Selective Binding and Isomerization of Oximes in a Self-Assembled Capsule.

A series of straight-chain (C7-C13) alkyl-O-methyl aldoximes (R-C(H)═NOMe) were synthesized with various functional groups at the remote ends (alkenes, halogen, -COOH, and NH2). Their isomers about the C═N bond showed ∼60-40% E-Z-ratio in organic solutions. Surprisingly, their confinement in a water-soluble capsule with benzoselenodiazole walls shows high selectivity for the cis-/Z-isomer. Their relative affinities for the chalcogen-bonded capsule at room temperature depend mainly on the guest chain length and functional groups. A chain length of 14 heavy atoms showed especially high E- to Z-isomer selectivity (>99%) and was used in separation. The E-Z isomerization occurred only in the capsular cavity at room temperature and was accelerated 10-fold by sonication. The Z-isomer selective binding, separation, and E-Z isomerization are supported by NMR, DOSY, and computational studies.

Recent Advances in the Applications of Water-soluble Resorcinarene-based Deep Cavitands.

We review here the use of container molecules known as cavitands for performing organic reactions in water. Central to these endeavors are binding forces found in water, and among the strongest of these is the hydrophobic effect. We describe how the hydrophobic effect can be used to drive organic molecule guests into the confined space of cavitand hosts. Other forces participating in guest binding include cation-π interactions, chalcogen bonding and even hydrogen bonding to water involved in the host structure. The reactions of guests take advantage of their contortions in the limited space of the cavitands which enhance macrocyclic and site-selective processes. The cavitands are applied to the removal of organic pollutants from water and to the separation of isomeric guests. Progress is described on maneuvering the containers from stoichiometric participation to roles as catalysts.