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Modular Synthesis of Dehydroprolines by an Energy-Transfer Enabled Cloke-Wilson Rearrangement.

Angew Chem Int Ed Engl

December 2024

Department of Chemistry, Columbia University, New York, New York, 10027, United States.

A one-pot photocatalytic method is reported for the generation of dehydroprolines, valuable precursors to 5-aryl prolines. Imines, obtained via simple condensation of aminocyclopropane carboxylates (ACPC) with a broad range of aldehydes, were employed in this transformation without purification. We demonstrate this energy-transfer (EnT) enabled Cloke-Wilson-type rearrangement affords both the rare 1,2-dehydroprolines or the more thermodynamically favored 1,5-isomers with up to >20 : 1 selectivity in both directions, using an identical catalytic system from the same starting material.

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Conjugate addition of unstabilized Wittig-type phosphonium ylides to 1,1-diacceptor- and 1-acceptor-substituted alkenes is investigated by density functional theory and high-level (DLPNO-CCSD(T)) calculations. The results indicate that the initial conjugate addition step should be facile with barriers predicted to be between 0 and 21 kcal mol. Potential intramolecular follow-up reactions include the formation of acceptor-substituted cyclopropanes as well as the formation of dihydrofuran derivatives via intramolecular S2-type transition state structures.

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A facile and efficient approach for the synthesis of multisubstituted tetrahydropyridazines starting from cyclopropyl ketones and hydrazines has been developed. The transformation is chalcone-based and takes place via a Cloke-Wilson-type rearrangement-involved tandem reaction catalyzed by TfOH in HFIP.

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Cyclopropanes are of great synthetic value in heterocyclic chemistry due to their highly reactive nature. They are widely employed to synthesize various biologically active organic compounds. Generally, vinyl, carbonyl, imine, and alkylidene cyclopropanes are utilized as efficient synthetic precursors in organic synthesis.

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Regio- and Stereospecific Hydrative Cloke-Wilson Rearrangement.

Org Lett

November 2023

Chang-Kung Chuang Institute, School of Chemistry and Molecular Engineering, East China Normal University, 500 Dongchuan Lu, Shanghai 200241, China and.

The Cloke-Wilson rearrangement of unsymmetrical β-diketone-derived cyclopropanes inevitably yields a mixture of two 4-acylated 2,3-dihydrofuran regiomers. By using alkynes as masked acyls, TfNH-promoted Cloke-Wilson rearrangement of polysubstituted 1-(1-alkynyl)cyclopropyl ketones followed by alkyne hydration is described, regioselectively affording 2,3-dihydrofurans bearing 4-acyls nonequivalent to that involved in the Cloke-Wilson rearrangement. The 2,3-dihydrofuran rings with 2,3-diaryls are unexpectedly more stable than their diastereomers under the reaction conditions, guaranteeing the regiospecificity of this hydrative Cloke-Wilson rearrangement with high fidelity.

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