Half-sandwich complexes of group 9 metals with N,N′-ligands for CF3 -carbenoid alkylation of N-(pyrimidin-2-yl)indole

The complexes [CpM(N,N'-ligand)Br]PF6 (M = Rh, Ir; N,N'-ligand = 2,2'-bipyridyl, 1,10-phenanthroline) were synthesized by reactions of bromides [CpMBr2]n with 2,2'-bipyridyl or 1,10-phenanthroline followed by a counterion exchange. The replacement of cyclooctadiene in [CpIr(cod)I]I-3 with N,N'-ligands leads to complexes [CpIr(N,N'-ligand)I]I-3 (N,N'-ligand = 2,2'-bipyridyl, 1,10-phenanthroline). The structures of [CpRh(2,2'-bipyridyl)Br]PF6, [CpIr(2,2'-bipyridyl)I]I-3, and [CpIr(1,10-phenanthroline)Br]PF6 were determined by X-ray diffraction. The compounds prepared as well as the related the tris(pyrazolyl)borate derivatives [CpCoTp]PF6 and [Cp*MTp]PF6 (M = Rh, Ir) efficiently catalyze the alkylation of N-(pyrimidin-2-yl)indole with methyl 3,3,3-trifluoro-2-diazopropionate to selectively introduce the CF3 and carboxylate functions at the C3 position of the indole moiety. In contrast, the tris(pyrazolyl)borate cobalt complex [Cp*CoTp]PF6 predominantly provides the alkylation at the C2 position. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Novel Rh and Ir complexes were synthesized and their structures were determined by X-ray diffraction. The compounds prepared, as well as related derivatives, efficiently catalyze the alkylation of N-(pyrimidin-2-yl)indole with methyl 3,3,3-trifluoro-2-diazopropionate.