Chiral 2 + 3 Keto-Enamine Pseudocyclophanes Derived from 1,3,5-Triformylphloroglucinol.

The reactions of 1,3,5-triformylphloroglucinol with (1R,2R)-1,2-diaminocyclohexane, (1R,2R)-1,2-diphenylethylenediamine, or (R)-2,2'-diamino-1,1'-binaphthyl result in the formation of enantiopure [2 + 3] keto-enamine condensation products, in contrast to analogous reactions of 1,3,5-triformylbenzene, where [4 + 6] Schiff base cages are formed. The X-ray crystal structure of the diaminocyclohexane 2 + 3 derivative as well as modeled structures of other compounds of this type show cyclophane-like molecules with close contact between the phloroglucinol rings. Density Functional Theory (DFT) calculations confirm that there is a sizable π-π interaction between these rings influencing the conformation of these molecules.