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 similar to 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.

Automated summary

A series of alkyl-O-methyl aldoximes with various functional groups were synthesized and showed E-Z isomerization in organic solutions. However, these compounds exhibited high selectivity for the cis-Z isomer when confined in a water-soluble capsule. The affinities for the chalcogen-bonded capsule depended on the guest chain length and functional groups. An E-to-Z isomer selectivity of >99% was achieved with a chain length of 14 heavy atoms, and the isomerization was accelerated by sonication.