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Enantioselective synthesis of pyrazolone-fused spirocyclohexenols by the secondary amine-catalyzed cascade reaction of α,β-unsaturated aldehydes with α-arylidene pyrazolinones is reported. This formal [3 + 3] organocascade reaction proceeds through a vinylogous… Click to show full abstract
Enantioselective synthesis of pyrazolone-fused spirocyclohexenols by the secondary amine-catalyzed cascade reaction of α,β-unsaturated aldehydes with α-arylidene pyrazolinones is reported. This formal [3 + 3] organocascade reaction proceeds through a vinylogous Michael-aldol sequence to furnish the spiroheterocycles with three stereocenters including an all-carbon quaternary center in good yields and selectivities. The catalytic generation of α,β-unsaturated iminium ions from enals and tandem dienolate/enolate formation from pyrazolinones are the key for the success of this spiroannulation reaction.
Journal Title: Organic letters
Year Published: 2017
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