Suresh Patil

Green Approach for Knoevenagel Condensation of Aromatic Aldehydes with Active Methylene Group

Abstract An ecofriendly and economical method of Knoevenagel condensation of aromatic aldehydes with malononitrile catalyzed by lemon juice, a natural catalyst, in the absence of any solvent is described. GRAPHICAL ABSTRACT

Calcined eggshell (CES): An efficient natural catalyst for Knoevenagel condensation under aqueous condition

AbstractA convenient, eco-friendly and economic method for Knoevenagel condensation of aromatic aldehydes with active methylene compounds using calcined eggshell (CES) as an efficient natural catalyst in aqueous medium has been reported. CES is a new, ecologically safe and inexpensive green catalyst obtained from renewable resources. Graphical AbstractA convenient, eco-friendly and economic method for Knoevenagel condensation of aromatic aldehydes with active methylene compounds using CES as an efficient natural catalyst in aqueous medium has been reported here. CES is a new, ecologically safe, inexpensive and green catalyst obtained from waste eggshells.

Synthesis and antimicrobial activities of new oxime carbamates of 3-aryl-2-thioquinazolin-4(3H)-one

AbstractS-alkylation of 3-aryl-2-thioquinazolin-4(3H)-one (1) with chloroacetone gave 2-(propanonyl thio)-3-arylquinazol-4(3H)ones (2). Further, the treatment of compound (2) with hydroxylamine hydrochloride gave the corresponding oximes (3) which on reaction with phenyl isocyanate in THF yielded corresponding oxime carbamates 4. The synthesized compounds have been confirmed using IR and 1H NMR, mass spectral data together with elemental analysis. All newly synthesized compounds have been tested for their antibacterial and antifungal activities. Graphical AbstractCorresponding oxime carbamates (4) were synthesized by using 3-aryl-2-thioquinazolin-4(3H)-one (1) as starting material. This step-wise conversion involves S-alkylation of 3-aryl-2-thioquinazolin-4(3H)-one and oxime formation. The compounds have been tested for their antibacterial and antifungal activities.

Aegle marmelos in heterocyclization: greener, highly efficient, one-pot three-component protocol for the synthesis of highly functionalized 4H-benzochromenes and 4H-chromenes

A facile, one-pot three-component protocol for the synthesis of 2-amino-4H-chromene derivatives has been demonstrated using Bael Fruit Extract (BFE) as a natural catalyst in a green reaction medium. This method offers a mild, efficient and highly economical protocol since the reaction proceeds in natural BFE-catalyst at room temperature under aerobic conditions with a very short reaction time (30 min) under ligand/external catalyst/external promoter-free conditions and, therefore, it is a green and environmentally sound alternative to the existing protocols. The catalyst was obtained by thermal treatment followed by water extraction of the rind of Aegle marmelos (bael) fruit. It was also found to be clean, high-yielding and has the capacity for large scale synthesis.

Bronsted acid-type biosurfactant for heterocyclization: a green protocol for benzopyran synthesis

A natural biosurfactant, a biobased green acidic catalyst for cyclocondensation of salicylaldehyde (or 2-hydroxy naphthaldehyde) and cyclic 1,3-diketones for benzopyran synthesis in water has been reported for the first time. The structures of the final compounds were confirmed with the aid of IR, 1H NMR, and 13C NMR spectroscopy. Lemon extract as a natural biosurfactant provides a micellar media for effective organic transformation. The CMC of lemon extract was determined by the conductivity method. In comparison to the conventional methods, this synthetic pathway complies with several key requirements of green chemistry principles such as the utilization of renewable feedstock, auxiliary aqueous conditions, waste prevention, and atom economy along with the use of biodegradable catalyst. Thus, the reported protocol offers an attractive option because of its ecological safety, environmental acceptance, sustainability, and low-cost straightforward work-up procedure.

Synergistic effect of natural chickpea leaf exudates acids in heterocyclization: a greener protocol for benzopyran synthesis

Without using any toxic or hazardous reagent, ligand, acid, transition metal catalyst, additives/promoters and organic solvent, green Knoevenagel condensation and tandem Knoevenagel–Michael reactions have been successfully carried out by using chickpea leaf exudates as a naturally sourced Bronsted acid type bio-catalyst. The reaction proceeds in neat chickpea leaf exudates at room temperature in aqueous conditions in very short reaction times, and therefore, it is an evergreen and environmentally sound alternative to the existing protocols for benzopyran synthesis. In comparison to the conventional methods, this synthetic pathway complies with several key requirements of green chemistry principles such as the utilization of biodegradable catalyst obtained from renewable feedstock, auxiliary aqueous conditions, along with waste prevention. The same protocol was also extended to the synthesis of 2H-xanthene-1,8-diones by condensation of aromatic aldehydes with dimedone achieving excellent yields. Thus, the reported protocol offers an attractive option because of its ecological safety, environmental acceptance, sustainability, low-cost straightforward work-up procedure and with excellent values of green chemistry metrics as compared with other reported methods.

Synergetic effects of naturally sourced metal oxides in organic synthesis: a greener approach for the synthesis of pyrano[2,3-c]pyrazoles and pyrazolyl-4 H -chromenes

A clean and more economic protocol for the synthesis of pyrano[2,3-c]pyrazoles and pyrazolyl-4H-chromenes has been carried out using bael fruit ash (BFA) as a non-conventional natural catalyst in aqueous condition at ambient temperature. The catalyst was obtained from renewable resources by simple thermal treatment to dry rind of Aegle marmelos (Bael) fruit and formation of its active phase was confirmed by AAS, DSC-TGA, XRD, FT-IR, and SEM techniques. The BFA catalyst was found to be a green, highly active, easily biodegradable, and recyclable without loss of activity after the fifth run. The methodology provides an alternative platform to the conventional catalyzed process.Graphical Abstract

Citric acid as a mild and inexpensive organocatalyst for synthesis of tetrahydrobenzo[ a ] xanthen-11-ones and dibenzo[ a,j ] xanthenes under solvent-free condition

A simple and efficient protocol has been developed for the synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a] xanthen11-one derivatives, I employing a one-pot three-component reaction of aldehydes, 2-naphthol and dimedone in the presence of citric acid under solvent-free condition at 120°C. The protocol has been also extended for the synthesis of 14-aryl-14Hdibenzo [a.j] xanthenes, II by employing 1:2 proportion of aldehyde and 2-naphthol, to afford excellent yield in short reaction time.