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Pd‐Catalyzed Reductive Carbonylation‐Ring Closure of Aryl Halides: A Direct Approach for Synthesis of Benzimidazoles
Author(s) -
EtemadiDavan Elham,
Iranpoor Nasser,
Khalili Dariush
Publication year - 2016
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201600732
Subject(s) - aryl , chemistry , halide , benzimidazole , catalysis , nitroaniline , medicinal chemistry , carbonylation , aryl halide , ligand (biochemistry) , dehydrogenation , combinatorial chemistry , ring (chemistry) , organic chemistry , carbon monoxide , palladium , biochemistry , alkyl , receptor
A novel protocol is reported for the facile one‐pot benzimidazole derivatives formation from Pd‐catalyzed reaction of aryl halides (X=I, Br, ‐Cl), Fe(CO) 5 , and o ‐diaminobenzene or o ‐nitroaniline. Aryl halides are first converted to aryl aldehydes using Fe(CO) 5 which then undergo ring closure with o ‐diaminobenzene or o ‐nitroaniline in DMF at 110 °C under Ar. In the case of o ‐nitroaniline, the reduction of the nitro group takes place before the cyclization step in the presence of reducing agents such as Fe(CO) 5 , released CO, Pd(0) and also P(III) in the reaction mixture. There is no need for employing P(III) ligand in case of aryl iodides while P(III) ligand is necessary for aryl bromides and chlorides to facilitate the reaction. In this reaction, Fe(CO) 5 is not only responsible as the CO source and reduction of ‐NO 2 functionality in o ‐nitroaniline, but also produces iron oxides residue in the reaction which are responsible for the dehydrogenation step.