Scheme 1. Synthetic Strategy for the Preparation of Target Compounds 4a–f and 5a,b.

Reagents and conditions: (i) iodobenzene, Pd₂(dba)₃, SPhos, t-BuOK, toluene, 100 °C, on; (ii) alkyl bromide, K₂CO₃, ACN, 50 °C, on; (iii) acyl chloride, triethylamine (TEA), CH₂Cl₂, rt, 2 h; (iv) TFA, CH₂Cl₂, rt, 4 h; (iv) Boc₂O, CH₂Cl₂, rt, on.