The Rh(III)-catalyzed
regioselective C–H amidation of N-methoxy-1H-indole-1-carboxamides by 1,4,2-dioxazol-5-ones
was studied. N-Methoxy amide, the directing group
(DG) of interest, undergoes four different transformations through
DG-retained, -coupled, -eliminated, or -migrated processes under moderately
varied reaction conditions. Solvents, additives, and temperature play
important roles in these selective transformations; a trace addition
of water favors the functional group (FG)-assisted DG elimination;
extra addition of KHSO4 greatly enhances the formation of the DG-coupled product;
high-temperature and proper FG together can shift the position of
DG through intermolecular Friedel–Crafts-like acylation. The
catalytic mechanisms underlying these reactions were further investigated
through density functional theory calculations and experimental studies
including the characterization of amido-inserted rhodacycle. An overall
catalytic pathway was proposed to illustrate the reactions involved
in the regioselective amidation of N-methoxy-1H-indole-1-carboxamide.
Rhodium-catalyzed cascade reactions of benzoic acids with 1,4,2-dioxazol-5-ones afford 2,5-substituted benzoxazinones, which exhibited AIE properties with an ESIPT phenomenon.
Transition metal-catalysed C−H bond functionalisations have been extensively developed in organic and medicinal chemistry. Among these catalytic approaches, the selective activation of C(sp3)−H and C(sp2)−H bonds is particularly appealing for...
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