The asymmetric construction of vicinal quaternary carbon stereocenters with at least one moiety in acyclic systems is a formidable challenge. We disclose a solution involving diastereo‐ and enantioselective oxidative 1,6‐conjugate addition. The practical asymmetric cross‐dehydrogenative coupling of 2,2‐diarylacetonitriles and diverse α‐substituted cyclic 1,3‐dicarbonyls proceeds, for vicinal quaternary carbon stereocenters with one center in acyclic systems, in excellent yields and stereoselectivities. The generality of the approach is further demonstrated by the stereoselective creation of vicinal quaternary carbon stereocenters with both centers in acyclic systems using acyclic β‐ketoesters as coupling partners. Computational studies elucidate the origins of both diastereo‐ and enantioselectivity.
We herein report the direct reaction of ynamides with 2H‐tetrazoles under metal‐free conditions to provide a variety of functionalized (Z)‐α‐tetrazole enamide products in high yields, including the N‐2 and N‐1 adducts that are easily separated. The reaction proceeds via a key keteniminium ion intermediate, generated in situ from ynamides with acidic 2H‐tetrazoles, leading to the formation of C‐N bonds efficiently. The present reaction features simple experimental operations and mild reaction conditions, high chemo‐, regio‐, and stereoselectivities, and high reaction efficiencies. Without using any catalyst, the reaction protocol should facilitate the modification of tetrazole‐containing molecules for the discovery of new potentially bioactive compounds.
A one-pot deracemization of β,γ-alkynyl α-amino esters consisting of an aerobic oxidation and chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation has been described.
A gold‐catalyzed reaction of 2H‐tetrazoles with alkynes was described for the efficient synthesis of a variety of N‐alkenylated tetrazole derivatives, including N‐1 and N‐2 vinyl functionalized products which are readily isolated by column chromatography. The reaction mechanism was proposed to be a nucleophilic addition process to the alkyne motif activated by gold catalyst. The reaction features mild reaction condition, simple operation and high yields.
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