Palladium-Catalysed Amination of Hindered Aryl Halides with 9 H -Carbazole

Palladium-catalysed Buchwald-Hartwig amination of ortho-substituted hindered aryl bromides or chlorides with 9H-carbazole has been investigated. In the amination of 1-bromo- or chloronaphthalene with 9H-carbazole, the combined use of Pd2(dba)3 as a Pd precursor, Buchwald ligands with two tert-butyl groups and LiOtBu or lithium hexamethyldisilazide as a base led to satisfactory yields. N,N’-Bis[2,6-bis(diphenylmethyl)-4-methoxyphenyl]imidazol-2-ylidene (IPr*OMe), which is a bulky N-heterocyclic carbene ligand, showed similar activity as Buchwald ligands with two tert-butyl groups. In contrast, only IPr*OMe provided satisfactory yields in the amination of 2-bromo-1,1′-biphenyl with 9H-carbazole. The amination of 2-bromo- or chlorotoluene and 1-(2-bromo- or chlorophenyl)naphthalene with 9H-carbazole proceeded smoothly when the IPr*OMe ligand was used.