Solid Phase Synthesis of Benzimidazole Ketones and Benzimidazole Chalcones under Solvent-Free Conditions (original) (raw)
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Chinese Chemical Letters, 2008
Glyoxylic acid (5 mol%) performs as a novel highly water-soluble catalyst for the synthesis of 2-aryl-1-arylmethyl-1Hbenzimidazoles from a wide range of substituted o-phenylenediamines and various substituted aldehydes in good to excellent isolated yields (85-95%) using water as solvent at ambient temperature. The remarkable advantages offered by this method are easily and inexpensive available catalyst, simple procedure, mild conditions, much faster (20-40 min) reactions and excellent yields of products.
The Journal of Organic Chemistry, 2017
Journal of Organic Chemistry nitro products 3q (61%), and 3t (60%) were tolerated under the optimized conditions. It is noteworthy that aryl methyl ketones bearing electron-donating groups were found to give better results than those with electron-withdrawing groups (Table 2). To our delight, some of the fused acetophenones (α/β-acetyl naphthalenes) and heteroaromatic ketone (2-acetylthiophene) also resulted the corresponding products 3ae-3ah with 65-78% yield. Unprotected functional groups like amine (3ai), hydroxyl(3aj), nitrile (3ak), ester (3al), acid (3am) containing acetophenones were also tolerated under standard condition to give desired products in low to moderate yields (25-50%). Expanding the scope of the reaction, different o-phenylenediamines were employed in this reaction. Methyl substituted benzene-1,2-diamine reacts with both electron-rich and poor aryl/heteroaryl methyl ketones afforded the products in good yields (Table 2, 3b, 3l, 3o, 3x, 3z & 3ah, 58-68%). Furthermore o-phenylenediamine bearing electron-withdrawing groups like 4flouro & 4-chloro o-phenylenediamine produced products 3f (55%) and 3e (58%) in good yields. Additionally 4, 5 dichloro-substituted o-phenylenediamine furnished the product 3ac in 52% yield. Surprisingly, benzoyl substituted o-phenylenediamine gave very low yield with electronrich acetophenones 3c (44%), 3g (35%), 3j (40%), 3m (35%), 3w (32%), and no product formed with electron deficient substrates. Interestingly, diaminomaleonitrile offered corresponding imidazole 3ad in 50% yield.
Synthesis of 1-Alkyl/Aralkyl-2-(1-arylsulfonylalkyl)benzimidazoles under PTC Conditions
ChemInform, 2007
2-(α-chloroalkyl)benzimidazoles 1 on reaction with arylsulphinate sodium salt 2, in CH 3 CN under PTC conditions, gives 3 which on alkylation yields 1-alky/aralkyl-2-(α-aryl sulfonylalkyl)benzimidazoles 4. Alternatively, 4 can also be prepared by the reaction of 2 with 1-alkyl/aralkyl-2-(α-chloroalkyl)benzimidazole 5 in CH 3 CN using triethylbenzylammonium chloride (TEBAC) as PTC. 5 are obtained from 1 in turn, by alkylation in CH 3 CN under PTC conditions.
Synthesis of new 1-(2-benzimidazolyl)-2-propen-1-ones
Indian Journal of Heterocyclic Chemistry, 2004
Twenty analogs of chalcones have been prepared fiom the Claisen-type condensation of 2-acetylbenzimidazolewith variously substltuted aromaticaldehydes inthe presence of catalytic amounts of piperidine. Chalcones and their heterocylic analogs are useful intermediates in organic systemsl. Moreover, these compounds are known to display a large number of different biological activities2. In continuation of previous research concerning the synthesiss and reactivi$4,s of
Chinese Chemical Letters, 2008
A simple one-pot synthetic method for the preparation of 2,4,5-triaryl-1H-imidazoles from benzoin or benzil, ammonium acetate, aromatic aldehydes, and ZrOCl 2 Á8H 2 O catalyst is described. The ZrOCl 2 Á8H 2 O catalyst was found to be equally effective for aromatic and heteroaromatic aldehydes and also for the preparation of substituted 1,4-di(4,5-diphenylimidazol-yl) benzene.
Benzimidazoles were synthesized by the copper-catalyzed, one-pot, three-component reaction of 2haloanilines, aldehydes, and NaN 3 . The reaction was optimized when 2-iodo-or 2-bromoanilines (1.0 equiv), aldehydes (1.2 equiv), NaN 3 (2.0 equiv), 5 mol% of CuCl, and 5 mol % of TMEDA were reacted in DMSO at 120°C for 12 h. Good yields resulted, and the reaction showed tolerance toward functional groups such as ester, nitro, and chloro. Aliphatic and heteroaromatic aldehydes also afforded the desired products in moderate to good yields.