432491-25-3Relevant articles and documents
Diastereoselective intramolecular hetero Diels-Alder approach towards polycyclic heterocycles
Ceulemans, Erik,Voets, Marieke,Emmers, Sabine,Uytterhoeven, Koen,Meervelt, Luc Van,Dehaen, Wim
, p. 531 - 544 (2007/10/03)
Several different heterocyclic aldehydes, derived from pyrazole, pyrimidine, pyridine, indole and thiazole, were converted to polyheterocyclic compounds containing four to seven rings. The key steps in the sequence were a Knoevenagel condensation of the aldehyde and a heterocyclic carbonyl compound, such as pyrazolone and isoxazolone, followed by an intramolecular hetero Diels-Alder reaction. Most final products were isolated with high yield and diastereoselecivity. The isoxazolo fused cycloadducts formed interesting spiro-adducts upon heating. The cis nature of the bridging hydrogens of the heterocycles was evidenced by X-ray diffraction analysis.
