Introduction of aromatic and heteroaromatic groups in the 2-and 8-positions of the Troger's base core by Suzuki, Stille and Negishi cross-coupling reactions -: A comparative study

A comparative study on the bis(functionalization) of the Troger's base core by aromatic and heteroaromatic groups using palladium-catalyzed cross-coupling reactions is presented. Three different reactions, the Suzuki, Stille, and Negishi couplings, were investigated using Troger's base analogues equally substituted in the 2,8-positions with (HO)(2)B, Bu3Sn and ZnCl groups, respectively, as the metallated comportent. Six aryl halides with different electronic and steric properties were employed as coupling partners. The presence of the bulky and electron-rich phosphane P(tBu)(3) as cocatalyst was found to play an important role. In addition, the palladium source, [Pd(PPh3)(4)] or [Pd-2(dba)(3)], was also found to be all important factor for the yield of the reactions, The Suzuki coupling was found to be the best method in general, giving excellent yields for most aryl halides, whereas the Stille and Negishi couplings gave moderate to good yields. Finally, the crystal structures of the 4-nitrophenyl- and the 2-pyridyl-appended analogues of Troger's base, 7d and 7f, are presented in the Supporting Information.