Enders D, Grossmann A, Gieraths B, Düzdemir M, Merkens C. Organocatalytic one-pot asymmetric synthesis of 4H,5H-pyrano[2,3-c]pyrazoles.
Org Lett 2012;
14:4254-7. [PMID:
22852800 DOI:
10.1021/ol301983f]
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Abstract
An efficient one pot asymmetric synthesis of tetrahydropyrano[2,3-c]pyrazoles has been developed. This class of biologically active heterocycles can be obtained via a secondary amine catalyzed asymmetric Michael/Wittig/oxa-Michael reaction sequence. Remarkably, the title compounds were accessible in good to very good yields and very good to excellent enantioselectivities after a single purification step.
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