The synthesis of esters under microwave irradiation using dry-media conditions

1993 ◽  
Vol 71 (1) ◽  
pp. 90-95 ◽  
Author(s):  
André Loupy ◽  
Alain Petit ◽  
Mohamed Ramdani ◽  
Celine Yvanaeff ◽  
Mustapha Majdoub ◽  
...  
Keyword(s):  
Microwave Irradiation ◽  
Organic Solvents ◽  
Phase Transfer Catalysis ◽  
High Pressures ◽  
Phase Transfer ◽  
Polar Molecules ◽  
Ionic Reactions ◽  
Microwave Effects

Practical and simple techniques are described for using nonmodified domestic microwave ovens as safe and convenient laboratory devices to obtain numerous esters. High pressures are avoided by conducting reactions with reactants impregnated on solid mineral supports in "dry media" or by phase transfer catalysis (PTC) in the absence of organic solvents. Two kinds of microwave effects are involved: (1) displacement of the equilibrium by evaporation of volatile polar molecules (water or alcohols) in esterifications and transesterifications; (2) acceleration of ionic reactions in carboxylate alkylations. As solvents are avoided, there is no need for sealed vessels and water separators.

scholarly journals Microwave-Assisted Improved Regioselective Synthesis of 12H-Benzopyrano[3,2-c][1]benzopyran-5-ones by Radical Cyclisation

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Pradipta Kumar Basu ◽  
Amrita Ghosh
Keyword(s):  
Microwave Irradiation ◽  
Phase Transfer Catalysis ◽  
Phase Transfer ◽  
Benzyl Bromide ◽  
Catalytic Amount ◽  
Ammonium Bromide ◽  
Catalysis Condition ◽  
Microwave Assisted ◽  
Tributyltin Hydride ◽  
Tetrabutyl Ammonium

Two new effective methodologies have been adopted for the preparation of 4-(2′-bromobenzyloxy)benzopyran-7-ones 3(a–h). In the first methodology, 4-hydroxy[1]benzopyran-2-ones 1(a–d) was alkylated with 2-bromobenzyl bromide 2a or 2-bromo-5-methoxy benzyl bromide 2b under phase transfer catalysis condition using lithium hydroxide/tetrabutyl ammonium bromide in N,N-dimethylformamide at 40–50°C and in the second method the microwave irradiation protocol has been exploited by simply mixing of 4-hydroxy[1]benzopyran-2-ones 1(a–d) with 25% excess of 2-bromobenzyl bromide 2a or 2-bromo-5-methoxy benzyl bromide 2b. A catalytic amount of TBAB and potassium carbonate were added and irradiated in an open Erlenmeyer flask in a microwave oven for 4–10 min. The tributyltin-hydride-mediated radical cyclisation of 3(a–h) was carried out under microwave irradiation to generate 12H-benzopyrano[3,2-c][1]benzopyran-5-ones 4(a–h) in 78–88% yield and in this technique yields were significantly improved and reaction time was shortened compared to the previously reported conventional radical cyclisation method.

ChemInform Abstract: Heterogeneous Phase Alkylation of Phenols Making Use of Phase Transfer Catalysis and Microwave Irradiation.

ChemInform ◽  
2010 ◽  
Vol 41 (17) ◽  
Author(s):  
Gyoergy Keglevich ◽  
Erika Balint ◽  
Eva Karsai ◽  
Judit Varga ◽  
Alajos Gruen ◽  
...  
Keyword(s):  
Microwave Irradiation ◽  
Phase Transfer Catalysis ◽  
Phase Transfer ◽  
Heterogeneous Phase
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