Replacing the solvent with THF marginally improved the selectivity (28% de, entry 2), as did lowering the reaction temperature to -20 °C (40% de, entry 3) but, as with 4d, reduced selectivity was observed at lower temperatures (entries 4 and 5). Using EtOH as a reaction solvent was comparable to THF (entry 6). Interestingly, when a propargylic alkyne was employed with 5 in THF to generate rotaxane 7, no stereoselectivity was observed (Scheme 3b), whereas the reaction of an alkyl azide and 3 to give rotaxane 8 proceeded in low stereoselectivity (14% de). This suggests that steric hindrance associated with the coupling partners plays a role in determining facial selectivity in the AT-CuAAC reactions of 2, as has previously been observed in the synthesis of mechanical planar chiral rotaxanes, 25 although the precise origin of the stereocontrol observed in these simple systems remains unclear.