Development of (quinolinyl)amido-based pincer palladium complexes: a robust and phosphine-free catalyst system for C–H arylation of benzothiazoles. (12th April 2017)

• Record Type: Journal Article
• Authors: Pandiri, Hanumanprasad; Soni, Vineeta; Gonnade, Rajesh G.; Punji, Benudhar
• Is Part Of: New journal of chemistry. Volume 41:Number 9(2017)
• Page Start: 3543
• Page End: 3554
• Publication Date: 2017-04-12
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c7nj00452d
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Well-defined (quinolinyl)amido-pincer palladium complexes are developed and employed for the catalytic C–H bond arylation of benzothiazoles with aryl iodides, which can be recycled and reused for several cycles. Abstract : (Quinolinyl)amido-ligated palladium(ii ) complexes have been synthesized and applied in the catalytic C–H bond arylation of benzothiazoles. The tridentate ligand precursors R2 N-C(O)CH2 -(NH)-C9 H6 N [( R2 NNN 8-Q )–H; R2 N = morpholinyl, Me- N -piperazinyl] and the pincer palladium complexes [κ N, κ N, κ N -{R2 N-C(O)CH2 -(μ-N)-C9 H6 N}]PdX [( R2 NNN 8-Q )PdX {R2 N = Et2 N, morpholinyl, Me- N -piperazinyl; X = OAc or Cl}] were efficiently synthesized, and characterized by various analytical techniques. The iodo derivative ( Et2 NNN 8-Q )PdI was obtained in excellent yield by the treatment of the complex ( Et2 NNN 8-Q )PdCl with KI. The molecular structures of complexes ( Et2 NNN 8-Q )Pd(OAc) (2a ), ( Et2 NNN 8-Q )PdCl (3a ) and ( Et2 NNN 8-Q )PdI (4a ) were elucidated by X-ray crystallography. Complex3a was found to be the most efficient catalyst for direct C–H bond arylation of substituted benzothiazoles with diverse aryl iodides using a mild base, K2 CO3 . The working catalyst system3a is highly robust and can be recycled and reused several times for the arylation of benzothiazole without loss of catalytic activity. Preliminary mechanistic investigations using controlled studies and kinetic analysis have been performed, which greatly support a molecular mechanism for the arylation.