An enantioselective synthesis of spiropyrazolone-fused dihydrofuran-naphthoquinones is first demonstrated via a Michael addition/Chlorination/Nucleophilic substitution sequence. The reactions of 2-hydroxy-1,4-naphthoquinone and α,β-unsaturated pyrazolones in the presence of the cinchona alkaloid derived hydrogen-bonding catalyst and NCS provide spiropyrazolone-fused 2,3-dihydronaphtho[2,3-]furan-4,9-diones bearing contiguous stereocenters, of which one is the spiro quaternary stereocenter in high yields with exclusive diastereoselectivity and good to excellent enantioselectivities.
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Asymmetric Synthesis of Spiropyrazolone-Fused Dihydrofuran-naphthoquinones Bearing Contiguous Stereocenters via a Michael Addition/Chlorination/Nucleophilic Substitution Sequence.
J Org Chem
April 2023
School of Pharmacy, Shanxi Medical University, Taiyuan, Shanxi 030001, China.
An enantioselective synthesis of spiropyrazolone-fused dihydrofuran-naphthoquinones is first demonstrated via a Michael addition/Chlorination/Nucleophilic substitution sequence. The reactions of 2-hydroxy-1,4-naphthoquinone and α,β-unsaturated pyrazolones in the presence of the cinchona alkaloid derived hydrogen-bonding catalyst and NCS provide spiropyrazolone-fused 2,3-dihydronaphtho[2,3-]furan-4,9-diones bearing contiguous stereocenters, of which one is the spiro quaternary stereocenter in high yields with exclusive diastereoselectivity and good to excellent enantioselectivities.
View Article and Find Full Text PDFEnantioselective Synthesis of Spiropyrazolone-Fused Cyclopenta[]chromen-4-ones Bearing Five Contiguous Stereocenters via (3+2) Cycloaddition.
J Org Chem
September 2021
Department of Chemistry, National Taiwan Normal University, 88, Sec. 4, Tingchow Road, Taipei 11677, Taiwan R.O.C.
An enantioselective synthesis of spiropyrazolone-fused cyclopenta[]chromen-4-ones is demonstrated via a (3+2) cycloaddition reaction. The reactions of 3-homoacylcoumarins and α,β-unsaturated pyrazolones in the presence of the cinchona-alkaloid derived hydrogen-bonding catalyst provide aforementioned spiropyrazolone-chromenone adducts bearing five contiguous stereocenters, of which one is the spiro all-carbon quaternary stereocenter in high yields (up to 98%) with good to excellent stereoselectivities (>25:1 dr and up to 99% ee). This one-pot methodology could also be practically demonstrated on a gram-scale with similar efficacy.
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