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Reagents and conditions: (a) Boc-piperazine, Pd(OAc)2, cataCXium A, NaOtBu, toluene, 120 °C, 44%; (b) LiHMDS, Pd2(dba)3, DavePhos,43 dioxane, 100 °C, 73%; (c) TFA, CH2Cl2, 97%; (d) Br-(CH2)n-CO2R, K2CO3, DMF; (e) R = tBu:TFA/CH2Cl2, 13a: 89% over two steps; 13b: 30% over two steps; (f) R = Me:LiOH, MeOH/THF/H2O; 13c: 8% over two steps.
