Synthesis and structures of alpha-lithiated vinyl ethers

The structures of alpha-lithiated vinyl ethers were explored on the basis of a combined computational and NMR study. Calculations (M06/6-31 + G(d)) on free energies of aggregate formation for a series of alpha-lithiated vinyl ethers indicated that the tetramer is generated preferentially in both the gas phase and THF solution, except for cyclohexylidene derivatives. (1-(Methoxymethoxy)vinyl)lithium, (2,2-difluoro-1-(methoxymethoxy)vinyl)lithium, and (1-butoxyvinyl)lithium were prepared in NMR tubes by the deprotonation of alkyl/alkoxylalkyl vinyl ethers or by the transmetalation of tin compounds. The NMR spectra of these lithium species in THF solution showed that in each species one aggregate is primarily present at 173 K, which is consistent with the preference of the tetramer. (C) 2018 Elsevier Ltd. All rights reserved.