The potential of copper(I)-zeolite catalysis was evaluated in the three-component KA 2 -coupling mediated synthesis of α-tertiary propargylamines. Our archetypal copper(I)-doped zeolite Cu I -USY proved to be efficient under ligand-and solvent-free conditions at 80 °C. Usable up to four times, this catalytic material enables the coupling of diverse ketones, alkynes, and amines with a broad functional group tolerance. A decarboxylative and a desilylative version, respectively, involving an alkynoic acid and trimethylsilylacetylene as alkyne surrogates, was also set up to bypass selectivity issues and/or to access α-tertiary propargylamines that are unattainable under standard KA 2 conditions. Interestingly, the KA 2 -type coupling reactions were successfully linked to other Cu I -catalyzed reactions, thus resulting in sequential one-pot processes under full Cu I -USY catalysis.
Herein, we describe a rapid microwave‐assisted, metal‐free synthesis of substituted quinoxalinones and quinoxalines using the carbene‐mediated reaction between aryldiazo esters and 1,2‐diamines. The reaction can encompass a range of substituents and structural variations to afford quinoxalin‐2‐ones in 14–80 % yield and corresponding quinoxalines in good to excellent yields upon oxidation (67–96 %). The approach can be employed to generate symmetrical and unsymmetrical 2,3‐diarylquinoxalines, bis‐quinoxalines as well as novel quinoxaline‐substituted diazo esters and should be a valuable addition to the heterocycle synthesis toolbox.
A series of ethynylpyridine-appended nucleobases have been designed, synthesized, characterized and employed for the formation of crystalline molecular networks by hydrogen/coordination bonding.
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