Siva Murru

Copper(I)-Catalyzed Synthesis of Substituted 2-Mercapto Benzimidazoles

An efficient method for the preparation of various substituted 2-mercapto benzimidazoles from their corresponding thioureas has been developed. S-alkylation of thioureas followed by Cu-catalyzed intramolecular N-arylation furnished substituted 2-mercapto benzimidazoles in high yields and short reaction times. Furthermore, 2-mercapto benzimidazoles substituted with a p-methoxybenzyl group allowed access to benzimidazole thiones.

Intra- and Intermolecular C−S Bond Formation Using a Single Catalytic System: First Direct Access to Arylthiobenzothiazoles

We have for the first time developed two ligand-assisted Cu(I)-catalyzed sequential intra- and intermolecular S-arylations leading to the direct synthesis of arylthiobenzothiazoles in one pot without an inert atmosphere. Low catalyst loading, inexpensive metal catalyst and ligand, lower reaction temperature, and shorter reaction times make this method superior to all reported methods for the synthesis of arylthiobenzothiazole.

Hypervalent Iodine(III)-Mediated Regioselective N-Acylation of 1,3-Disubstituted Thioureas

Reaction of asymmetrical 1,3-disubstituted thioureas with diacetoxyiodobenzene (DIB) produces regioselectively N-acetylurea in shorter time. Regioselectivity is dependent on the pKas of the amine attached to the thiourea moiety with acylation taking place toward the amine having a lower pKa. This is the first example of DIB being employed as an N-acetylating agent. A mechanism for this novel transformation is also proposed. Mild reaction conditions, shorter reaction times, high efficiencies, environmentally benign methods, and facile isolation of the desired product make the present methodology a most suitable alternative.

Acyl-isothiocyanates as Efficient Thiocyanate Transfer Reagents

An unprecedented transfer of a thiocyanate (-SCN) group from aroyl/acyl isothiocyanate to alkyl or benzylic bromide is observed in the presence of a tertiary amine. This process is most effective when the bromomethyl proton is less acidic, while the presence of a more acidic proton gives 1,3-oxathiol-2-ylidine and other related products.

Combinatorial Synthesis of Oxazol-Thiazole Bis-Heterocyclic Compounds

A combinatorial library of novel oxazol-thiazole bis-heterocycles was synthesized in good to excellent overall yields with high purity using a solution and solid-phase parallel synthesis approach. Oxazole amino acids, prepared from serine methyl ester and amino acids via coupling and cyclodehydration, were treated with Fmoc-NCS and α-haloketones for the parallel synthesis of diverse bis-heterocycles. Fmoc-isothiocyanate is used as a traceless reagent for thiazole formation. Oxazole diversity can be achieved by using variety of amino acids, whereas thiazole diversity is produced with various haloketones.

Fe-Catalyzed Direct α C–H Amination of Carbonyl Compounds

A direct Fe-catalyzed α-amination of 1,3-dicarbonyl compounds has been accomplished using arylhydroxylamines as aminating agents. This novel protocol allows convenient access to α-amino carbonyl derivatives without the need for any postreaction manipulations. This is an operationally simple procedure that works at low temperatures in shorter reaction times and produces high yields with excellent N-selectivity.

Efficient Preparation of Isothiocyanates From Dithiocarbamates Using Bromineless Brominating Reagent

For the first time, the crystal structure of a ditribromide reagent 1,1′-(ethane-1,2-diyl)dipyridinium bistribromide (EDPBT) has been determined. Utilizing this thiophilic bromineless brominating agent EDPBT, highly useful synthetic intermediates (alkyl and aryl isothiocyanates) have been achieved directly from dithiocarbamates. EDPBT can be easily prepared from readily available reagents. It has been used as a thiophilic reagent, and its thiophilicity dominates over its brominating ability for substrates amenable to bromination. This is a sustainable process for the preparation of isothiocyantes because the spent reagent can be recovered, regenerated, and reused.

Direct Synthesis of β-Alkyl N-Aryl Aza Baylis–Hillman Adducts via Nitroso-Ene Reaction

A new approach for the direct Fe-catalyzed synthesis of β-alkyl N-aryl aza Baylis-Hillman (ABH) adducts is reported. This approach involves the formation of a C-N bond via a nitroso-ene reaction. This is a simple, fast, and best alternate method to overcome the substrate scope limitations of the ABH reaction, which converts allyl esters and carbonyl compounds to novel ABH adducts. A variety of arylhydroxylamines reacted with esters, aldehydes, ketone, and nitriles to yield the corresponding products in moderate to excellent yields.

3 -aryl-1-benzoylthioureas with α-bromoketones in water form 2-N-benzoyl-3-arylthiazol -2 (3H)-imines, not 3-aryl-1 -benzoylimidazoline-2-thiones

The products obtained by the reaction of 1-benzoyl-3-phenylthioureas with α-bromoketones in water in the presence of triethylamine are not imidazoline-2-thiones as reported (J. Chem. Res. 2005, 689–690); rather they are thiazol-2-imine derivatives.

Ru(III)–TMSO complexes containing azole-based ligands: synthesis and cytotoxicity study

The reaction of mer-[RuCl3(S-TMSO)2(O-TMSO)] (TMSO = tetramethylene sulfoxide) with azoles (pyrazole = pzH and 3,5-dimethylpyrazole = dmpzH) in dichloromethane produced the complexes mer-[RuCl3(S-TMSO)(pzH)2] 1, mer-[RuCl3(S-TMSO)(O-TMSO)(pzH)] 2, mer-[RuCl3(S-TMSO)(dmpzH)2] 3, and mer-[RuCl3(S-TMSO)(O-TMSO)(dmpzH)] 4. These complexes were characterized using analytical, spectroscopic, and electrochemical techniques, as well as single-crystal X-ray diffraction analysis. Cytotoxicity assays on NB-Nu-39, a human neuroblastoma cell line, revealed that compounds 3 and 4, bearing methyl groups at the 3- and 5-positions of the pyrazole ring, exhibited significant cytotoxic activity towards neuroblastoma cells with IC50 values of 14.5 μM and 12.9 μM, respectively. The IC50 value of NAMI-A was 12.4 μM, which is very close to that of 4. In contrast, compounds 1 and 2 exhibited no appreciable cytotoxic activity towards neuroblastoma cells (IC50 ≫ 100 μM). The lipophilicity of complexes 1–4 was measured by the shake-flask method to obtain the partition coefficient. These studies reveal that lipophilicity may be a determining factor in the anticancer activity and pharmacological behavior of these Ru(III) complexes.