Scheme 1. Synthesis of Rotaxanes (R)/(S)-1-H⁺·2PF₆^–

Reagents and conditions: (i) (1) CF₃CO₂H, CH₂Cl₂, rt, 4 h; (2) 10, Et₃N, MeOH, rt, 24 h; (3) NaBH₄, THF/MeOH, rt, 18 h, 32% (from (R)-9) and 34% (from (S)-9); (ii) (1) HCl (1.0 M in Et₂O), CH₂Cl₂, rt, 8 h; (2) KPF₆, CH₂Cl₂/acetone/H₂O, rt, 16 h, 98% (for (R)-11-H⁺·PF₆^–) and 91% (for (S)-11-H⁺·PF₆^–); (iii) Cu(CH₃CN)₄PF₆, TBTA, CH₂Cl₂, rt, 3 d, 35% (for (R)-13-H⁺·PF₆^–) and 19% (for (S)-13-H⁺·PF₆^–); (iv) (1) CH₃I, rt, 4 d; (2) KPF₆, CH₂Cl₂/acetone/H₂O, rt, 5 h, 68% (for (R)-1-H⁺·2PF₆^–) and 55% (for (S)-1-H⁺·2PF₆^–); (v) (1) CH₃I, rt, 4 d; (2) KPF₆, CH₂Cl₂/acetone/H₂O, rt, 18 h, 58% (for (R)-2-H⁺·2PF₆^–) and 98% (for (S)-2-H⁺·2PF₆^–).