Metal-Dependent Umpolung Reactivity of Carbenes Derived from Cyclopropenes

Metal carbenes, divalent carbon species, are versatile intermediates that enable novel synthetic pathways. These species exhibit either electrophilic or nucleophilic character, depending on the carbene and metal fragments. Although the metal carbene reactivity is regulated by the metal, the umpolung of carbene reactivity by changing metal remains challenging. Here, we report a unique metal-induced de novo umpolung of carbene reactivity, wherein a carbene precursor can be transformed into either an electrophilic carbene or a nucleophilic carbenoid, depending on the metal promoters. Thus, a chemodivergent reaction of isatins and cyclopropenes is developed. Under the promotion of Zn2+ halides, a nucleophilic zinc carbenoid is formed and trapped by isatins to produce oxindole derivatives containing an alkenyl halide moiety. Using Rh-2(esp)(2) as a catalyst, the reaction delivers oxindoles carrying a dihydrofuran unit. This work provides a facile approach to harness the metal carbene reactivity and is critical for the development of diversity-oriented synthesis.