Tröger's Base-Embedded Pillararenes─Macrocycles with Both Fixed and Conformational Chirality.

Tröger's base-embedded pillararenes ( P[1]TB[3]A ), which combine Tröger's base ( TB ) with dialkoxybenzene units, were prepared via a fragment-coupling macrocyclization strategy. The TB unit in macrocycle P[1]TB[3]A provides a fixed chiral source, while 1,4-alkoxybenzene segments flip quickly to change their arrangement, which could provide reversible conformational chirality for those macrocycles. This rare example of macrocycles holding both fixed and conformational chirality lays a good foundation for expanding pillararenes using the fixed chiral source.