Organocatalytic One-Pot Asymmetric Synthesis of 4<i>H</i>,5<i>H</i>‑Pyrano[2,3‑<i>c</i>]pyrazoles

An efficient one pot asymmetric synthesis of tetrahydropyrano[2,3-<i>c</i>]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