A Base-Catalyzed, Domino Aldol/<i>hetero</i>-Diels–Alder Synthesis of Tricyclic Pyrano[3,4‑<i>c</i>]chromenes in Glycerol

The domino aldol/hetero-Diels–Alder synthesis of some new tricyclic pyrano­[3,4-c]­chromene derivatives has been achieved successfully after assembling a variety of acyclic or cyclic monoketones with prenyl ether-tethered aldehydes in the presence of 1,8-diazabicyclo[5.4.0]­undec-7-ene in glycerol at 120 °C. The hitherto unreported stereochemical outcome of this synthetic sequence was studied and established on the basis of single-crystal X-ray diffraction data and 2D NMR NOESY spectroscopy along with the isolation and characterization of the intermediate Aldol condensation product.