Transition metal–free ketene formation from carbon monoxide through isolable ketenyl anions

The capacity of transition metals to bind and transform carbon monoxide (CO) is critical to its use in many chemical processes as a sustainable, inexpensive C1 building block. By contrast, only few s- and p-block element compounds bind and activate CO, and conversion of CO into useful carbonyl-containing organic compounds in such cases remains elusive. We report that metalated phosphorus ylides provide facile access to ketenyl anions ([RC=C=O]–) by phosphine displacement with CO. These anions are very stable and storable reagents with a distinctive electronic structure between that of the prototypical ketene (H2C=C=O) and that of ethynol (HC≡C–OH). Nonetheless, the ketenyl anions selectively react with a range of electrophiles at the carbon atom, thus offering high-yielding and versatile access to ketenes and related compounds. Description Ketenes from ylides Most chemical reactions that build complex molecules from carbon monoxide rely on transition metal catalysis. Jörges et al. found that carbon monoxide also reacts cleanly with potassium ylides by phosphine displacement. The resulting negatively charged ketenyl compounds could be isolated and crystallographically characterized, manifesting a bent structure poised for downstream reactivity at the carbon rather than oxygen site. This behavior was borne out in a variety of reactions of the anions with electrophiles to produce ketenes and their derivatives. —JSY Metalated ylides react with carbon monoxide by phosphine displacement to form stable precursors to ketenes and related compounds.