The higher reactivity of ketenes formed from anion 2 compared to IIa becomes also evident from the reaction with trityl chloride. Albeit in this case the intermediated ketene 4 is accessible in a high yield of 96% and can be isolated in crystalline form (Figure ), it also undergoes cyclization with another equivalent of 2-Na to form cyclobutadione 5. This product can be cleanly obtained when the ketenyl anion is treated with only 0.5 equiv. of trityl chloride. Comparison of the structure parameters of 4 with the ketenyl anion, shows a considerable lengthening of the C1-C2 (from 1.205 to 1.317 Å) and a shortening of the C2-O1 bond length (from 1.191 to 1.159 Å) in the ketene reflecting the loss of the partial ynolate character found in [2•(Na(crypt)]. Cyclobutane formation is furthermore observed with the Brønsted acid, hydrogen chloride, and with 0.5 eq. of (PPh3)AuCl yielding the protonated and aurated cyclobutadiones 6 and 8. Interestingly, the reaction between 2-Na and Brookhart's acid ([H(Et2O)2][BAr F ]) showed the formation of a hydrocarbon soluble product, which could be identified as compound 7. Using 2 equivalents of acid, compound 7 was cleanly isolated in 82% as a colorless solid. Although the mechanism of the ketone formation from 2-Na is unclear, it presumably proceeds via initial attack of 2-Na at the proton-substituted ketene, with the intermediate formed being intercepted from cyclization by protonation, with subsequent loss of one molecule CO. Overall, these reactions clearly show that the ketenyl anion 2 despite the highly electron-withdrawing tosyl group favors reaction at C1 carbon atom. Differences to the thus far reported ketenyl anions presumably arise from the reduced steric demand of 2, which results in the facile reaction of the formed ketene with the ketenyl anion, thus giving access to differently substituted cyclobutadiones.