Silver Catalyzed Bromination of Aromatics with N -bromosuccinimide
- PDF / 489,872 Bytes
- 6 Pages / 595.276 x 790.866 pts Page_size
- 53 Downloads / 133 Views
Silver Catalyzed Bromination of Aromatics with N-bromosuccinimide Rui Zhang • Lei Huang • Yanfang Zhang • Xiaorong Chen • Weihong Xing • Jun Huang
Received: 14 November 2011 / Accepted: 28 December 2011 / Published online: 10 January 2012 Ó Springer Science+Business Media, LLC 2012
Abstract A heterogeneous silver catalyst was prepared and applied efficiently for the selective bromination of aromatics with NBS. The silver nanoparticles combined with the acidic support HMB can activate both the aromatic ring and NBS, and the synergistic effects between the silver nanoparticles and the HMB highly enhanced the efficiency of the bromination reaction. Keywords Silver Aryl bromides Bromination Aromatics N-bromosuccinimide
1 Introduction Aryl bromides are useful intermediates for the synthesis of pharmaceuticals, agrochemicals and functional materials through cross-coupling reactions [1–4]. A variety of brominating agents have been developed and reported for the bromination of aromatic compounds [5, 6]. Among these reagents, N-bromosuccinimide (NBS) is a useful brominating reagent in laboratory synthesis, since only inert succinimide by-product formed in the process. A lot of methods have been developed for the preparation of aryl bromides from electron-rich aromatics, but the bromination of unactivated aromatics with NBS proceeded only in the presence of stoichiometric amounts of strong Lewis acids or protic acids as catalysts [7–10]. Moreover, harsh experimental conditions were required for the bromination
R. Zhang L. Huang Y. Zhang X. Chen W. Xing J. Huang (&) State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China e-mail: [email protected]
123
of deactivated aromatics, such as high temperature and high acidic solutions [11, 12]. Recently, efficient catalyst systems were reported for the bromination reactions under mild conditions, but high catalyst loading required, and only electron-rich aromatics were applicable [13–17]. Thereafter, the development of green and efficient catalysts for the bromination of aromatics remains important. Mesoporous molecular sieves are versatile catalysts and catalytic supports as they are thermal stable, strong acidic, with high surface area and large pore volume, which are highly beneficial to catalytic reactions [18–21]. For example, Kumar et al. [22] reported a mesoporous catalyst Ag-MCM-41 applied for ozone decomposition at ambient temperature. In addition, a SBA-15 supported silver nanocatalyst was developed for the three-component reaction of aldehydes, alkynes and amines [23]. Herein, we reported a silver nanocatalyst on mesoporous beta molecular sieve (Ag/HMB) for the selective bromination of aromatics with NBS, and the catalyst was efficient and reusable (Scheme 1).
2 Experimental 2.1 Reagents All the reagents were purchased from Aladdin Reagent, Sigma-Aldrich Company and Alfa-Aesar Company without further purification. 2.2 Analytical Methods G
Data Loading...
