Scheme 2. Synthesis of Ether-Based Ligand 7 and Macrocycles 8a and 8ba.
a (i) 1-bromo-2-chloroethane, K2CO3, Acetone, Reflux; (ii) 1,3-propanedithiol, Y(OTf)3 (5 mol %), CH3CN; (iii) KPPh2, THF; (iv) S8, THF;(v) NaNO2, AcCl/H2O, CH2Cl2, 0 °C → rt; (vi) 5-mesityldipyrromethane, BF3•OEt2, DDQ, NEt3, CHCl3, 4 Å Molecular Sieves; (vii) Zn(OAc)2•2H2O, 4:1 CHCl3/MeOH, Reflux; (viii) Cp2ZrHCl, THF, 60 °C; (ix) [Rh(CO)2(Cl)]2, CH2Cl2/THF; (x) [Cu(CH3CN)4]PF6, CH2Cl2/THF.