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Continuous Flow Photochemical Benzylic Bromination of a Key Intermediate in the Synthesis of a 2‐Oxazolidinone
Author(s) -
Chen Yuesu,
de Frutos Oscar,
Mateos Carlos,
Rincon Juan A.,
Cantillo David,
Kappe C. Oliver
Publication year - 2018
Publication title -
chemphotochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.13
H-Index - 18
ISSN - 2367-0932
DOI - 10.1002/cptc.201800114
Subject(s) - halogenation , continuous flow , flow chemistry , chemistry , combinatorial chemistry , organic chemistry , catalysis , physics , mechanics
A continuous flow procedure for the benzylic photobromination of methyl N,N ‐bis ( tert ‐butoxycarbonyl) phenylalaninate is presented. This photochemical transformation generating the brominated intermediate is the critical step in the synthesis of the oxazolidinone methyl (4 S ,5 R )‐3‐ N ‐ tert ‐Butoxycarbonyl‐5‐phenyl‐1,3‐oxazolidin‐2‐oxo‐4‐carboxylate, a key intermediate for the preparation of active pharmaceutical ingredients. The reaction was optimized in three continuous flow photoreactors: A self‐made reactor based on a T5 8 W black light lamp, as well as the commercially available VapourTec® UV‐150 and Corning® Advanced‐Flow™ reactors, both equipped with LED light sources. Under optimal conditions, concentrated solutions (95 g/L) of the starting material could be processed on a multi‐gram scale, providing high conversion (96 %) within 7 min at 30 °C, using 2 equivalents of N ‐bromosuccinimide (NBS).