Investigation of the scope of a [3+2] cycloaddition approach to isoxazole boronic esters
摘要:
The [3 + 2] cycloaddition reaction of nitrile oxides and alkynylboronates provides direct access to a wide variety of isoxazole boronic esters. Specifically, this technique has been employed to generate trisubstituted isoxazole 4-boronates and disubstituted isoxazoles where the boronic ester moiety can be installed at C-4 or C-5 with high levels of regiocontrol. The application of this methodology in the synthesis of non-steroidal antiinflammatory agents is also described. (c) 2005 Elsevier Ltd. All rights reserved.
作者:Dominic R. Willcox、Daniel M. De Rosa、Jack Howley、Abigail Levy、Alan Steven、Gary S. Nichol、Carole A. Morrison、Michael J. Cowley、Stephen P. Thomas
DOI:10.1002/anie.202106216
日期:2021.9.13
reactivity at the aluminium hydride centre, switching off hydroalumination and instead enabling selective reactions at the alkyne C−H σ-bond. Chemoselective C−H borylation was observed across a series of aryl- and alkyl-substituted alkynes (21 examples). On the basis of kinetic and density functional theory studies, a mechanism in which C−H borylation proceeds by σ-bondmetathesis between pinacolborane (HBpin)