160348-48-1Relevant academic research and scientific papers
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.
5-Chloropyrazole-4-carbaldehydes as Synthons for Intramolecular 1,3-Dipolar Cycloadditions
L'abbe, Gerrit,Emmers, Sabine,Dehaen, Wim,Dyall, Leonard K.
, p. 2553 - 2558 (2007/10/02)
A general method is described to transform the readily available title compounds into tri- and tetracyclic heterocycles, first by substituting the chlorine atom by an unsaturated thiolate or alkoxide, and then by modifying the aldehyde function into a 1,3-dipole.As 1,3-dipoles, nitrile oxide, nitrone, nitrile imine, azomethine ylide and azomethine imine groups were generated from the 5-allylsulfanyl-4-formylpyrazole 7, which resulted in intramolecular cycloaddition and formation of the heterocycles shown in Scheme 2.The other pyrazoles 22, 23, 26, 30 and 33 were converted via intramolecular nitrile oxide cycloaddition (INOC) into fused dihydroisoxazoles.A limitation to the method is the Claisen rearrangement which occurs when the allyl ether 26 or the prop-2-ynyl ether 30 is used.
