title: Cross-benzoin and Stetter-type reactions mediated by KOtBu-DMF via an electron-transfer process.
abstract: The condensation of aromatic α-diketones (benzils) with aromatic aldehydes (benzoin-type reaction) and chalcones (Stetter-type reaction) in DMF in the presence of catalytic (25 mol%) KOtBu is reported. Both types of umpolung processes proceed with good efficiency and complete chemoselectivity. On the basis of spectroscopic evidence (MS analysis) of plausible intermediates and literature reports, the occurrence of different ionic pathways have been evaluated to elucidate the mechanism of a model cross-benzoin-like reaction along with a radical route initiated by an electron-transfer process to benzil from the carbamoyl anion derived from DMF. This mechanistic investigation has culminated in a different proposal, supported by calculations and a trapping experiment, based on double electron-transfer to benzil with formation of the corresponding enediolate anion as the key reactive intermediate. A mechanistic comparison between the activation modes of benzils in KOtBu-DMF and KOtBu-DMSO systems is also described.
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences - University of Ferrara, Via Fossato di Mortara 17, I-44121 Ferrara, Italy. alessandro.massi@unife.it alessandro.venturini@isof.cnr.it.
authors.forename: Daniele
authors.initials: D
authors.lastname: Ragno
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences - University of Ferrara, Via Fossato di Mortara 17, I-44121 Ferrara, Italy. alessandro.massi@unife.it alessandro.venturini@isof.cnr.it.
authors.forename: Anna
authors.initials: A
authors.lastname: Zaghi
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences - University of Ferrara, Via Fossato di Mortara 17, I-44121 Ferrara, Italy. alessandro.massi@unife.it alessandro.venturini@isof.cnr.it.
authors.forename: Graziano
authors.initials: G
authors.lastname: Di Carmine
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences - University of Ferrara, Via Fossato di Mortara 17, I-44121 Ferrara, Italy. alessandro.massi@unife.it alessandro.venturini@isof.cnr.it.
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Giovannini
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences - University of Ferrara, Via Fossato di Mortara 17, I-44121 Ferrara, Italy. alessandro.massi@unife.it alessandro.venturini@isof.cnr.it.
authors.forename: Olga
authors.initials: O
authors.lastname: Bortolini
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences - University of Ferrara, Via Fossato di Mortara 17, I-44121 Ferrara, Italy. alessandro.massi@unife.it alessandro.venturini@isof.cnr.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Fogagnolo
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences - University of Ferrara, Via Fossato di Mortara 17, I-44121 Ferrara, Italy. alessandro.massi@unife.it alessandro.venturini@isof.cnr.it.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Molinari
authors.affiliation: ISOF-CNR, Via P. Gobetti 101, I-40129 Bologna, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Venturini
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences - University of Ferrara, Via Fossato di Mortara 17, I-44121 Ferrara, Italy. alessandro.massi@unife.it alessandro.venturini@isof.cnr.it.
authors.forename: Alessandro
authors.identifier: http://orcid.org/0000-0001-8303-5441
authors.initials: A
authors.lastname: Massi