Convenient and efficient protocols for coumarin synthesis via Pechmann condensation in neutral ionic liquids

A convenient synthesis of coumarins using reusable ionic liquid as catalyst

“…Non-chloroaluminate acidic ionic liquids, which are air and moisture stable, have been developed and applied for acidic reactions. One recent report showed the use of neutral ionic liquid in the presence of POCl 3 as catalyst, which is highly toxic and difficult to use (15). The application of Brønsted acidic task-specific ionic liquids (TSILs) as catalytic materials is growing continuously in the catalytic *Corresponding author.…”

Imidazolium Ionic Liquids: An Environment-Friendly Medium for Various Applications

“…A large number of reagents were used for this reaction, including sulfuric acid, phosphorus pentoxide, aluminum chloride, trifluoroacetic acid, SnCl 2 [97], oxalic acid [98], alum (KAl(SO 4 ) 2 ·H 2 O, silica triflate, iodine, [99] etc., which are preferred for the reaction. Recently, a number of studies have also shown that ILs, either neutral [100] or acidic [101][102][103], promoted coumarin synthesis via the Pechmann condensation. Sing et al [104] [bmim]Br IL was used in the one-pot four-component methodology for the synthesis of 1,2,4,5-substituted imidazoles from benzil, aldehydes, amines, and ammonium acetate under conventional heating and MW irradiation by Hasaninejad et al [107] (Scheme 7.6).…”

Ionic Liquids Recycling for Reuse

“…The above ILs have been reused for consecutive four cycles without loss in their efficiency . Potdar et al (2005) found the yields of the above reactions obtained by employing chloroaluminate ILs or neutral ILs with catalytic amount of acid at room temperature compare well to those obtained at high temperature. They also found that the IL [bmim]PF 6 can be recycled efficiently and used consecutively for three runs without any considerable loss in its activity (see Table 5).…”

“…Furthermore the products obtained were of the same purity as in the first run. Potdar et al (2005) also presented a general work up procedure for recycling of ILs: The reaction mixture was quenched with 10% aqueous NaOH solution and settled. The settled down IL was extracted with dichloromethane.…”