1. Conformations of highly hindered aryl ethers—XVIII
2. Conformational isomers with energy barriers between them of less thanca.20 kcal/mol are typically inseparable under normal conditions; see reference 3 and (a) Lowry, T. H.; Richardson, K. S.Mechanism and Theory in Organic Chemistry, 2nd ed.; Harper & Row: New York, 1981; pp 115−130. (b) Gilman, N. W.; Rosen, P.; Earley, J. V.; Cook, C.; Todaro, L. J.J. Am. Chem. Soc.1990,112, 3969−3978 and references cited therein.
3. New synthetic route to unsymmetrically substituted pentacoordinated phosphorus. Hydrolytically stable chiral, monocyclic oxyphosphoranes