Palladium(II)-Catalyzed Oxidative C–H/C–H Coupling and Eliminative S_N^H Reactions in Direct Functionalization of Imidazole Oxides with Indoles

Abstract

Two novel synthetic approaches to realize the direct C(sp(2))-H bond functionalization in cyclic nitrones are reported. Palladium(II)-catalyzed oxidative C-C coupling of 2,2-dialkyl-4-phenyl-2H-imidazole 1-oxides with indoles was shown to result in the formation of 5-indolyl-3-yl derivatives, while nucleophilic substitution of hydrogen (S(N)(H)) at C(5) of the same imidazole system was found to afford the corresponding deoxygenated compounds.

C(sp2)–H functionalization in non-aromatic azomethine-based heterocycles

“…Functionalization of azomethine derivatives involving an S N H (AE) pathway was not reported until the last decade. 24 Notably, this 'Addition-Elimination' strategy has been frequently applied for the modification of (hetero)aromatic substrates, but not for saturated systems. 22c In contrast, the alternative oxidative S N H (AO) protocols are well documented here, as illustrated by transformations of aldonitrones 15, 16ab (Scheme 5).…”

Influence of Aromatic Residues on the Material Characteristics of Aβ Amyloid Protofibrils at the Atomic Scale

“…Dual CH activation/arylation reactions have also been described, such as the elegant coupling reactions between indoles and imidazole N ‐oxides,111 pyridine N ‐oxides,112 azine N ‐oxides,113 or caffeine,114 (Scheme ).…”

Molybdenum‐Catalyzed Deoxygenation of Heteroaromatic N‐Oxides and Hydroxides using Pinacol as Reducing Agent

“…However, selective monoreduction to the corresponding 1-hidroxybenzimidazole with one equivalent of pinacol could not be achieved. In the same way, 2H-imidazole 1-oxides such as 9, [24] as well as triazole N-oxides such as 11, [25] were also efficiently deoxygenated to 2H-imidazole 10 [26] and 2H-1,2,3-triazole 12, respectively. Finally, also N,N-dimethylaniline N-oxide 13 [27] could be deoxygenated to the corresponding aniline 14, showing that this methodology is also suitable for non heteroaromatic N-oxides.…”