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The Hiyama Cross‐Coupling Reaction at Parts Per Million Levels of Pd: In Situ Formation of Highly Active Spirosilicates in Glycol Solvents
Author(s) -
Ichii Shun,
Hamasaka Go,
Uozumi Yasuhiro
Publication year - 2019
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201901155
Subject(s) - transmetalation , chemistry , coupling reaction , aryl , reactive intermediate , ethylene glycol , aryl halide , reagent , in situ , polymer chemistry , derivatization , organic chemistry , palladium , catalysis , alkyl , high performance liquid chromatography
A palladium NNC‐pincer complex at a 5 mol ppm loading efficiently catalyzed the Hiyama coupling reaction of aryl bromides with aryl(trialkoxy)silanes in propylene glycol to give the corresponding biaryls in excellent yields. This method was applied to the syntheses of adapalene and a biaryl‐type liquid‐crystalline compound, as well as to the derivatization of dextromethorphan and norfloxacin. ESI‐MS and NMR analyses of the reaction mixture suggested the formation of pentacoordinate spirosilicate intermediates in situ. Preliminary theoretical studies revealed that the glycol‐derived silicate intermediates formed in situ are quite reactive silicon reagents in the transmetalation step.