title: PIFA-mediated oxidative cyclization of 1-carbamoyl-1-oximylcycloalkanes: synthesis of spiro-fused pyrazolin-5-one N-oxides.
abstract: A convenient and efficient synthesis of spiro-fused pyrazolin-5-one N-oxides starting from readily available 1-carbamoyl-1-oximylcycloalkanes is developed. This general protocol features a novel and facile way for access to the five-membered azaheterocycles by formation of a new N-N single bond. The key cyclization step utilizes the formation of an N-oxonitrenium intermediate, mediated by the hypervalent iodine reagent PIFA, and its subsequent intramolecular trapping by the amide moiety under rather mild experimental conditions.
authors.affiliation: Department of Chemistry, Northeast Normal University, Changchun, 130024, China.
authors.forename: Kewei
authors.initials: K
authors.lastname: Wang
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Fu
authors.forename: Jinying
authors.initials: J
authors.lastname: Liu
authors.forename: Yongjiu
authors.initials: Y
authors.lastname: Liang
authors.forename: Dewen
authors.initials: D
authors.lastname: Dong
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D003500:Cyclization; D005463:Fluoroacetates; D007462:Iodobenzenes; D008958:Models, Molecular; D015394:Molecular Structure; D047069:Pyrazolones / Q000138:chemical synthesis* / Q000737:chemistry; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D014269:Trifluoroacetic Acid / Q000737:chemistry
chemical_list: D000473:Alkanes; D005463:Fluoroacetates; D007462:Iodobenzenes; D047069:Pyrazolones; D013141:Spiro Compounds; C517666:phenyliodine(III) bis(trifluoroacetate); D014269:Trifluoroacetic Acid