Assembly of Water-Soluble, Dynamic, Covalent Container Molecules and Their Application in the Room-Temperature Stabilization of Protoadamantene

The thermodynamically controlled reactions of water-soluble tetra-formylcavitand 2 with two equivalents of H-2(CH2)(n)NH2 (n=2-4) in the presence of a suitable templating guest give hemicarceplexes 1a-e.guest, the yield of which depends on the match between size and shape of the guest and that of the inner phase. These hemicarceplexes are dynamic and dissociate upon addition of acid and reform upon basification. In water, they exchange guests through temporary hydrolysis of imine bonds. To test 1b as molecular reaction flask, 3-noradamantyldiazirine 6 was encapsulated and photolyzed at 350 nm to produce Bredt olefin protoadamantene 5 and 1-noradamantyldiazomethane 8 in a 4:1 ratio. Encapsulated protoadamantene is stable for days at room temperature in (CD3)(2)SO/CD3CN (t(1/2)=5.5 days) and has a lifetime of several minutes in D2O.