Microwave assisted solvent-free synthesis and biological activities of novel imines (Schiff bases)

Abstract

Twelve new ortho-Hydroxyketimines were synthesized by conventional as well as microwave method and evaluated for their antinemic activity against Meloidogyne incognita [(Kofoid and White) Chitwood]. Conventional methods for synthesis of Schiff bases require refluxing at 140 degrees C of the reactants in different solvents for at least 24 h or more, where as the microwave-assisted synthesis has brought down the reaction time from 24 h to 1 minute. The procedure reported is simple as it does not require any organic solvents and the time has been reduced to only 1 minute. Comparative yields of all compounds by different methods revealed that the yield was low in conventional method (79-87%) as compared to microwave assisted synthesis (94-97%). The bioassay revealed that all the test compounds exhibited promising nematicidal activity; N-propyl-2-hydroxypropiophenonimine being the most effective with LC(50) value of 74.46 mgL(-1) followed by N-hexyl-2-hydroxyacetophenonimine with LC(50) value of 99.60 mgL(-1) after 72 h of exposure. The results obtained from bioassay indicated that this class of compounds has not only given a lead with regard to potential of Schiff bases in pest control, but has suggested that a carbon chain length of 6 atoms in the side chain is optimum on the basis of structure activity relationship (SAR).

Solvent-Free Synthesis and Spectral Linearity of Some (E)-2-(substituted benzylideneamino)-N-(3-chloro-4-fluorophenyl)-hexahydro-2<i>H</i>-cyclopenta[b]thiophene-3-carboxamides

“…The correlation equations are given in (19)(20)(21)(22). thiophene-3-carboxamide and various substituted benzaldehydes using microwave irradiation in the presence of SiO 2 -H 3 PO 4 catalyst under solvent free conditions.…”

“…These catalysts have been applied for the synthesis of chiral amines by oxidative coupling of amines [54,55], with carbonyl compounds [19,21,41,42] alcohols [34] and acid chlorides [38,56]. The microwave assisted synthesis has become popular in academic and pharmaceutical areas since this involves a new enabling technology for developing new drugs.…”

“…The microwave assisted synthesis has become popular in academic and pharmaceutical areas since this involves a new enabling technology for developing new drugs. Chemists and scientists [19,21,41,57,58] preferred solvent free microwave synthetic methods for synthesizing organic compounds, since they involve shorter duration, operational simplicity, easy workup procedure, less hazardousness to humans and environment, and better yields. Spectroscopic data is applied for studying the ground state equilibrium of organic molecules through linear free energy relationships [58].…”

“…Optically active imine derivatives possess multipronged biological activities such as antimicrobial [15], anticancer [16,17], antiplasmodic-antihypoxic [18], antitubularcular [19,20], nematicidal-insecticidal [21], anti-inflammatory, and lipoxygenase [22]. The imine moieties are important intermediates and versatile starting materials for the synthesis of chiral amines [23,24], pyrimidine derivatives [25], phenylhydrazones [26,27], Mannich bases [28], indoles [29], quinoxalines [30], imidazoles [31], amino triphenylmethanes [32], Michael adducts [33], allyl products [34], optically active α-alkyl aldehydes [35,36] by hydrogenation [37], nucleophilic addition with organometallics [38] and cycloaddition reaction [39].…”

(<i>E</i>)-N-Substitutedbenzylidene-4-Methoxyanilines as Insect Antifeedants

“…Optically active imine derivatives possess multipronged biological activities such as antimicrobial [15], anticancer [16], antiplasmodic-antihypoxic [17], antitubularcular [18], nematicidalinsecticidal [19], anti-inflammatory and lipoxygenase [20].…”