efficient protocol was developed for the synthesis of carboxylic acids, esters, and amides through oxidation of alkynyl boronates, generated directly from terminal alkynes. This protocol represents the first example of C(sp)−B bond oxidation. This approach displays a broad substrate scope, including aryl and alkyl alkynes, and exhibits excellent functionalgroup tolerance. Water, primary and secondary
Multisubstituted olefins are efficiently prepared by the zirconocene-mediated regio- and stereoselective coupling between 1-alkynylboronates and ethylene, followed by sequential transformation in moderate to high yields. The proper combination of substrates and reaction conditions is important for high yields. The synthesis of various tetrasubstituted alkenes in a regio- and stereocontrolled manner
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)
Low-Coordinate NHC–Zinc Hydride Complexes Catalyze Alkyne C–H Borylation and Hydroboration Using Pinacolborane
作者:Richard J. Procter、Marina Uzelac、Jessica Cid、Philip J. Rushworth、Michael J. Ingleson
DOI:10.1021/acscatal.9b01370
日期:2019.6.7
DFT calculations all support mechanisms involving organozinc species that undergo metathesis with HBPin. Furthermore, zinc-catalyzed hydroboration can proceed via a hydrozincation step, which does not require any exogenous catalyst in contrast to all previously reported alkyne hydrozincations. Bulky N-heterocyclic carbenes (NHCs) are key for effective catalysis as the NHCsteric bulk enhances the stability
Transfer C–H borylation is an isodesmic approach to the borylation reaction using B–C-containing molecules as boron sources. In this work, we report that 2-mercaptothiazole and other analogues are active for the metal-free borylation of heterocycles and terminalalkynes. Alkynes are challenging substrates to C–H borylate because they undergo side reactions with most borylating agents. The ability of