Volume 2014, Issue 28 p. 6263-6271
Full Paper

Palladium-Catalyzed Regioselective 5-exo-O-Cyclization/Oxidative Heck Cascades from o-Alkynylbenzamides and Electron-Deficient Alkenes

Youssef Madich

Youssef Madich

Departamento de Química Orgánica II, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, 48080 Bilbao, Spain

Laboratoire de Chimie Bio-Organique et Macromoléculaire, Faculté des Sciences et Techniques Marrakech, Université Cadi Ayyad, BP 549, Marrakech, Morocco

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Rosana Álvarez

Corresponding Author

Rosana Álvarez

Departamento de Química Orgánica, Facultad de Química, Universidade de Vigo, Campus As Lagoas-Marcosende, 36310 Vigo, Spain, http://webs.uvigo.es/delera/

Rosana Álvarez, Departamento de Química Orgánica, Facultad de Química, Universidade de Vigo, Campus As Lagoas-Marcosende, 36310 Vigo, Spain

José M. Aurrecoechea, Departamento de Química Orgánica II, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, 48080 Bilbao, Spain

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José M. Aurrecoechea

Corresponding Author

José M. Aurrecoechea

Departamento de Química Orgánica II, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, 48080 Bilbao, Spain

Rosana Álvarez, Departamento de Química Orgánica, Facultad de Química, Universidade de Vigo, Campus As Lagoas-Marcosende, 36310 Vigo, Spain

José M. Aurrecoechea, Departamento de Química Orgánica II, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, 48080 Bilbao, Spain

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First published: 15 August 2014
Citations: 26

Dedicated to the memory of Professor Alan R. Katritzky

Graphical Abstract

Oxycyclization/oxidative Heck cascade reactions between o-alkynylbenzamides and electron-deficient alkenes have a cyclization regiochemistry that is catalyst dependent. Thus, the 6-endo-regioselectivity reported for a PdCl2(PPh3)2 catalyst becomes a preference for 5-exo-products when Pd(OAc)2 is used.

Abstract

A Pd-catalyzed 5-exo-selective oxycyclization/oxidative Heck coupling cascade is described, starting from readily available ortho-alkynylbenzamides and functionalized olefins. The key to a high regioselectivity in the cyclization step is the choice of catalyst and/or additives. Thus, Pd(OAc)2 provides the desired 5-exo products predominantly, whereas with PdCl2 or Pd(TFA)2, the corresponding 6-endo products prevail. The subsequent oxidative Heck-type coupling takes place stereoselectively with the very predominant formation of E isomers, leading to an effective preparation of structurally diverse carbonyl-substituted allylideneisobenzofuranimines.