Enantioselective One-Pot Synthesis of α,β-Epoxy Ketones via Aerobic Oxidation of Cyclopropanols

An efficient, mild, and environmentally benign method was developed for the asymmetric synthesis of 2-oxyranyl ketones from easily available tertiary cyclopropanols. The one-pot protocol includes the aerobic oxidation of cyclopropanol derivatives catalyzed by Mn­(III) complexes followed by the poly-l-leucine-assisted stereoselective elimination of water from the intermediate peroxides with DBU to afford the corresponding epoxy ketones in high yields and good-to-excellent enantioselectivities (up to 97%)

Remote Activation of the Nucleophilicity of Isatin

The concept of the remote activation of reactivity was first applied in asymmetric organocatalysis. An isatin 3-phenylimine derivative acts as a donor in the thiourea catalyzed asymmetric addition to unsaturated 1,4-ketoesters, affording aza-Michael adducts in high enantiomeric purity and yield

Asymmetric Synthesis of Congested Spiro-cyclopentaneoxindoles via an Organocatalytic Cascade Reaction

Starting from simple alkylidene oxindoles and nitroketones, a highly stereoselective methodology was developed for the synthesis of spiro-cyclopentaneoxindoles with four consecutive stereogenic centers. Using an organocatalytic cascade of Michael and aldol reactions in the presence of a chiral thiourea catalyst products were obtained in moderate to high yields and excellent enantioselectivities. Nitro, ester, and hydroxyl groups were introduced to the spiro ring, which could be used to facilitate further functionalization of the products

Asymmetric Synthesis of Congested Spiro-cyclopentaneoxindoles via an Organocatalytic Cascade Reaction

Starting from simple alkylidene oxindoles and nitroketones, a highly stereoselective methodology was developed for the synthesis of spiro-cyclopentaneoxindoles with four consecutive stereogenic centers. Using an organocatalytic cascade of Michael and aldol reactions in the presence of a chiral thiourea catalyst products were obtained in moderate to high yields and excellent enantioselectivities. Nitro, ester, and hydroxyl groups were introduced to the spiro ring, which could be used to facilitate further functionalization of the products

Organocatalytic Asymmetric Synthesis of 3‑Chlorooxindoles Bearing Adjacent Quaternary–Tertiary Centers

A new methodology was developed for the synthesis of enantiomerically enriched 3,3-disubstituted 3-chlorooxindoles <b>3</b> via a Michael addition of 3-chloroxindoles to nitroolefins <b>2</b>, catalyzed by chiral squaramide <b>10</b>. Products with adjacent quaternary–tertiary centers were isolated in excellent yields (up to 99%), high diastereoselectivities (up to 11:1), and enantiomeric purities (up to 92%). This is the first example where 3-chloroxoindoles <b>1</b> have been used as nucleophiles in a highly stereoselective organocatalytic reaction

Organocatalytic Asymmetric Synthesis of 3‑Chlorooxindoles Bearing Adjacent Quaternary–Tertiary Centers

A new methodology was developed for the synthesis of enantiomerically enriched 3,3-disubstituted 3-chlorooxindoles <b>3</b> via a Michael addition of 3-chloroxindoles to nitroolefins <b>2</b>, catalyzed by chiral squaramide <b>10</b>. Products with adjacent quaternary–tertiary centers were isolated in excellent yields (up to 99%), high diastereoselectivities (up to 11:1), and enantiomeric purities (up to 92%). This is the first example where 3-chloroxoindoles <b>1</b> have been used as nucleophiles in a highly stereoselective organocatalytic reaction

Diastereoselective Multicomponent Cascade Reaction Leading to [3.2.0]-Heterobicyclic Compounds

A general three-component triple cascade reaction through an iminium–enamine–iminium sequential activation initiated by a hetero-Michael addition to α,β-unsaturated aldehydes affords [3.2.0]­heterobicycles in high diastereoselectivity. The rate and diastereoselectivity of the reaction depended on the (<i>E</i>)-4-heterocrotonate and size of the secondary amine. The enantiomers of the major diastereoisomer of oxa- and azabicyclo[3.2.0]­heptane derivatives were separated by enzymatic kinetic resolution with immobilized <i>Candida antarctica</i> Lipase B (CALB), with <i>E</i> values up to 153. The absolute configuration of the nonacylated enantiomer of oxabicyclo[3.2.0]­heptane was determined by single crystal X-ray analysis

Diastereoselective Multicomponent Cascade Reaction Leading to [3.2.0]-Heterobicyclic Compounds

A general three-component triple cascade reaction through an iminium–enamine–iminium sequential activation initiated by a hetero-Michael addition to α,β-unsaturated aldehydes affords [3.2.0]­heterobicycles in high diastereoselectivity. The rate and diastereoselectivity of the reaction depended on the (<i>E</i>)-4-heterocrotonate and size of the secondary amine. The enantiomers of the major diastereoisomer of oxa- and azabicyclo[3.2.0]­heptane derivatives were separated by enzymatic kinetic resolution with immobilized <i>Candida antarctica</i> Lipase B (CALB), with <i>E</i> values up to 153. The absolute configuration of the nonacylated enantiomer of oxabicyclo[3.2.0]­heptane was determined by single crystal X-ray analysis

3-Chlorooxindoles: versatile starting materials for asymmetric organocatalytic synthesis of spirooxindoles

3-Chlorooxoindoles have emerged as versatile precursors in the synthesis of spirocyclopropyl oxindoles. High enantio- and diastereoselectivity was attained under conditions of both iminium/enamine and H-bonding catalysis