Benzylation of arenes with benzyl halides synergistically promoted by in situ generated superacid boron trifluoride monohydrate and tetrahaloboric acid
To examine the assembly methodology of diarylmethanes, a benzylation of (hetero)arenes with benzyl halides has been developed and various diarylmethanes were furnished with yields of up to 98% and regioselectivities of up to >99%. The complexation of the by-product halogen hydride with BF3·OEt2 generated the Bronsted acid BF3·HX (HBF3X, X=Cl or Br) in situ to synergistically promote the benzylation.
Huang, Ruofeng,Zhang, Xiaohui,Pan, Jing,Li, Jiaqiang,Shen, Hang,Ling, Xuege,Xiong, Yan
supporting information
p. 1540 - 1546
(2015/03/04)
Superacid BF3-H2O promoted benzylation of arenes with benzyl alcohols and acetates initiated by trace water
A convenient procedure employing simple starting materials benzyl alcohols and acetates as the benzyl donors to assemble a series of diarylalkanes through benzylation of arenes using in situ prepared superacid BF3-H 2O as an efficient promoter has been developed. The beneficial role of water in the reaction has been clarified with combination of control experiments and 11B NMR analysis. This reaction is a self-promoted model, which is triggered by the trace of water and continuously promoted by self released by-product water (or carboxylic acid). A wide range of substrates are investigated and the moderate to excellent yields and the good regioselectivities for secondary benzyl alcohols as well as arenes bearing electron-withdrawing groups have been achieved. As a result, moisture in the reaction system has been utilized as an efficient initiator in all benzylation cases.
Zhang, Shuting,Zhang, Xiaohui,Ling, Xuege,He, Chao,Huang, Ruofeng,Pan, Jing,Li, Jiaqiang,Xiong, Yan
p. 30768 - 30774
(2014/08/05)
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