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Sonogashira Cross-Coupling of Aryl Ammonium Salts by Selective C-N Activation Catalyzed by Air- and Moisture-Stable, Highly Active [Pd(NHC)(3-CF3-An)Cl2] (An = Aniline) Precatalysts

Peng Lei*, Yibo Wang, Caixia Zhang, Yuge Hu, Juntao Feng, Zhiqing Ma*, Xili Liu*, Roman Szostak and Michal Szostak*

*Northwest A&F University, Yangling, Shaanxi 712100, China; Rutgers University, Newark, New Jersey 07102, USA, Email: peng.leinwafu.edu.cn, mazhiqing2000126.com, seedlingnwafu.edu.cn, michal.szostakrutgers.edu

P. Lei, Y. Wang, C. Zhang, X. Hu, J. Feng, Z. Ma, X. Liu, R. Szostak, M. Szostak, Org. Lett., 2022, 24, 6310-6315.

DOI: 10.1021/acs.orglett.2c02534


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Abstract

Air- and moisture-stable [Pd(IPr)(3-CF3-An)Cl2] (An = aniline) catalyzes a Sonogashira cross-coupling of aryl ammonium salts. This reaction offers broad scope and excellent C-N activation selectivity in the challenging alkynylative cross-coupling of aryl ammonium salts.

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General Procedure for the Sonogashira Cross-Coupling of Aryltrimethylammonium Salts

An oven-dried vial equipped with a stir bar was charged with an aryltrimethylammonium salt substrate (neat, 1.0 equiv), t-BuONa (typically, 2.0 equiv), Pd-NHC catalyst (typically, 10 mol%), placed under a positive pressure of argon, and subjected to three evacuation/backfilling cycles under high vacuum. Alkyne (typically, 1.0 equiv) and THF (typically, 0.2 M) was added with vigorous stirring at room temperature, the reaction mixture was placed in a preheated oil bath at 45 C and stirred for the indicated time. After the indicated time, the reaction mixture was cooled down to room temperature, diluted with EtOAc (10 mL), filtered, and concentrated. The sample was analyzed by 1H NMR (CDCl3, 500 MHz) and GC-MS to obtain conversion, selectivity and yield using internal standard and comparison with authentic samples. Purification by chromatography on silica gel (EtOAc/petroleum ether) afforded the title product.


Key Words

Sonogashira coupling, alkynylation


ID: J54-Y2022