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A facile synthesis of various pyrazolo[1,2-a] indazoles from pyrazolidinones and propiolates via iridium(iii)-catalysed C-H bond activation/subsequent [4+1] cyclization has been developed. The reaction proceeds smoothly under mild reaction conditions and propiolates act as a novel C1 synthon. This transformation represents a redox-neutral process, exhibits a highly regioselectivity, and tolerates various functional groups.

We herein report a highly regioselective rhodium-catalyzed C6- and C7H H bond functionalization of indolines with alkynes by using 2-pyrimidine as a directing group. Moreover, NH-free benzo[g]indole unit could be obtained by an oxidation/removal of the directing group sequence.

Vinly azides are featured as electrophiles, nucleophiles, and radical acceptors in synthetic chemistry and have emerged as rapid and versatile synthons in the preparation of N-heterocyclic systems. Herein, a novel approach to 2-arylindoles via Pd(II)-catalyzed cyclization reaction of anilines with vinyl azides has been achieved, which furnishes the versatile 2-arylindoles with high efficieny and excellent regioselectivity.