High Surface Area MgO as a Highly Effective Heterogeneous Base Catalyst for Three-Component Synthesis of Tetrahydrobenzopyran and 3,4-Dihydropyrano[c]chromene Derivatives in Aqueous Media

Abstract

Magnesium oxide (MgO) as a highly effective heterogeneous base catalyst effectively catalyzes the three component reaction of aryl aldehydes, malononitrile and a-hydroxy or a-amino activated C-H acids such as 1,3-cyclohexanedione, dimedone, 4-hydroxy-6-methylpyrone, 4-hydroxycoumarin, 1,3-dimethylbarbituric acid and 1,3-dimethyl-6-amino uracil to the formation of the corresponding pyran annulated heterocyclic systems. The catalyst is inexpensive and easily obtained, stable and storable, easily recycled and reused for several cycles with consistent activity.

Microwave-Assisted Synthesis of Novel 2H-Chromene Derivatives Bearing Phenylthiazolidinones and Their Biological Activity Assessment

“…Method 3-phenylisothiazolidin-4-one (13) with benzaldehyde (12) and thiourea (18) proceeded smoothly in DMF containing 3-4 drops of glacial AcOH acid via microwave assisted as well as conventional synthesis to give 5-(2-(6-hydroxy-2-oxo-2H-chromen-4-yl)-7-phenyl-5-thioxo-5,6,7,7a-tetrahydrothiazolo [4,5- (20), respectively, (Schemes 7 and 8, Table 1). In the IR spectrum of the latter product absorption bands were observed at 1378, 1684 and 3250-3486 cm −1 corresponding to (C=Sstr), (C=Ostr) and (N-Hstr) vibrations, respectively.…”

“…Moreover, they can also be employed as cosmetics and pigments [13] and utilized as potential biodegradable agrochemicals [15]. Some of these compounds have been already prepared in the presence of piperidine [16], diammonium hydrogen phosphate (DAHP), S-proline [17], K2CO3 under microwave irradiation [18], H6P2W18O62· 18H2O [19], MgO [20] and tetrabutylammonium bromide (TBAB) [21]. Each method has its own advantages and disadvantages.…”

Synthesis of Fe 3 O 4 /Eggshell Nanocomposite and Application for Preparation of Tetrahydrobenzo[b]Pyran Derivatives

“…Several methods for the synthesis of tetrahydrobenzo [b]pyran derivatives have been reported for instance 4H-benzo [b]pyrans were synthesized from α-cyanocinnamonitrile derivatives in a single step reaction which is catalyzed by acid or base [10][11][12]. Several methods stated for the synthesis of these compounds in the presence of catalysts such as sodium bromide [13], hexadecyldimethylbenzylammonium bromide [14], tetramethylammonium hydroxide [15], diammonium hydrogen phosphate [16], fluoride ions [17], magnesium oxide [18], sodium selenite [19], iodine [20], H6P2W12O62·H2O [21], tetrabutylammonium bromide [22], cerium(III) chloride [23].However, each of the above-mentioned method has a drawback such as: long reaction time, severe reaction conditions, use of toxic reagents and low reaction yield. Thus, the development of fast, suitable, and environmentally friendly methods for the synthesis of tetrahydrobenzo [b]pyrans remains essential strategy to overcome stated problems.…”

Two ligand oxidio-vanadium(IV) complexes as novel efficient catalysts in multicomponent reactions for synthesis of tetrahydrobenzopyran derivatives

“…Various catalytic systems such as potassium phthalimide-N-oxyl (POPINO) [19], CaCl 2 under ultrasonic irradiation [20], high surface area MgO [21], tetrabutylammonium bromide [22], Nano-ZnO [23], K 3 PO 4 [24], NaOCl under grinding [25], SiO 2 nanoparticles [26], triethylbenzylammonium chloride (TEBA) [27] and Ni(NO 3 ) 2 .6H 2 O [28] have been reported. Each of these methods has its own merits, but the use of toxic organic solvents, expensive catalysts, containing transition metals, difficult work up, high reaction time, and low yields are drawbacks of these procedures.…”