Unlocking Free α-Trifluoromethoxy Carbene Reactivity from Aldehyde.

Carbenes, recognized as potent intermediates, enable otherwise inaccessible chemical transformations. The development of readily accessible aldehydes as oxycarbene precursors is of significant research value, yet it has never been achieved before. Compounds with a better decomposable trifluoromethoxy (-OCF3) group have found diverse applications in pharmaceutical and agricultural research and are considered promising PFAS's alternatives. Here, we report that (hetero)aryl-, alkenyl-, and alkynyl-aldehydes are readily converted (via isolable or in situ-utilized α-OCF3 secondary chlorides derived from O-trifluoromethylation/chlorination of aldehydes) to unprecedented, structurally diverse free α-OCF3 carbenes to facilitate three reaction classes, including cyclopropanation, Si-H insertion, and phosphonylation via phosphorus ylide. This approach opens avenues to access previously elusive but potentially valuable OCF3-containing compounds, including OCF3-substituted cyclopropanes, silanes, and phosphonates, expanding both organofluorine and carbene chemistry.