title: Iron(III)-promoted aza-Prins-cyclization: direct synthesis of six-membered azacycles.
abstract: [reaction: see text] A new iron(III) halide-promoted aza-Prins cyclization between gamma,delta-unsaturated tosylamines and aldehydes provides six-membered azacycles in good to excellent yields. The process is based on the consecutive generation of gamma-unsaturated-iminium ion and further nucleophilic attack by the unsaturated carbon-carbon bond. Homoallyl tosylamine leads to trans-2-alkyl-4-halo-1-tosylpiperidine as the major isomer. In addition, the alkyne aza-Prins cyclization between homopropargyl tosylamine and aldehydes gives 2-alkyl-4-halo-1-tosyl-1,2,5,6-tetrahydropyridines as the only cyclic products.
authors.affiliation: Instituto Universitario de Bio-Organica Antonio Gonzalez, Universidad de La Laguna, C/Astrofísico Francisco Sanchez 2, 38206 La Laguna, Tenerife, Spain.
authors.forename: Rubén M
authors.initials: RM
authors.lastname: Carballo
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Ramírez
authors.forename: Matías L
authors.initials: ML
authors.lastname: Rodríguez
authors.forename: Víctor S
authors.initials: VS
authors.lastname: Martín
authors.forename: Juan I
authors.initials: JI
authors.lastname: Padrón