The process by which 2a racemizes was simulated using DFT calculations (Figure ). isomerizes to achiral conformer C via a small activation barrier (1.9 kcal mol -1 ). Further isomerization finally affords an inverted figure-eight conformation. The overall activation barrier for this process (33.7 kcal mol -1 ) agrees closely with the experimentally determined value. It is worth noting that we also found another possible isomerization route (Figure ).