Selective 6π‐Electrocyclization of N‐Vinyl‐α,β‐Unsaturated Nitrones to Prepare Polysubstituted Pyridine Derivatives

Chinese Journal of Chemistry, Год журнала: 2025, Номер unknown

Опубликована: Март 7, 2025

Comprehensive Summary Herein, we have developed a facile method for the synthesis of various polysubstituted pyridine derivatives through selective 6π‐electrocyclization N ‐vinyl‐ α , β ‐unsaturated nitrones. It was found that gold catalysts promoted carbon‐6π‐electrocyclization nitrones to afford 6‐alkenyl ‐oxides in 43%—75% yields, whereas copper facilitated oxygen‐6π‐electrocyclization give 6‐epoxy pyridines 41%—83% yields. The present features broad substrate scope, good functional group tolerance, high cyclization selectivity, and diversity scaffolds.

Язык: Английский

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Iron(III) and BF₃·OEt₂-Promoted O-Transfer Reaction of N-Aryl-α,β-Unsaturated Nitrones to Prepare Difluoroboron β-Ketoiminates

Organic Letters, Год журнала: 2024, Номер 26(15), С. 3060 - 3064

Опубликована: Март 29, 2024

We described an iron(III) and BF3·OEt2-promoted oxygen transfer reaction of N-aryl-α,β-unsaturated nitrones to prepare various N,O-difluoroboron β-ketoiminates in good yields ranging from 24% 87%. Control experiments revealed that the enaminone was vital intermediate for formation β-ketoiminates, combined with BF3·OEt2 played as cocatalyst promote through intramolecular cyclization N–O bond cleavage. More importantly, estrone-derived β-ketoiminate easily prepared 40% yield estrone four steps.

Язык: Английский

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Water-mediated dipole transfer and deoxygenation of nitrones: Experimental and computational mechanistic insights

Journal of Molecular Structure, Год журнала: 2025, Номер unknown, С. 141947 - 141947

Опубликована: Март 1, 2025

Язык: Английский

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Nickel(II)-Catalyzed Unexpected [3 + 2] Cycloaddition/[3,3]-Rearrangement of N-Vinyl α,β-Unsaturated Nitrones with 2-Alkynyl Quinazolinones

Organic Letters, Год журнала: 2025, Номер unknown

Опубликована: Май 15, 2025

A nickel(II)-catalyzed unexpected [3 + 2] cycloaddition/[3,3]-rearrangement cascade reaction was developed for the preparation of various polysubstituted 1-pyrroline-tethered quinazolinones containing three contiguous stereocenters in moderate to good yields with high diastereoselectivity from N-vinyl cinnamaldehyde nitrones and 2-alkynyl quinazolinones. Polysubstituted pyrrolizine-tethered were obtained when replaced by chalcone nitrones. The present method features a broad substrate scope, [3,3]-rearrangement selectivity diastereoselectivity, two substituent bifurcated types N-heterocycles.

Язык: Английский

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Yb(OTf)₃‐Catalyzed Asymmetric [3+3] Cycloaddition of N‐Vinyl Nitrones with Activated Cyclopropanes to Prepare 1,2‐Oxazines

Chinese Journal of Chemistry, Год журнала: 2024, Номер unknown

Опубликована: Ноя. 25, 2024

Comprehensive Summary We described a Yb(OTf) 3 combined with Pybox ligand catalyzed asymmetric [3+3] cycloaddition of N ‐vinyl cinnamaldehyde nitrones activated cyclopropanes to prepare various functionalized 1,2‐oxazines in 24%—95% yields and 22%—96% ee. Experimental results revealed that the reaction underwent domino cycloaddition, dealkenylation, aza‐1,4‐addition three steps. The chiral 1,2‐oxazine could be obtained gram scales easily converted into scaffolds. present method features broad substrate scope, good functional group compatibility, three‐component reaction, cyclopropanes.

Язык: Английский

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Asymmetric [3+3] Cycloaddition of N‐Vinyl Oxindole Nitrones with 2‐Indolylmethanols to Prepare Spirooxindole[1,2]oxazines

Advanced Synthesis & Catalysis, Год журнала: 2024, Номер unknown

Опубликована: Авг. 1, 2024

Abstract We describe a chiral phosphoric acid (CPA) catalyzed asymmetric [3+3] cycloaddition of N ‐viny oxindole nitrones with 2‐indolylmethanols to prepare various spirooxindole[1,2]oxazines in 43–93% yields and 88:12–97:3 enantiomeric ratios. Experimental results revealed that the addition hexafluoroisopropanol (HFIP) played important roles help CPA control reaction reactivity enantioselectivity. The present method features construction tetrasubstituted carbon stereocenter example ‐vinyl cycloaddition.

Язык: Английский

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