Friedländer Quinoline Synthesis Catalyzed by M(HSO4)n (M=Al, Mg, Ca) under Solvent-Free Conditions
Heterocycles Vol. 75, No. 10, 2513–2513
چکیده
Polysubstituted quinolines were synthesized from the 2aminobenzophenone, ethylacetoacetate or ketones in the presence of metal hydrogen sulfates [M(HSO 4 ) n ] in good to high yields at 70 ˚C under solvent-free conditions.2][3] Along this line, using metal hydrogen sulfates especially; Al(HSO 4 ) 3 , 4,5 Mg(HSO 4 ) 2 , 6,7 Ca(HSO 4 ) 2 , 8,9 which are low in toxicity, highly stable towards humidity, recyclable and air stable have found more attention.The importance of these solid acid catalysts is growing because of their safe and eco-friendly nature as attention is directed toward the development of clean and green technologies for important organic molecules to promote environmental safety.Quinolines and their derivatives are very important compounds because of their wide occurrence in natural products 10 and biologically active compounds. 11,12A large variety of quinolines have displayed interesting physiological activities and found attractive applications as pharmaceuticals and agrochemicals, as well as being general synthetic building blocks. 102][23] Amongst various methodologies reported for the preparation of quinolines, Friedländer annulation's is one of the simplest and most straightforward protocols.Friedländer synthesis involves a condensation followed by a cyclodehydration between an aromatic 2-aminoaldehyde or ketone and an aldehyde or ketone with a αmethylene functionality.Friedländer reaction can occur under base, 24 Brønsted acids, 25 Lewis acid, [26][27][28][29] inorganic salt, 30 iodine, 31 solid acid, 32 palladium, 33 nickel chloride, 34 potassium dodecatangestocobaltate