The synthesis of functionalized carbazoles as privileged nitrogen heterocycles has emerged as a central topic in drug discovery and material science. We herein disclose the Rhodium(III)-catalyzed cross-coupling reaction between indolyl nitrones and 2-methylidene cyclic carbonate as an allylating surrogate, resulting in the formation of C2-formylated carbazoles via tandem C−H allylation, [3+2] cycloaddition, aromatization and benzylic oxidation. The synthetic utility of this protocol is highlighted by a variety of post-transformation of C2-formylated carbazoles.