Abstractα‐Metallated ylides have recently been reported to undergo phosphine by CO exchange at the ylidic carbon atom to form isolable ketenyl anions. Systematic studies on the tosyl‐substituted yldiides, R3P=C(M)Ts (M=Li, Na, K), now reveal that carbonylation may lead to a competing metal salt (MTs) elimination. This side‐reaction can be controlled by the choice of phosphine, metal cation, solvent and co‐ligands, thus enabling the selective isolation of the ketenyl anion [Ts−CCO]M (2‐M). Complexation of 2‐Na by crown ether or cryptand allowed structure elucidation of the first free ketenyl anion [Ts−CCO]−, which showed an almost linear Ts−C−C linkage indicative for a pronounced ynolate character. However, DFT studies support a high charge at the ketenyl carbon atom, which is reflected in the selective carbon‐centered reactivity. Overall, the present study provides important information on the selectivity control of ketenyl anion formation which will be crucial for future applications.
摘要α-金属化的酰化物最近被报道通过在酰碳原子上进行 CO 交换来形成可分离的酮阴离子。对 R3P=C(M)Ts (M=Li、Na、K) 的对甲苯基取代的乙二酰胺的系统研究表明,羰基化可能会导致金属盐(MTs)的竞争性消除。这种副反应可以通过选择膦、金属阳离子、溶剂和共配位体来控制,从而能够选择性地分离出酮阴离子 [Ts-CCO]M (2-M)。2-Na 与冠醚或隐色体络合后,第一个游离的酮阴离子 [Ts-CCO]- 的结构得以阐明,该阴离子显示出几乎线性的 Ts-C-C 连接,表明其具有明显的炔酸特性。然而,DFT 研究支持在酮基碳原子上存在高电荷,这反映在选择性碳中心反应活性上。总之,本研究为控制酮基阴离子形成的选择性提供了重要信息,这对未来的应用至关重要。