Stereoselective Synthesis of 1,3‐Diaminotruxillic Acid Derivatives: An Advantageous Combination of CH‐ortho‐Palladation and On‐Flow [2+2]‐Photocycloaddition in Microreactors |
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| Authors: | Dr. Elena Serrano Dr. Alberto Juan Angel García‐Montero Dr. Tatiana Soler Francisco Jiménez‐Márquez Prof. Dr. Carlos Cativiela Dr. M. Victoria Gomez Dr. Esteban P. Urriolabeitia |
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| Affiliation: | 1. Centro Universitario de la Defensa, Academia General Militar, 50090 Zaragoza (Spain);2. Instituto Regional de Investigación Científica Aplicada (IRICA), Universidad de Castilla La Mancha, Avenida Camilo José cela s/n, 13071 Ciudad Real (Spain);3. Instituto de Síntesis QuímicayCatálisis Homogénea (ISQCH), CSIC‐Universidad de Zaragoza, Fac. Ciencias, Edificio D, Pedro Cerbuna 12, 50009 Zaragoza (Spain);4. Servicios Centrales Investigación, Universidad de Alicante, 03690 Alicante (Spain);5. E.T.S. Ingenieros Industriales, Universidad de Castilla‐La Mancha, Avenida Camilo José cela s/n, 13071 Ciudad Real (Spain) |
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| 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. |
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| Keywords: | C H activation lactones microreactors palladium photochemistry |
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