Synthesis of Functionalized Pyrrolizidines/Pyrrolidines Incorporating a Spirooxindole Motif through [3+2] Cycloaddition
摘要:
Dimethyl 2-(aryloxy)fumarates and dimethyl 2-(alkyl- or arylthio)fumarates are shown to be efficient dipolarophiles in 1,3-dipolar cycloaddition reaction with azomethine ylides, which are generated by the reaction of isatin with the secondary amino acids proline or sarcosine. In these reactions, dimethyl 2-(alkyl- or arylthio)fumarates afforded spirooxindolopyrrolizidines or -pyrrolidines in high yields with excellent regioselectivities, while dimethyl 2-(aryloxy)fumarates produced mixtures of regioisomers. DFT calculations at the B3LYP/6-31G(d,p) level were consistent with the observed results. Tri- and tetracyclic compounds were obtained through regio- and stereoselective intramolecular cycloaddition of O-vinylic salicylaldehyde with secondary amino acids.
Substituted 4H-1-benzopyran-4-ones (chromones): synthesis via palladium-catalysed coupling of their halogeno derivatives with alkenes
作者:Stephen G. Davies、Bryan E. Mobbs、Christopher J. Goodwin
DOI:10.1039/p19870002597
日期:——
into the carbon–halogen bond. The resultant species undergo coupling with alkenes leading to vinylated chromones. Vinylation occurs regiospecifically at the original site of bromination and therefore provides a method for the clean introduction of substituents into the chromone ring system. An anomalous reaction of a dibrominated chromone leading to a ring-opened product is described.