Transition-Metal-Catalyzed Arylation of Nitroimidazoles and Further Transformations of Manipulable Nitro Group

Abstract

Pd- or Ni-catalyzed C-H arylation of 4-nitroimidazole derivatives directed by a manipulable nitro group was developed. The reaction tolerates a wide range of substituted aryl halides and 4-nitroimidazoles. The experiments indicated that the nitro group has influence on regioselectivity of the reaction. In addition, we have shown that the efficiency of the Suzuki-Miyaura cross-coupling reaction of nitroimidazoles is slightly lower in comparison to the direct C-H arylation. The exploration of the chemical potential of the nitro group and a putative reaction mechanism are discussed.

Pd(0)-Catalyzed Direct Inter- and Intramolecular C–H Functionalization of 4-Carboxyimidazoles

“…In particular, the first selective direct C2-H (het)arylation and alkenylation of N-benzyl imidazole-4-carboxylates with bromo-and iodo(het)arenes and bromoalkenes under Pd(0)/Cu(I)-cooperative catalysis has been described giving an efficient access to a broad library of C-2-functionalized methyl imidazole-4-carboxylate compounds. In contrast to previous observations in N-substituted 4-nitroimidazole-4-carboxylates, 29 in our case the intermolecular CMD-based reactivity does not operate at C5 when both C4 and the imidazole nitrogen are substituted. Conversely, using N-(o-halogenobenzyl) imidazole-4-carboxylates as starting materials, arylation occurred under K 2 CO 3 -assisted CMD-based conditions to produce novel C-5-arylated fused imidazoles with five-to seven-membered central rings as major products.…”

Copper-catalyzed direct C–H arylselenation of 4-nitro-pyrazoles and other heterocycles with selenium powder and aryl iodides. Access to unsymmetrical heteroaryl selenides

“…), [80][81][82][83]85,[88][89][90] halogen substituents (mostly uorine or chlorine), [80][81][82][83]85,[88][89][90][91][92][93] and ring heteroatoms (namelysulfur, nitrogen, and oxygen). The use of the nitro group as a regiodirecting substituent in C-H activations has been investigated previously 94,95 also by our group in the context of arylation of nitro-pyrazoles, 96 nitro-imidazoles 97 and other nitro-heteroarenes. 98 Herein we describe a one-pot method to obtain unsymmetrical diorganyl selenides from C-H activated heterocycles (including nitro-substituted), aryl iodides and elemental selenium powder.…”

Synthesis and in vitro evaluation of new 5-substituted 6-nitroimidazooxazoles as antikinetoplastid agents

“…The initial conditions ( Table 1, entry 1) were inspired from a previously reported protocol for CH-activation reaction in 4nitroimidazole series involving Pd(PPh 3 ) 2 Cl 2 , CuI and pivalic acid as catalyst, K 2 CO 3 as base, in DMA as solvent at 130 C [22]. Only traces of the desired product 3 were obtained, and unidentified degradation products were observed from LC-MS monitoring.…”