title: N-heterocyclic carbene catalyzed addition of aldehydes to diazo compounds: stereoselective synthesis of N-acylhydrazones.
abstract: An innovative stereoselective synthesis of N-acylhydrazones via an unprecedented N-heterocyclic carbene catalyzed addition of aldehydes to diazo compounds is presented. Enals exclusively afforded N-acylhydrazones, in yields up to 91%. The observed regioselectivity was traced back to the reaction of the vinylogous Breslow intermediate via the acyl anion pathway over competing homoenolate, enol, and acyl azolium pathways. This unusual reaction profile was studied based on DFT calculations, which revealed that the reaction is under orbital control, rather than being ruled by charge.
authors.affiliation: Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Fábio M F
authors.initials: FM
authors.lastname: Santos
authors.forename: João N
authors.initials: JN
authors.lastname: Rosa
authors.forename: Vânia
authors.initials: V
authors.lastname: André
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Duarte
authors.forename: Luís F
authors.initials: LF
authors.lastname: Veiros
authors.forename: Pedro M P
authors.initials: PM
authors.lastname: Gois
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D001391:Azo Compounds / Q000737:chemistry*; D002384:Catalysis; D006835:Hydrazones / Q000138:chemical synthesis* / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D001391:Azo Compounds; D006835:Hydrazones; C030011:carbene; D008697:Methane