A Ru(II)-catalyzed facile and controllable protocol for C−H alkylation and spirocyclization of 2-arylquinoxalines with maleimides has been achieved under ambient air in high yields. Sequential ortho-C−H activation and C-annulation results in the formation of diverse polyheterocycles containing spiro[indeno[1,2b]quinoxaline-11,3′-pyrrolidine]-2′,5′-diones, which are of potent interest in medicinal chemistry. Mechanistic investigations suggest a reversible cleavage of the ortho-C−H bond in the turnover-limiting step.
The visible light-mediated C-3 alkoxylation of imidazopyridines with alcohols has been achieved using rose bengal as an organic photoredox catalyst at room temperature. Widely abundant air acts as the terminal oxidant that avoids the use of a stoichiometric amount of peroxo compounds. A wide range of functional groups could be tolerated under the reaction conditions to produce C(sp)-H alkoxylated products in high yields.
The metal‐free sodium persulfate mediated direct selenylation of arenofurans with diaryl diselenides at room temperature was developed, and the products were obtained in high yields. The reaction was found to be applicable to a variety of naphthofurans, benzofurans, and furocoumarins. To the best of our knowledge, this is the first report of the metal‐free direct selenylation of arenofurans. The experimental results suggest that the reaction proceeds through an electrophilic substitution pathway.
A general and practical
method for the direct C–H amination
of 2H-indazoles with a series of amines including
aliphatic primary amines, secondary amines, azoles, and sulfoximines
via organophotoredox-catalyzed oxidative coupling has been disclosed
at room temperature under ambient air conditions. Additionally, this
protocol is used for free aminated 2H-indazole synthesis.
A mechanistic study revealed that a single electron transfer (SET)
pathway might be involved in this reaction.
A hitherto unreported aminomethylation occurs at C-3 of imidazopyridines with morpholine in the presence of (diacetoxyiodo)benzene at ambient temperature in short reaction times. This methodology is also applicable to indolizine, imidazo[2,1-b]thiazole, benzo[d]imidazo[2,1-b]thiazole, and indole. Interestingly, the aminomethylation involving morpholine as a source of methylene group is a new phenomenon. This protocol is of much potential for the synthesis of aminomethylated derivatives under mild reaction conditions.
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