title: Unexpected formation of 1-diethylaminobutadiene in photosensitized oxidation of triethylamine induced by 2,3-dihydro-oxoisoaporphine dyes. A 1H NMR and isotopic exchange study.
abstract: [reaction: see text] Photoreduction of oxoisoaporphine dyes occurs via a stepwise mechanism of electron-proton-electron transfer that leads to the N-hydrogen oxoisoaporphine anion. When triethylamine, TEA, was used as the electron donor in anaerobic conditions, 1-diethylaminobutadiene, DEAB, was one of the oxidation products of TEA, among diethylamine and acetaldehyde. DEAB was identified by (1)H NMR and GC-MS experiments by comparison with the authentic 1-diethylaminobutadiene. This is the first report of a butadienyl derivative formed in the dye-sensitized photooxidation of TEA. In addition, isotopic exchange experiments with TEA-d(15) and D(2)O show that the hydrogens at carbon-2 and carbon-4 of the butadienyl moiety are exchangeable. The observed isotopic exchange pattern could be explained by the head-to-tail coupling of an N,N-diethylvinylamine intermediate that exchanges hydrogens at the C-beta via the enammonium ion.
authors.affiliation: Departamento Química Orgánica y Fisicoquímica and CEPEDEQ, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile Casilla 233, Santiago. jrfuente@ciq.uchile.cl
authors.forename: Julio R
authors.initials: JR
authors.lastname: De la Fuente
authors.forename: Carolina
authors.initials: C
authors.lastname: Jullian
authors.forename: Claudio
authors.initials: C
authors.lastname: Saitz
authors.forename: Verónica
authors.initials: V
authors.lastname: Neira
authors.forename: Oscar
authors.initials: O
authors.lastname: Poblete
authors.forename: Eduardo
authors.initials: E
authors.lastname: Sobarzo-Sánchez