Ni-Catalyzed regio- and stereoselective addition of arylboronic acids to terminal alkynes with a directing group tether

Abstract

Addition of arylboronic acids to directing group tethered acetylenes in a regio and stereoselective manner using an inexpensive catalytic system is achieved for the first time to access highly sought after allyl/homoallyl alcohol/amine units. The apparent vinylnickel intermediate was successfully trapped by the Michael electrophiles to get defined tri- and tetra-substituted olefins. An interesting selectivity switch was observed with internal alkynes.

Precatalyst‐Enabled Selectivity: Enantioselective NiH‐Catalyzed anti‐Hydrometalative Cyclization of Alkynones to Endo‐ and Heterocyclic Allylic Alcohols

“…Then reversible cis / trans isomerization provides E ‐alkenylnickel trans ‐ III followed by coordination of ketone to the nickel center and an intramolecular addition affording the allylic alkoxide nickel IV . Although the isomerization of cis ‐ III to trans ‐ III is sterically less favored, the coordination/addition step probably is the driving force of this reaction [4d] . Finally, the nickel species II is regenerated in the presence of H 2 O and silane [23] .…”

A Highly Efficient Dimeric Manganese‐Catalyzed Selective Hydroarylation of Internal Alkynes

“…Arylboronic acids are commercially abundant and easy to handle reagents, which recently have gained considerable momentum in selective hydroarylation of alkynes . For example, after much research with palladium, rhodium, copper, and nickel catalysts, it is recognized that the utilization of electronic and directing group strategy can normally control the regioselectivity of hydroarylation but the inherent high reactivity of these metals towards a wide range of useful functional groups simultaneously compromises their chemoselectivities (Scheme a). On the other hand, it requires several steps to install and remove the directing group before and after reactions.…”

“…For example, with Pd(Ph 3 P) 4 as catalyst, the formation of allene 4 or biaryl 5 byproducts is facilitated . Under the reaction conditions reported by Reddy et al., the use of a 10 mol % Ni(acac) 2 /Ph 3 P catalytic combination leads to a complex reaction with only a moderate yield (51 %) of the desired product along with byproducts ( 4 ). Comparison of these results using other transition metal catalysts further highlights the unique reactivity of the manganese catalysts.…”

Regioselective Access to 3-Aryl-1-aminoisoquinolines via Nickel(I)-Catalyzed C–C and C–N Cascade Coupling Reactions from the Substituted 2-(Cyanomethyl)benzonitriles

“…Based on the results above, a plausible mechanism is shown in Scheme . At the starting point, ArNi­(I)­Ln complex A was formed via the same mechanism as in previous articles. , Then Ni­(I) complex A coordinated to the C­(sp 3 )-cyano group as a regioselective preference (complex B ). After that, the aryl group on complex B was inserted into the cyano group to form Ni­(I)-ketimine complex C .…”