Stereospecific and regioselective catalytic epoxidation of alkenes by a novel ruthenium(II) complex under aerobic conditions

Epoxidation of alkenes by molecular oxygen is effected in high yields by catalysis of RuCl2(biox)2 using isobutyraldehyde as the co-reductant: the reaction is stereospecific and regioselective

Stereospecific and regioselective catalytic epoxidation of alkenes by a novel ruthenium(II) complex under aerobic conditions

Epoxidation of alkenes by molecular oxygen is effected in high yields by catalysis of RuCl2(biox)(2) using isobutyraldehyde as the co-reductant: the reaction is stereospecific and regioselective

A highly beta-stereoselective catalytic epoxidation of Delta(5)-unsaturated steroids with a novel ruthenium(II) complex under aerobic conditions

Catalytic beta-stereoselective epoxidation of Delta(5)-unsaturated steroid derivatives has been effected by a novel ruthenium(II) bioxazoline complex under aerobic conditions. The reactions are regio- and stereoselective. The reaction conditions provide the corresponding 5 beta,6 beta-epoxides with high degree of stereoselectivity (88-96%) in very good yields, while oxidation of steroid derivatives with peracids leads to 5 alpha,6 alpha-epoxides as the major products. The overall conformation of the steroid nucleus is nearly planar in the cholesteryl ester, while it is bent at the junction between the rings A and B in the 5 beta,6 beta-epoxide. This change from pseudo trans- to cis-stereochemistry of the A-B ring junction provides more room for the catalyst to approach from the beta-face of the steroidal skeleton

Highly Enantioselective Synthesis of 2,3-Dihydroquinazolinones through Intramolecular Amidation of Imines

Enantioselective synthesis of 2,3-dihydroquinazolinones (DHQZs) was accomplished using readily available Sc(III)-<i>inda</i>-pybox as the catalyst. This is the first report on the metal catalyzed asymmetric intramolecular amidation of imines to synthesize DHQZs

Stereodivergent Synthesis of 3‑Aminooxindole Derivatives Containing Vicinal Tetrasubstituted Stereocenters via the Mannich Reaction

A highly enantioselective stereodivergent synthesis of 3-aminooxindole derivatives was accomplished via asymmetric Mannich reaction between 2-substituted benzofuran-3-one and isatin-derived ketimines. Both <i>anti</i> and <i>syn</i>-selective chiral 3,3-disubstituted amino oxindoles bearing two adjacent tetrasubstituted stereogenic centers with high yield and excellent enantioselectivities were obtained using readily available cinchona-alkaloid derived organocatalysts. The control experiment revealed that oxygen atom present in the benzofuran ring played an important role in switching diastereodivergence. The obtained Mannich product was further transformed into a biologically important 2,3-dihydrobenzofuran derivative having three contiguous stereocenters with no loss of enantioselectivity

Enantioselective Synthesis of Dihydrospiro[indoline-3,4′-pyrano[2,3‑<i>c</i>]pyrazole] Derivatives via Michael/Hemiketalization Reaction

A new bifunctional squaramide organocatalyst derived from l-proline mediated the first enantioselective synthesis of dihydrospiro­[indoline-3,4′-pyrano­[2,3-<i>c</i>]­pyrazole] derivatives in excellent enantioselectivity by reacting pyrazolones with isatylidine β,γ-unsaturated α-ketoester. This new catalyst outperformed widely used thioureas and squaramides in inducing enantioselectivity

Highly Enantioselective Synthesis of 2,3-Dihydroquinazolinones through Intramolecular Amidation of Imines

Enantioselective synthesis of 2,3-dihydroquinazolinones (DHQZs) was accomplished using readily available Sc(III)-<i>inda</i>-pybox as the catalyst. This is the first report on the metal catalyzed asymmetric intramolecular amidation of imines to synthesize DHQZs

Stereodivergent Synthesis of 3‑Aminooxindole Derivatives Containing Vicinal Tetrasubstituted Stereocenters via the Mannich Reaction

A highly enantioselective stereodivergent synthesis of 3-aminooxindole derivatives was accomplished via asymmetric Mannich reaction between 2-substituted benzofuran-3-one and isatin-derived ketimines. Both <i>anti</i> and <i>syn</i>-selective chiral 3,3-disubstituted amino oxindoles bearing two adjacent tetrasubstituted stereogenic centers with high yield and excellent enantioselectivities were obtained using readily available cinchona-alkaloid derived organocatalysts. The control experiment revealed that oxygen atom present in the benzofuran ring played an important role in switching diastereodivergence. The obtained Mannich product was further transformed into a biologically important 2,3-dihydrobenzofuran derivative having three contiguous stereocenters with no loss of enantioselectivity

Stereodivergent Synthesis of 3‑Aminooxindole Derivatives Containing Vicinal Tetrasubstituted Stereocenters via the Mannich Reaction

A highly enantioselective stereodivergent synthesis of 3-aminooxindole derivatives was accomplished via asymmetric Mannich reaction between 2-substituted benzofuran-3-one and isatin-derived ketimines. Both <i>anti</i> and <i>syn</i>-selective chiral 3,3-disubstituted amino oxindoles bearing two adjacent tetrasubstituted stereogenic centers with high yield and excellent enantioselectivities were obtained using readily available cinchona-alkaloid derived organocatalysts. The control experiment revealed that oxygen atom present in the benzofuran ring played an important role in switching diastereodivergence. The obtained Mannich product was further transformed into a biologically important 2,3-dihydrobenzofuran derivative having three contiguous stereocenters with no loss of enantioselectivity