Enantioselective Enolate Protonation in Sulfa–Michael Addition to α-Substituted <i>N</i>-Acryloyloxazolidin-2-ones with Bifunctional Organocatalyst

Organocatalytic conjugate addition of thiols to α-substituted <i>N</i>-acryloyloxazolidin-2-ones followed by asymmetric protonation has been studied in the presence of <i>cinchona</i> alkaloid derived thioureas. Both of the enantiomers are accessible with the same level of enantioselectivity using pseudoenantiomeric quinine/quinidine derived catalysts. The addition/protonation products have been converted to useful biologically active molecules

Highly Enantioselective Organocatalytic Sulfa-Michael Addition to α,β-Unsaturated Ketones

A cinchona alkaloid-derived urea was found to be an efficient organocatalyst for catalyzing enantioselective conjugate addition between thiols and various α,β-unsaturated ketones to provide optically active sulfides with high chemical yields (up to >99%) and enantiomeric excess (up to >99% ee). The reaction was performed with 0.1 mol % of catalyst in toluene at room temperature. A transition state model has been proposed to explain the stereochemical outcome of the reaction

Highly Enantioselective Conjugate Addition of Malononitrile to 2‑Enoylpyridines with Bifunctional Organocatalyst

An efficient enantioselective conjugate addition of malononitrile to a range of β-substituted 2-enoylpyridines catalyzed by cinchona alkaloid-based bifunctional urea catalysts has been developed. Both enantiomers of the products could be achieved with the same level of enantioselectivity by using pseudoenantiomeric catalysts in up to 97% ee and in excellent yields. One of the enantioenriched products has been transformed to a highly functionalized piperidone derivative

Highly Stereoselective Synthesis of 2,6-<i>cis</i>-Substituted Tetrahydropyrans Using a One-Pot Sequential Catalysis

A catalytic highly diastereo- and enantioselective synthesis of 2,6-<i>cis</i>-substituted tetrahydropyrans was realized using a one-pot sequential catalysis involving Henry and oxa-Michael reactions. The nitroaldol products obtained in a highly enantioselective copper(II)-catalyzed Henry reaction between nitromethane and 7-oxo-hept-5-enals were subsequently treated with a catalytic amount of camphorsulfonic acid (CSA) to give the desired tetrahydropyran derivatives in excellent yields, diastereoselectivities (dr >99:1), and enantioselectivities (ee = 98–99%). The reaction can also be used for the high stereoselective synthesis of a <i>cis</i>-2,6-disubstituted morpholine

Reusable Supported Pyridine-Mediated Cascade Synthesis of <i>trans</i>-2,3-Dihydroindoles via In Situ-Generated <i>N</i>‑Ylide

Merrifield resin-anchored pyridines were prepared and applied as reusable mediators for trans-selective cascade synthesis of 2,3-dihydroindoles. The developed approach relied on in situ N-ylide formation followed by Michael substitution reactions. The cascade reaction was also carried out efficiently with simple pyridine. The products were further transformed into synthetically valuable compounds, and supported pyridine was reused for multiple cycles. Density functional theory calculations confirmed the trans-selectivity as the lower-energy pathway

Reusable Supported Pyridine-Mediated Cascade Synthesis of <i>trans</i>-2,3-Dihydroindoles via In Situ-Generated <i>N</i>‑Ylide

Merrifield resin-anchored pyridines were prepared and applied as reusable mediators for trans-selective cascade synthesis of 2,3-dihydroindoles. The developed approach relied on in situ N-ylide formation followed by Michael substitution reactions. The cascade reaction was also carried out efficiently with simple pyridine. The products were further transformed into synthetically valuable compounds, and supported pyridine was reused for multiple cycles. Density functional theory calculations confirmed the trans-selectivity as the lower-energy pathway

List–Barbas–Mannich Reaction Catalyzed by Modularly Designed Organocatalysts

The List–Barbas–Mannich reaction of ethyl (p-methoxyphenylimino)­acetate (p-methoxyphenyl = PMP) with unmodified aldehydes or ketones catalyzed by modularly designed organocatalysts (MDOs) that are self-assembled from proline and cinchona alkaloid thioureas (such as a quinidine-derived thiourea) produces the corresponding γ-oxo-α-amino acid derivatives in high yields and excellent stereoselectivities. No solvent is necessary for this reaction. Aldehydes are especially good substrates for this reaction: The reaction takes only a few minutes to yield the corresponding List–Barbas–Mannich products in excellent dr (up to >99:1) and ee values (up to >99% ee)

Recyclable Polymer Supported DMAP Catalyzed Cascade Synthesis of α‑Pyrones

Polymer-supported catalysts have emerged as one of the sustainable and cost-effective alternatives in organic synthetic chemistry. We have developed the first polymer-supported DMAP catalyzed one-pot synthesis of diversely substituted α-pyrones. The cascade approach involves C5 conjugate addition of 5H-oxazol-4-ones to α,β-unsaturated-β-ketoesters followed by lactonization/elimination

Recyclable Polymer Supported DMAP Catalyzed Cascade Synthesis of α‑Pyrones

Polymer-supported catalysts have emerged as one of the sustainable and cost-effective alternatives in organic synthetic chemistry. We have developed the first polymer-supported DMAP catalyzed one-pot synthesis of diversely substituted α-pyrones. The cascade approach involves C5 conjugate addition of 5H-oxazol-4-ones to α,β-unsaturated-β-ketoesters followed by lactonization/elimination