Iodine a Simple, Effective and Inexpensive Catalyst for the Synthesis of Substituted Coumarins

Abstract

Molecular iodine is developed as an efficient catalyst in the von Pechmann condensation of phenols with b-ketoesters which leads to the formation of coumarin derivaties in excellent yields when carried out under microwave irradiation in a Prolabo Synthwave Microwave Reactor. The reaction also proceeds when carried out in the absence of solvent and at room temperature in acetonitrile.

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

“…It is widely applied for the synthesis of coumarins. 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.…”

Synthesis of a Series of 2-Indolylmethylene-Linked Compounds by Thermal Knoevenagel Condensation Under Catalyst- And Solvent-Free Conditions

“…Lewis acids [6][7][8][9] , zeolites 10 , surfactants 11 , different types of nanoparticles 12,13 have also been employed to catalyze the reactions. Moreover, the uses of ionic liquids 14 , microwave 15,16 and ultrasound 17 are found in the recent literature to effect this condensation under ecofriendly conditions.…”

“…Though a number of solvent-free methodologies are known for effecting Knoevenagel condensation 13,15,16,24 , only a few catalyst-free reaction conditions are reported 25,26 . Considering the importance of synthesis of new compounds containing an indole moiety and effecting Knoevenagel condensation under catalyst-and solvent-free conditions, we undertook the present work where 3-methylindole-2-carboxaldehyde (1) (readily available from a well-known indole compound skatole) 27 , with different active methylene compounds under the influence of heat only.…”

A facile synthesis of 2H-chromen-2-ones via Pechmann condensation under solvent free conditions using grinding technique

“…A large number of condensing agents such as strong acids H 2 SO 4 , HCl, H 3 PO 4 , F 3 CCOOH, solid super acid [ 9 , 14 -16 ] [ 14 -18 ] and ion exchange resins [ 19 ] have been used in the Pechmann condensation. Recently, the use of microwaves [ 20 ], ionic liquid as a Lewis acid [ 21 ], Zn/I 2 [ 22 ], Yb(OTf) 3 [ 23 ], LiBr [ 24 ], I 2 [ 25 ], CoPy 2 Cl 2 [ 26 ], p-TSA [ 27 ], BTSA/SiO 2 [ 28 ] and polyvinyl sulfonic acid [ 29 ] has also been reported. Some of the above mentioned reagents possess limitations, such as the use of harsh or hazardous chemicals, mainly organic solvents, expensive and large amount of reactants, a longer reaction time, elevated temperature and the formation of side products.…”