Green Chemistry Metrics

One‐pot Synthesis of Benzo[4,5]imidazo[1,2‐a]pyridine Derivatives in Aqueous Conditions

“…It should be noted that this product was obtained earlier in isopropanol in the presence of piperidine under microwave irradiation at 100°C during 5 min with a yield of 78% (the conditions from way A, Scheme 1). Thus, further, we aimed to apply the found aqueous conditions for the synthesis of different benzo [4,5]imidazo[1,2-a]pyridine derivatives 10 from available 1,3-cyclohexandiones (1b-е).…”

“…Application of 2-cyanobenzimidazole in consecutive one-pot interaction with cyclic 1,3-diketones and DMFDMA under various conditions proceeds selectively leading to formation of 4-oxo-1,2,3,4-tetrahydrobenzo [4,5] imidazo[1,2-a]quinolin-6-yl cyanides (10). Water was found to be the optimal medium for the majority of the cases allowing facial synthesis and isolation of the pure products.…”

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in Wiley Online Library (wileyonlinelibrary.com).One-pot reaction of cyclic 1,3-diketones, dimethylformamide dimethylacetal (DMFDMA) and 2-(1H-benzo[d] imidaz-2-yl)acetonitrile was found to be a highly selective process leading to 4-oxo-1,2,3,4-tetrahydrobenzo [4,5] imidazo[1,2-a]quinolin-6-yl cyanides. Optimized reaction conditions using water as solvent at room temperature or under microwave heating allowed high yields of the target products required no additional purification.

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Organic Synthesis without Conventional Solvents

“…[7,86] Applying a microreactor, the exothermic Paal-Knorr pyrrole synthesis could be performed without a solvent. The reactants are simply mixed in a vessel and heated (e.g.…”

“…[7] To clarify, in this overview, we do not focus only on approaches that are entirely solvent-free, but also include new, "unconventional" reaction media. Whereas mechanochemical reactions, occurring in the solid state, are generally accepted as solvent-free, this is not the case for reactions containing a liquid reactant since this may also act as solvent, especially when it is present in large excess with respect to another solid component.…”