Heterotopic Host Molecules for Binding Two Different Guests

Abstract

Host molecules with boron-containing acceptor and crown ether donor positions like compound 1, depicted for the preceding communication, can selectively bind alcohols and amines. The Lewis acidic boron center engages with the Brønsted properties of the alcohol/amine system so that the alkoxy ion is bound to boron and the ammonium ion to the crown ether unit. This is shown schematically in the equation below. The structure of the host/guest1/guest2 is highly unusual.