Intrigued by the small but measurable stereoselectivity observed in the formation of 4e, which cannot arise due to the proposed stereo-differentiating NH•••O H-bond, we examined the AT-CuAAC coupling between macrocycle 2 and aryl alkyne 3 and aryl azide 5 half-axles, neither of which contain a directing group, at rt in CH2Cl2 (Scheme 3a, entry 1), which gave geometric isomers (Em)-6 and (Zm)-6 in low but significant stereoselectivity (24% de), confirming that the AT-CuAAC reactions of 2 are not only biased by the Hbond identified in the case of rotaxanes 4. Analysis of the separated isomers of 6 by SCXRD allowed their absolute stereochemistry to be determined (Figure ).