Omkar Revu, Maksim Vasilev, Praveen Gajula, Nageswara Rao Kalikinidi, Madhusudhan Reddy Gadi, Huiping Zhao, Shanika M. P. Gamage, Graham Hibbert, Ongolu Ravikumar, Lalitha Gummidi, Venkatarathnam Nasipireddy, Arun Vinodini, Jonathan Bietsch, Zhirui Wang, Jack D. Brown, Gopal Sirasani, Joseph D. Armstrong, III, Aravind S. Gangu, Bo Qu, Chris H. Senanayake
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Development of a Safer Continuous Flow Process for B2(OH)4-Mediated Chemoselective Reduction of Nitroarenes to Anilines
Tetrahydroxydiboron [B2(OH)4] is a chemoselective reducing reagent for nitro reductions in the presence of other labile functional groups. However, there are significant process safety challenges associated with the application of this reducing reagent, including rapid heat release and thermal instability of B2(OH)4 in aprotic polar solvents. Herein, we report the development of a safer continuous flow process applying B2(OH)4-mediated chemoselective nitro reduction conditions. The safety challenges were addressed by employing continuous flow technology along with identifying a suitable protic cosolvent EtOH. Functional group tolerance toward cyano groups, halides, carboxylic acids, olefins, imines, and benzylic alcohols was demonstrated in flow with higher reaction yield compared to that in batch synthesis. The modified reaction conditions provide a potentially scalable approach to widespread applications of this key transformation for the generation of highly functionalized diversified aniline derivatives.
期刊介绍:
The journal Organic Process Research & Development serves as a communication tool between industrial chemists and chemists working in universities and research institutes. As such, it reports original work from the broad field of industrial process chemistry but also presents academic results that are relevant, or potentially relevant, to industrial applications. Process chemistry is the science that enables the safe, environmentally benign and ultimately economical manufacturing of organic compounds that are required in larger amounts to help address the needs of society. Consequently, the Journal encompasses every aspect of organic chemistry, including all aspects of catalysis, synthetic methodology development and synthetic strategy exploration, but also includes aspects from analytical and solid-state chemistry and chemical engineering, such as work-up tools,process safety, or flow-chemistry. The goal of development and optimization of chemical reactions and processes is their transfer to a larger scale; original work describing such studies and the actual implementation on scale is highly relevant to the journal. However, studies on new developments from either industry, research institutes or academia that have not yet been demonstrated on scale, but where an industrial utility can be expected and where the study has addressed important prerequisites for a scale-up and has given confidence into the reliability and practicality of the chemistry, also serve the mission of OPR&D as a communication tool between the different contributors to the field.