Synthesis of, and Structural Assignments to the Stereoisomers of Bis (2,2‘)- and Tris (2,2‘,2‘ ‘)-Tetrahydrofurans: Conformational Features and Ionic Binding Capacities of These Gateway Polycyclic Networks

Construction of the polytetrahydrofuranyl building blocks 6−10 from the common bissiloxyacetone
precursor 11 is detailed. The approach is concise and, for the bis-(THF) pair, capitalizes on the full
retention of configuration observed during the rhodium-promoted decarbonylation of aldehydes 18 and
19. The capability of the title compounds to associate with alkali metal ions in solution and the gas
phase has demonstrated a preference for Li+ over Na+ and K+ in all cases, with 6 and 7 exhibiting
somewhat higher binding selectivities than 8−10. The relative energy orderings of attainable conformations
with the bis-THF and tris-THF series were explored computationally. The various envelope arrangements
present in the individual THF units are shown to play a significant role alongside prevailing gauche
interactions. The “gauche effect” is shown computationally not to be an accurate predictor of the lowest
energy conformer.