 4 To our knowledge, chiral diols bearing two hydroxyl groups in a single plane (no angle) along with two chiral axes remain largely unaddressed, probably due to a lack of reliable synthetic routes to atroposelectively construct two contiguous enantioenriched chiral axes. Therefore, it is necessary to develop a synthetic approach to construct two chiral axes surrounding the diols to afford novel axial chirality compounds.…”