One-pot asymmetric synthesis of a spiro[dihydrofurocoumarin/pyrazolone] scaffold by a Michael addition/I2-mediated
Ai-Bao Xia1, Xiao-Long Zhang1, Cheng-Ke Tang1
1Catalytic Hydrogenation Research Centre, State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Zhejiang University of Technology, Hangzhou, 310014, China. chrc@zjut.edu.cn.
Abstract:
An asymmetric formal one-pot reaction of 4-hydroxycoumarins with unsaturated pyrazolones has been developed by merging a chiral bifunctional organocatalyst with molecular iodine, which furnished a series of optically active spiro[dihydrofurocoumarin/pyrazolone] heterocycles with spiro quaternary stereogenic centers in moderate to excellent yields (up to 99%) with excellent diastereoselectivities (up to >99 : 1 dr) and good to excellent enantioselectivities (up to 99% ee). The application in the gram-scale synthesis of chiral spiro[dihydrofurocoumarin/pyrazolone] compounds was also successfully realized.
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