An alcohol-directed, nickel-catalyzed
three-component umpolung
carboamination of unactivated alkenes with aryl/alkenylboronic esters
and electrophilic aminating reagents is reported. This transformation
is enabled by specifically tailored O-(2,6-dimethoxybenzoyl)hydroxylamine
electrophiles that suppress competitive processes, including undesired
β-hydride elimination and transesterification between the alcohol
substrate and electrophile. The reaction delivers the desired 1,2-carboaminated
products with generally high regio- and syn-diastereoselectivity
and exhibits a broad scope of coupling partners and alkenes, including
complex natural products. Various mechanistic experiments and analysis
of the stereochemical outcome with a cyclic alkene substrate, as confirmed
by X-ray crystallographic analysis, support alcohol-directed syn-insertion of an organonickel(I) species.
Regioselective hydrofunctionalization of alkynes represents a straightforward route to access alkenyl boronate and silane building blocks. In previously reported catalytic systems, high selectivity is achieved with a limited scope of substrates and/or reagents, with general solutions lacking. Herein, we describe a selective copper-catalyzed Markovnikov hydrofunctionalization of terminal alkynes that is facilitated by strongly donating cyclic (alkyl)(amino)carbene (CAAC) ligands. Using this method, both alkyl-and aryl-substituted alkynes are coupled with a variety of boryl and silyl reagents with high α-selectivity. The reaction is scalable, and the products are versatile intermediates that can participate in various downstream transformations.Preliminary mechanistic experiments shed light on the role of CAAC ligands in this process. File list (2) download file view on ChemRxiv Manuscript.pdf (2.91 MiB) download file view on ChemRxiv Supporting Info.pdf (7.13 MiB)
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