α‐Oxygen‐Substituted Organolithium Compounds and their Carbenoid Nature: Reactions with RLi and Other Nucleophiles, Experimental and IGLO‐Calculated ¹³C‐NMR Shifts of the Carbenoid C Atom

In addition to the earlier [1] demonstrated C–O bond elongation between the anionic carbon atom and oxygen in α‐lithiated ethers which indicates a carbenoid character of these compounds we provide further evidence for this property in this publication. Thus, α‐lithiated ethers RCH(Li)–OR' react as electrophiles with nucleophiles R' Li to give RCH(Li)–R' + LiOR', and the 13 C‐NMR signal of the carbenoid C atom is shifted downfield (compared to the 13 C signal of the corresponding non‐lithiated compound). Since the latter two observations are also made in the Li/ Hal carbenoid series, α‐lithiated ethers indeed are Li/oxygen carbenoids. Furthermore, for the first time we have calculated the 13 C shifts of carbenoid C atoms in the Li/oxygen carbenoid series by means of the IGLO method: the calculated data agree nicely with the experimental ones. They even allow the preferred bridged structure in solution to be determined.