Asymmetric Synthesis of Spiropyrazolone-Fused Dihydrofuran-naphthoquinones Bearing Contiguous Stereocenters via a Michael Addition/Chlorination/Nucleophilic Substitution Sequence
作者:Gaihui Li、Hongyu Zhang、Guoshun Zhang、Bei Wei、Bin Liu、Heng Song、Qingshan Li、Shurong Ban
DOI:10.1021/acs.joc.2c03013
日期:——
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-b]furan-4
Acrylates, crotonate, and fumarates derivedfrom cinchona alkaloids were easily prepared. The highly re-facial selective additions of the dienophiles derivedfrom cinchonidine or quinine to some dienes were achieved in the presence of SnCl4. Similarly, si-facial selective additions were also achieved by the use of cinchonine instead of cinchonidine or quinine as a chiral auxiliary alcohol with equal