Size-Driven Inversion of Selectivity in Esterification Reactions: Secondary Beat Primary Alcohols
作者:Stefanie Mayr、Marta Marin-Luna、Hendrik Zipse
DOI:10.1021/acs.joc.0c02848
日期:2021.2.19
alcohols carrying large aromatic side chains with anhydrides differing in size and electronic structure have been measured. While primary alcohols react faster than secondary ones in transformations with monosubstituted benzoic anhydridederivatives, relative reactivities are inverted in reactions with sterically biased 1-naphthyl anhydrides. Further analysis of reaction rates shows that increasing substrate
alkylation, and trifluoromethanesulfonic acid (triflic acid, TfOH) was also a good catalyst. The catalytic activity of metal triflates and TfOH increased in the order La(OTf)3 < Yb(OTf)3 < TfOH < Sc(OTf)3 < Hf(OTf)4. A mechanistic study was also performed. The reaction of 1-phenylethanol (4a) in the presence of Sc(OTf)3 in nitromethane gave an equilibrium mixture of 4a and bis(1-phenylethyl) ether (54). Addition
Herein, we report a distinctive photoredox/copper dual-catalyzed esterification of benzylic C–H bonds through the combination of photoredox-mediated hydrogen atom transfer and Cu(II)-mediated radical-polar crossover. This methodology demonstrates a high functional group tolerance (>40 examples) and moderate to good yields with structurally diverse benzylic C–H substrates. Notably, stoichiometric amounts