Microwave-Assisted K-10 Montmorillonite Clay–Mediated Knoevenagel Hetero-Diels–Alder Reactions: A Novel Protocol for the Synthesis of Polycyclic Pyrano[2,3,4-kl]xanthene Derivatives

Abstract

The intramolecular hetero-Diels–Alder reactions of 2-(cyclohex-2-enyloxy)benzaldehyde by Knoevenagel condensation with symmetrical 1,3-diones under three different conditions afforded the pyrano[2,3,4-kl]xanthene derivatives in a stereoselective manner in good yield. The structure of one of the products was unambiguously established by x-ray analysis.

Keywords:

• 1,3-Dione
• hetero-Diels–Alder reaction
• microwave
• pyrano xanthene

Notes

^a Reaction conditions: method A: toluene reflux; method B: toluene, MW; method C: K-10 montmorrilonite clay, MW.