Sundaravel Vivek Kumar

A solvent- and catalyst-free domino reaction for the efficient synthesis of 3-arylthiazolidine-2-thiones under microwave irradiation

A facile synthesis of 4-hydroxy-3-arylthiazolidine-2-thiones through novel domino reactions of aryl isothiocyanates and 1,4-dithiane-2,5-diol under solvent- and catalyst-free microwave irradiation is reported. This highly atom efficient reaction presumably proceeds via 2-mercaptoacetaldehyde generation/thia-Michael addition/regioselective hemiaminalization domino sequence. This reaction also proceeds in good yields with aryl isocyanates affording 3-phenylthiazol-2(3H)-ones.

An efficient synthesis of N-substituted 3-nitrothiophen-2-amines.

Summary A novel protocol for the synthesis of 3-nitro-N-aryl/alkylthiophen-2-amines in good yields from the reaction of α-nitroketene N,S-aryl/alkylaminoacetals and 1,4-dithiane-2,5-diol in the presence of K2CO3 in refluxing ethanol is described. This transformation generates two C–C bonds in a single operation and presumably proceeds through a reaction sequence comprising 2-mercaptoacetaldehyde generation, nucleophilic carbonyl addition, annelation and elimination steps.

One-Pot Access to a Library of Dispiro Oxindole-pyrrolidine/pyrrolothiazole-thiochromane Hybrids via Three-Component 1,3-Dipolar Cycloaddition Reactions

A library of novel dispiro compounds containing oxindole pyrrolidine/oxindolopyrrolothiazole-thiochroman-4-one hybrid frameworks has been synthesized in a fully regio- and stereoselective fashion by the three-component 1,3-dipolar cycloaddition of azomethine ylides generated in situ from the condensation of isatins and secondary amino acids (sarcosine/l-thioproline) with 3-arylidenethiochroman-4-ones. This experimentally simple protocol provides good yields of structurally complex, biologically relevant heterocycles in a single operation.

Facile “on water” domino reactions for the expedient synthesis of 2H-thiopyrano[2,3-b]quinolines

A facile synthesis of novel 3-nitro-2-aryl-2H-thiopyrano[2,3-b]quinolines from the domino reactions of 2-mercaptoquinoline-3-carbaldehyde and substituted β-nitrostyrenes in the presence of triethylamine (TEA) in water is described. This “on water” protocol proceeds with high atom economy through the creation of one C–S and one C–C bond presumably via a Michael addition-intramolecular aldol-dehydration domino sequence.

A facile stereoselective synthesis of dispiro-indeno pyrrolidine/pyrrolothiazole-thiochroman hybrids and evaluation of their antimycobacterial, anticancer and AchE inhibitory activities.

A facile stereoselective synthesis of novel dispiro indeno pyrrolidine/pyrrolothiazole-thiochroman hybrids has been achieved by 1,3-dipolar cycloaddition of azomethine ylides, generated in situ from ninhydrin and sarcosine/thiaproline, on a series of 3-benzylidenethiochroman-4-ones. The synthesised compounds were screened for their antimycobacterial, anticancer and AchE inhibition activities. Compound 4l (IC50 1.07μM) has been found to exhibit the most potent antimycobacterial activity compared to cycloserine (12 times), pyrimethamine (37 times) and ethambutol (IC50 <1.56μM) and 6l (IC50=2.87μM) is more active than both cycloserine (4 times) and pyrimethamine (12 times). Three compounds, 4a, 6b and 6i, display good anticancer activity against CCRF-CEM cell lines. Compounds 6g and 4g display maximum AchE inhibitory activity with IC50 values of 1.10 and 1.16μmol/L respectively.

Synthesis of novel 16-spiro steroids: 7-(Aryl)tetrahydro-1H-pyrrolo[1,2-c][1,3]thiazolo estrone hybrid heterocycles.

The 1,3-dipolar cycloaddition of azomethine ylides generated in situ from the reaction of isatins or acenaphthylene-1,2-dione and 1,3-thiazolane-4-carboxylic acid to various exocyclic dipolarophiles synthesized from estrone afforded a library of novel C-16 spiro oxindole or acenaphthylene-1-one - 7-(aryl)tetrahydro-1H-pyrrolo[1,2-c][1,3]thiazole - estrone hybrid heterocycles. These reactions occur regio- and stereo-selectively affording a single isomer of the spiro estrones in excellent yields with the formation of two C-C and one C-N bonds along with the generation of four new contiguous stereo-centers in a single step.

A One-Pot Multicomponent 1,3-Dipolar Cycloaddition Strategy: Combinatorial Synthesis of Dihydrothiophenone-Engrafted Dispiro Hybrid Heterocycles

The combinatorial syntheses of a library of novel dihydrothiophenone-engrafted dispiro oxindole/indenoquinoxaline-pyrrolidine/pyrrolothiazole/indolizine hybrid heterocycles have been realized through a chemo-, regio-, and stereoselective multicomponent 1,3-dipolar cycloaddition strategy.

Synthesis of highly functionalized 2-thiaspiro[4.5]deca-6,8-dienes via atom efficient tandem Michael addition/Thorpe–Ziegler cyclization

The two-component reaction of 2,4-bis((Z)-arylidene)dihydrothiophen-3(2H)-ones and 2-(1-arylethylidene)malononitriles proceeded through a tandem chemoselective Michael addition–tautomerization–Thorpe–Ziegler cyclization sequence of reactions in a single step affording novel 2-thiaspiro[4.5]deca-6,8-dienes in quantitative yields.

A facile solvent-free three-component domino synthesis of novel 2,4-diaryl-5,6-dihydrobenzo[j][1,7]phenanthrolines

A simple, efficient and green procedure for the synthesis of novel 2,4-diaryl-5,6-dihydrobenzo[j][1,7]phenanthrolines has been developed via a Krohnke-type one-pot three-component reaction of 2-[arylmethylidene]-3,4-dihydro-1(2H)-acridinones and (2-aryl-2-oxoethyl)pyridinium bromides in the presence of excess ammonium acetate in good yields under solvent-free conditions. Good functional group tolerance, high substrate scope and no column purification are the practical advantages of this methodology.Graphical abstract

Synthesis of penta- and tetra-cyclic cage-like compounds and dispiro heterocycles through microwave-assisted solvent-free multi-component domino reactions

Novel penta- and tetra-cyclic cage-like compounds and dispiro heterocycles were obtained as a result of the microwave-assisted three-component domino reactions of heterocyclic or carbocyclic ketones, ninhydrin and sarcosine under solvent- and catalyst-free conditions. Interestingly, heterocyclic ketones afforded fused polycyclic cage-like compounds, whereas the carbocyclic ketones led to the formation of dispiro heterocycles.