Enantiomerically Pure Tribenzotriquinacenes through Stereoselective Synthesis

The dynamic multicomponent syntheses of nanometer-sized chiral molecular cubes 1a and 1b from 8 tritopic 90 degree corner units and 12 linear spacers using an edge-directed approach is described. Thus, the TFA-catalyzed reaction of 8 equiv C3-trihexadecyloxy-triformylcyclotribenzylene 2 as corner unit with 12 equiv of 1,4-phenylenediamine 3a or benzidine 3b as spacers yields nanocubes 1a and 1b, respectively in close to quantitative yield. The same reactions carried out with enantiomerically pure (P)-2 (>99% ee) gave the homochiral cubes (all-P)-1a and (all-P)-1b. Force field calculations predict an edge length of 17 A and 21 A for 1a and 1b, which is consistent with their dimensions estimated from DOSY experiments. Furthermore, the asymmetric synthesis of (P)-2 through a dynamic thermodynamic resolution is described. This approach is based on the TFA-catalyzed reaction of racemic 2 with (R,R)-1,2-diaminocyclohexane (R)-5, which leads to a chiral cryptophane (>90% yield) that is built-up from two (P)-2 linked together with three diamines (R)-5. Hydrolysis of this cryptophane provides (P)-2 with >99% ee.