3-Component reactions for accessing heterocycle-rich topologies: trapping of pyrrole-stabilized carbenes via net bimolecular C–H or N–H insertion

The intermolecular trapping of free carbenes derived from diazo precursors is well documented in the literature. We have recently reported the generation of free carbenes derived from 2-alkynyliminoheterocycles, a process that is both 100% atom economical and metal free. Here, we expand the synthetic utility of heteroaryl-stabilized, free carbenes by demonstrating a host of intermolecular third-component trapping reactions. Terminal alkynes, N-Boc carbamates, and NH-amides are shown to be suitable third-component traps. Strategic selection of the three reaction partners (i.e., the 2-alkynyliminoheterocycle, the electron-deficient alkyne partner, and the trapping moiety) enables access to product diversity of variable topology and a high degree of heterocycle incorporation.