Facile access to libraries of diversely substituted 2-aryl-benzoxazoles/benzothiazoles from readily accessible aldimines via cyclization/cross coupling in imidazolium-ILs with Pd(OAc)2 or NiCl2 (dppp) as catalyst. Issue 6 (6th February 2020)

• Record Type: Journal Article
• Authors: Malunavar, Shruti S.; Sutar, Suraj M.; Savanur, Hemantkumar M.; Kalkhambkar, Rajesh G.; Laali, Kenneth K.
• Is Part Of: Tetrahedron letters. Volume 61:Issue 6(2020)
• Publication Date: 2020-02-06
• Subjects: 2-Arylbenzoxazole/benzothiazole -- Aldimine -- Cyclization/cross-coupling -- Ionic liquids; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tetlet.2019.151509
• Languages: English
• ISSNs: 0040-4039

Abstract

Graphical abstract: Highlights: Libraries of diversely substituted 2-aryl-/heteroaryl-benzoxazoles/benzothiazoles from readily available aldimines. Two-step process of cyclization and cross-coupling. Catalysis by either Pd or Ni. One-pot sequential process. Ionic liquids as solvent with recycling/reuse potential. Abstract: A two-step protocol involving Pd-catalyzed cyclization of readily accessible p -bromophenyl-aldimines to 2-bromophenyl-benzoxazole/benzothiazole in [BMIM][PF6 ] or [BMIM][BF4 ] as solvent, followed by the Suzuki, Heck, and Sonogashira cross-coupling reactions catalyzed by Pd or Ni is described that generates libraries of diversely substituted 2-aryl-/heteroaryl-benzoxazoles/benzothiazoles in respectable isolated yields under mild reaction conditions. The feasibility to perform the two-steps in sequence in one-pot starting from the aldimines is also demonstrated and the potential for recycling/reuse of the IL solvent is also shown.