Pyramidalization and reactivity of trigonal centers. X-ray crystal structure analysis of two silyl enol ethers from 1-benzoyl- and 1-(methoxycarbonyl)-2-tert-butyl-3,5-dimethyl-4-imidazolidinone (reagents for amino acid synthesis)
摘要:
The title structures, which may be considered models for the Li enolates, contain three trigonal centers (N1, N3, C5) with unusually large pyramidalization. This leads to an all-trans arrangement of four substituents with respect to the plane of the five-membered ring which is in a flat twist conformation, bearing the tert-butyl group in a quasi-axial-type position. The pyramidalization on C5 is in the same direction from which this carbon undergoes electrophilic attack in reactions of the corresponding Li enolates.