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.