title: Stereoselective Synthesis of 1,3-Diaminotruxillic Acid Derivatives: An Advantageous Combination of C-H-ortho-Palladation and On-Flow [2+2]-Photocycloaddition in Microreactors.
abstract: The stereoselective synthesis of ε-isomers of dimethyl esters of 1,3-diaminotruxillic acid in three steps is reported. The first step is the ortho-palladation of (Z)-2-aryl-4-aryliden-5(4H)-oxazolones 1 to give dinuclear complexes 2 with bridging carboxylates. The reaction occurs through regioselective activation of the ortho-CH bond of the 4-arylidene ring in carboxylic acids. The second step is the [2+2]-photocycloaddition of the CC exocyclic bonds of the oxazolone skeleton in 2 to afford the corresponding dinuclear ortho-palladated cyclobutanes 3. This key step was performed very efficiently by using LED light sources with different wavelengths (465, 525 or 625 nm) in flow microreactors. The final step involved the depalladation of 3 by hydrogenation in methanol to afford the ε-1,3-diaminotruxillic acid derivatives as single isomers.
authors.affiliation: Centro Universitario de la Defensa, Academia General Militar, 50090 Zaragoza (Spain).
authors.forename: Elena
authors.initials: E
authors.lastname: Serrano
authors.affiliation: Instituto Regional de Investigación Científica Aplicada (IRICA), Universidad de Castilla La Mancha, Avenida Camilo José cela s/n, 13071 Ciudad Real (Spain).
authors.forename: Alberto
authors.initials: A
authors.lastname: Juan
authors.affiliation: Instituto de Síntesis QuímicayCatálisis Homogénea (ISQCH), CSIC-Universidad de Zaragoza, Fac. Ciencias, Edificio D, Pedro Cerbuna 12, 50009 Zaragoza (Spain).
authors.forename: Angel
authors.initials: A
authors.lastname: García-Montero
authors.affiliation: Servicios Centrales Investigación, Universidad de Alicante, 03690 Alicante (Spain).
authors.forename: Tatiana
authors.initials: T
authors.lastname: Soler
authors.affiliation: E.T.S. Ingenieros Industriales, Universidad de Castilla-La Mancha, Avenida Camilo José cela s/n, 13071 Ciudad Real (Spain).
authors.forename: Francisco
authors.initials: F
authors.lastname: Jiménez-Márquez
authors.affiliation: Instituto de Síntesis QuímicayCatálisis Homogénea (ISQCH), CSIC-Universidad de Zaragoza, Fac. Ciencias, Edificio D, Pedro Cerbuna 12, 50009 Zaragoza (Spain). cativiela@unizar.es.
authors.forename: Carlos
authors.initials: C
authors.lastname: Cativiela
authors.affiliation: Instituto Regional de Investigación Científica Aplicada (IRICA), Universidad de Castilla La Mancha, Avenida Camilo José cela s/n, 13071 Ciudad Real (Spain). MariaVictoria.Gomez@uclm.es.
authors.forename: M Victoria
authors.initials: MV
authors.lastname: Gomez
authors.affiliation: Instituto de Síntesis QuímicayCatálisis Homogénea (ISQCH), CSIC-Universidad de Zaragoza, Fac. Ciencias, Edificio D, Pedro Cerbuna 12, 50009 Zaragoza (Spain). esteban@unizar.es.
authors.forename: Esteban P
authors.initials: EP
authors.lastname: Urriolabeitia
keywords: CH activation; lactones; microreactors; palladium; photochemistry