Intermediates in the reaction ofo-phenylenediamine with carbonyl compounds and their subsequent conversions

Abstract

INTERMEDIATES IN THE REACTION OF o-PHENYLENE-DIAMINE WITH CARBONYL COMPOUNDS AND THEIR SUBSEQUENT CONVERSIONS K. N. Zelenin, I. V. Ukraintsev, and V. V. AlekseevThe reaction of o-phenylenediamine with aldehydes and ketones has been studied using PMR spectroscopy. It has been established that the reaction begins with the formation of monoimines (isolated in condensations with aromatic aldehydes) which are cyclized to the corresponding benzimidazolines. The latter are converted in the reactions involving aldehydes and pinacolone into 2-substituted benzimidazoles, but with acetone and acetophenone give 2, 3-dihy dro-l H-benzo[b]-l , 4-diazepine derivatives.

Acetic acid-promoted condensation of o-phenylenediamine with aldehydes into 2-aryl-1-(arylmethyl)-1H-benzimidazoles under microwave irradiation

“…This can be indicative that the reaction probably occurs via path a, with the formation of A, followed by 1,3-hydride transfer, according to previous suggestions. 32,36,41,47 However, the formation of 2-(2-furyl)benzimidazole 3j in minor yield in the case of furylaldehyde (Table I) can be explained possibly through path b involving the formation of dihydrobenzimidazole C intermediate followed by dehydrative oxidation in air to yield 2-arylbenzimidazole 3, as suggested by Xiangming 48 and Zelenin et al 49 A direct oxidative condensation of aldoses with diamines using molecular iodine in AcOH has already been reported for an improved synthesis of aldo-benzimidazoles and aldo-naphthimidazoles, which supports the observations in this work. 50 It is important to emphasize that, when these reactions were conducted under nitrogen atmosphere, no formation of compound 3 was detected and compounds 2a-m were isolated as the sole products in slightly improved yields.…”

Grindstone chemistry: protic ionic liquid-substrate tuned green synthesis of 1,2-disubstituted and 2-substituted benzimidazoles with outstanding selectivity

“…substituted benzimidazole and the absence of oxygen leads to 1,2-disubstituted benzimidazole using excess aldehydes. 23 Subsequent release of PIL-II$H leads to synthesis of 2-substituted benzimidazoles (4). In our experiments PIL-II is expected to activate aldehyde rst and rapidly perform condensation with one of the -NH 2 groups of OPD to form A, which on ring closing followed by a hydride shi furnished 3 as the sole product (eqn (1), Scheme 3).…”

“…Under the reaction conditions bis-imine (A, eqn ( 1)) formation with aromatic aldehydes possessing an electron withdrawing group might be disrupted by the powerful PIL-II catalyst and the second amino group of monoimine (B, eqn ( 2)) is allowed for ring closing to construct the dihydrobenzimidazole-PIL-II intermediate (D). 23 Subsequent release of PIL-II$H leads to synthesis of 2-substituted benzimidazoles (4). We performed another experiment using 2-chlorobenzaldehyde and OPD in the presence of 5 mol% of PIL-II under a N 2 atmosphere, we were pleased to observe that only 2-(2-chlorophenyl) benzimidazole (4a) was formed aer 1 h at room temperature in 72% yield (Table 2, entry 1).…”

A Fluorimetric Method Based on an Imidazole Compound for Cu2+ Determination in Tap Water

“…However, sometimes the reaction proceeds to a further step, and the cyclization of the formed diimine compound results in benzimidazole compounds. Many benzimidazole derivative compounds synthesized in this manner have been reported in the literature [1][2][3][4][5][6][7][8]. Sometimes a catalyst is used in the synthesis of benzimidazole compounds [1,[4][5][6].…”

“…Many benzimidazole derivative compounds synthesized in this manner have been reported in the literature [1][2][3][4][5][6][7][8]. Sometimes a catalyst is used in the synthesis of benzimidazole compounds [1,[4][5][6]. Acidification was effective in the formation of the cyclization [2,3].…”