The tandem cyclization-cycloaddition reactions of α-diazo ketones in the presence of rhodium(II) acetate, rhodium(II) octanoate or copper(II) acetyl acetonate as catalyst were performed in different imidazole based ionic liquids as solvent. A successful generation of the transient five- or six-membered-ring carbonyl ylides, followed by the 1,3-dipolar cycloaddition with olefin or carbonyl functional groups in ionic liquid is described to furnish the oxa and dioxa-bridged polycyclic systems with high stereoselectivity. Significant advantages of this process are the recovery of rhodium catalyst, the re-use of ionic liquid, replacement of hazardous organic solvents and the resulting high stereoselectivity. © 2004 Elsevier Ltd. All rights reserved.
Muthusamy, S., & Gnanaprakasam, B. (2005). Ionic liquids as a convenient recyclable medium for the generation of transient carbonyl ylides: Syntheses of oxa and dioxa-bridged polycyclic systems. Tetrahedron, 61(5), 1309–1315. https://doi.org/10.1016/j.tet.2004.11.008