Ridaphun Nongrum

Nickel nanoparticles assisted regioselective synthesis of pyrazoloquinolinone and triazoloquinazolinone derivatives

Biologically important pyrazoloquinolinone and triazoloquinazolinone derivatives were synthesized by the condensation reaction of 3-amino-1H-1,2,4-triazole/3-amino-5-methyl-1H-pyrazole, dimedone and aryl aldehydes using catalytic amount of magnetically retrievable nickel nanoparticles under reflux condition. This protocol eliminates the usage of toxic reagents, complex work-up conditions, etc., with the added benefit of reusability of the catalyst without compromising the yield or purity of the product.

A nano-organo catalyzed route towards the efficient synthesis of benzo[b]pyran derivatives under ultrasonic irradiation

An efficient, one-pot synthesis of benzo[b]pyrans catalyzed by vitamin B1 functionalized Fe2O3@SiO2 NPs under ultrasonic conditions is reported herein. The nano-organocatalyst was synthesized and characterized by FT-IR, TEM, EDS, powder XRD, etc. Several benzo[b]pyran derivatives were prepared with satisfactory yields and the nanocatalyst was magnetically retrieved and recycled. The salient features of this protocol include convenient work-up procedure, mild reaction conditions, easy catalyst recovery, shorter reaction time and use of green solvents. Ultrasound energy has been meticulously exploited for the synthesis of a nano-organocatalyst as well as for the preparation of several benzo[b]pyran derivatives. The biological activity of the synthesized benzo[b]pyrans were investigated and one of the derivatives was found to demonstrate profound activity in suppressing the side-effects of chlorpyrifos, an insecticide on the morphology of the external gills of the Duttaphrynus melanostictus tadpoles.

Synthesis of substituted hexa-3,5-dienoic acid methyl esters from conjugated dienones

Substituted hexa-3,5-dienoic acid methyl esters (2) were conveniently prepared in one step by 1,2-carbonyl transposition of the corresponding dienones (1) using lead(IV) acetate and boron trifluoride–diethyl ether in benzene at room temperature.

A NOVEL ONE-POT SYNTHESIS OF SUBSTITUTED PYRIDAZINES: A GENERAL METHOD OF PREPARATION OF 3,4,6-TRI ARYL PYRIDAZINES

3,4,6-triaryl pyridazines 4 were conveniently prepared in one step by the condensation of aryl methyl ketones and 1,2-diketones in presence of base, followed by cyclisation with hydrazines. Introduction: Owing to their wide application as drugs (1,2) and agrochemicals (3) pyridazines have aroused great interest in recent years. The introduction of aryl groups into the ring system allows modulation of their biological activity (4). While 3,6-diaryl pyridazines can be easily obtained using various methods (5a-f) our literature survey showed that there are only a few reports on the synthesis of triaryl pyridazines. Some of the reported syntheses include the following: (i) Cyclisation of dibenzoyl styrene with hydrazine; (6) (ii) Reaction of 3,6-diaryl-sym-tetrazines with phenyl acetylene (7) and phenyl acetaldehyde; (8) (iii) Oxidation of the condensed product of desylacetophenone with hydrazine (9) and (iv) Cyclisation of acetophenone deoxybenzoin azine and subsequent aromatisation. (10) However these methods are limited to triphenyl pyridazines and hence suffered from lack of generality. In 1900, Francis Robert Japp and James Wood (6) first described the preparation of 3, 4, 6-triphenyl 1, 2-diazine by a multi step procedure where each intermediate was isolated and purified. Trisler and coworkers (11) also have reported the synthesis of 3, 4-diphenyl-6-anisylpyridazine from cis α, ß-dibenzoylstyrene. Results and discussions: As part of our ongoing work in exploring new synthetic routes for the formation of heterocyclic compounds deriving from the condensation of hydrazine and diketones, we wish to report here a one-pot preparation of 3, 4, 6-triaryl pyridazines starting from simple and easily available starting compounds. Condensation of aryl methyl ketones with 1, 2-diketones in presence of a suitable base yielded but-2-ene-l, 4dione system as the intermediate which was then further treated with hydrazine hydrate in one pot (sheme-1) to give the expected products (12) in good yields (Table-1). The generality of the procedure was successfully demonstrated when 2-acetyl naphthalene and furil similarly underwent cyclisation to the corresponding heterocyclic compounds.(Table-2 and 3). The reactions proceeded smoothly at room temperature and the products were formed in comparatively shorter reaction time. Earlier reports have also shown similar cyclisation (13) leading to the formation of pyridazines and pyridazinones starting from 1, 4-dicarbonyl compounds. However in all these reactions the reactive intermediates were first isolated before proceeding to the next reaction. Isolation and analysis of one of the reaction intermediate (Ar =Ar =Ar=Ph) confirmed the formation of the condensed product, but-2-ene-l, 4-dione with the trans isomer (m pt 197°C) (6) predominating over the cis isomer (m pt 129°C).(6) However high yields of the products indicate that there is isomerisation around the double bond before cyclisation takes place under basic medium. This is known to occur in α , ß-unsaturated carbonyls. (13) Thus when aryl methyl ketones and 1, 2 diketones were condensed in presence of sodium tertiary butoxide in benzene and the resultant mixture treated with ethanol, subsequent treatment with hydrazine hydrate gave 3, 4, 6-triaryl pyridazines in good to excellent yields.