Solvent effect on the reactivity of l,10-phenanthroline-5,6-dione towards diazomethane

In an aprotic medium, such as THF, Et2O or CH2Cl2, the reaction of 1,10-phe nanthroline-5,6-dione with diazomethane gave 5,6-methylenedioxy- 1,10-phena nthroline as the only product. In contrast, in a protic solvent, such as 2- propanol or ethanol, the nucleophilic attack of CH2N2 occurred on carbonyl carbons, resulting in the formation of dispiro[5,6-dihydro-1,10-phenanthrol ine-5,6-dioxirane] as the main product. When the reaction with CH2N2 was ca rried out in methanol, the only product which could be isolated from the re action mixture, dimethyl 2,2'-bipyridine-3,3'-dicarboxylate, resulted from a break of the C(5)-C(6) bridge. (C) 2001 Elsevier Science Ltd. All rights reserved.