Li_2024_Science_383_498

The Pauson-Khand reaction has in the past 50 years become one of the most common cycloaddition reactions in chemistry. Coupling two unsaturated bonds with carbon monoxide, the transformation remains limited to CO as a C(1) building block. Herein we report analogous cycloaddition reactions with nitrenes as an N(1) unit. The reaction of a nonconjugated diene with a nitrene precursor produces bicyclic bioisosteres of common saturated heterocycles such as piperidine, morpholine, and piperazine. Experimental and computational mechanistic studies support relaying of the diradical nature of triplet nitrene into the Pi-system. We showcase the reaction's utility in late-stage functionalization of drug compounds and discovery of soluble epoxide hydrolase inhibitors.