We report two viable routes for the 1,2-difunctionalization of aminoalkynes using only oxidants. In the presence of a gold catalyst, nitrones enable the oxoamination of aminoalkynes 1 to form 2-aminoamides 2. With a suitable gold catalyst, nitrosobenzenes implement an alkyne/nitroso metathesis of the same substrates to give 2-oxoiminylamides 3. These two novel oxidations also provide 1,2-aminoalcohols with opposite regioselectivity via NaBH(4) reduction in situ.
Reported herein is the novel gold-catalyzed intermolecular [2+2+2] cycloaddition of ynamides with two discrete nitriles to form monomeric 4-aminopyrimidines, which are pharmaceutically important structural motifs. The utility of this new cycloaddition is demonstrated by the excellent regioselectivity obtained using a variety of ynamides and nitriles.
Enantioselective nickel‐catalyzed arylative cyclizations of substrates containing a Z‐allylic phosphate tethered to an alkyne are described. These reactions give multisubstituted chiral aza‐ and carbocycles, and are initiated by the addition of an arylboronic acid to the alkyne, followed by cyclization of the resulting alkenylnickel species onto the allylic phosphate. The reversible E/Z isomerization of the alkenylnickel species is essential for the success of the reactions.
The enantioselective synthesis of highly functionalized chiral cyclopent-2-enones by the reaction of alkynyl malonate esters with arylboronic acids is described. These desymmetrizing arylative cyclizations are catalyzed by a chiral phosphinooxazoline/nickel complex, and cyclization is enabled by the reversible E/Z isomerization of alkenylnickel species. The general methodology is also applicable to the synthesis of 1,6-dihydropyridin-3(2H)-ones.
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