A highly efficient Rh(III)-catalyzed oxidative C−H/C−H cross-coupling of [1,2,4]triazolo[1,5-a]pyrimidines (TAP) with indoles and pyrroles has been developed, which provides an opportunity to rapidly assemble a large library of novel excited-state intramolecular proton transfer (ESIPT) fluorophores. The resulting 7-(pyrrol-2-yl)TAPs only show the enol-form emission, while 7-(indol-2-yl)TAPs would undergo an ESIPT process and mainly exhibit the keto-form emission. In highly polar solvents, the enol-form emission of 7-(indol-2-yl)TAPs is enhanced significantly, thus showing the dual emission of enol and keto forms.

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Disclosed herein is a rhodium-catalyzed oxidative C–H activation/domino annulation of N-Boc-anilines with 1,3-diynes for the construction of tricyclic N,O-heteroaromatics. This reaction features easily available substrates, mild reaction conditions, high regioselectivity, mono/diannulation selectivity, and intra/intermolecular annulation selectivity. Moreover, this synthetic protocol enables the rapid assembly of a library of blue-emitting molecules with high quantum yields, among of which two fluorophores with pure blue-emission in toluene are discovered.

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