title: Oxazolium-derived azomethine ylides. External oxazole activation and internal dipole trapping in the synthesis of an aziridinomitosene.
abstract: Intermolecular alkylation of the aziridinyl oxazole 20 using PhSO(2)CH(2)CH(2)OTf is possible despite the presence of potentially nucleophilic aziridine nitrogen. The resulting oxazolium salt 22 reacts with BnNMe(3)(+)CN(-) to produce the azomethine ylide 24b via electrocyclic ring opening of an oxazoline 23b. Internal cycloaddition affords 26 in 66% yield. After saponification and base-induced cleavage of the N-phenylsulfonylethyl group, conventional cyclization provides access to 33. Deprotection and DDQ oxidation completes the synthesis of the aziridinomitosene derivative 9b. The starting cis-disubstituted aziridine ester 16 can be prepared by the aza-Darzens reaction of 15 with tert-butyl chloroacetate.
authors.affiliation: Chemistry Department, University of Wisconsin, Madison, Wisconsin 52706, USA. edved@umich.edu
authors.forename: E
authors.initials: E
authors.lastname: Vedejs
authors.forename: D W
authors.initials: DW
authors.lastname: Piotrowski
authors.forename: F C
authors.initials: FC
authors.lastname: Tucci
mesh_terms: D001388:Aziridines / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D010080:Oxazoles / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
chemical_list: D001388:Aziridines; D010080:Oxazoles; C413848:aziridinomitosene