Hiriyakkanavar Ila

Regio- and Chemoselective Metalation of Arenes and Heteroarenes Using Hindered Metal Amide Bases

The preparation of highly functionalized organometallic compounds can be achieved by direct C-H activation of a broad range of unsaturated substrates using lithium chloride solubilized 2,2,6,6-tetramethylpiperidide bases (TMP(n)MX(m)⋅p LiCl). These are excellent reagents for converting a wide range of aromatic and heterocyclic substrates into valuable organometallic reagents with broad applications in organic synthesis.

Efficient routes to pyrazolo[3,4-b]indoles and pyrazolo[1,5-a]benzimidazoles via palladium- and copper-catalyzed intramolecular C-C and C-N bond formation

Efficient synthetic routes to pyrazolo[3,4-b]indoles and pyrazolo[1,5-a]benzimidazoles via intramolecular palladium- and copper-catalyzed cyclization of 1-aryl/1-unsubstituted 5-(2-bromoanilino)pyrazole precursors via intramolecular C-C and C-N bond formation have been reported.

Functionalized magnesium organometallics as versatile intermediates for the synthesis of polyfunctional heterocycles.

In the last few years, we have demonstrated that the halogen/magnesium-exchange reaction is a unique method for preparing a variety of new functionalized aryl, alkenyl, heteroaryl magnesium compounds which has considerably extended the range of functionalized Grignard reagents available for synthetic purposes. A variety of functional groups such as an ester, nitrile, iodide, imine and even sensitive groups like nitro, hydroxyl and boronic ester can be tolerated in these organomagnesium compounds. We wish to describe the application of this halogen/magnesium-exchange reaction for the preparation of a broad range of five- and six-membered functionalized heteroaryl magnesium compounds and their reactions with various electrophiles providing a new entry to a range of polyfunctional heterocycles such as thiophene, furan, pyrrole, imidazole, thiazole, antipyrine, pyridine, quinoline and uracil derivatives.

Novel Route to 2,3-Substituted Benzo[b]thiophenes via Intramolecular Radical Cyclization⧧

A novel route to 2,3-substituted benzo[b]thiophenes by intramolecular radical cyclization of polarized ketene dithioacetals derived from o-bromoarylacetonitriles or the corresponding 3-(methylthio)-3-alkyl/aryl/heteroaryl analogues has been reported.

Cyclocondensation of arylhydrazines with 1,3-bis(het)arylmonothio-1,3-diketones and 1,3-bis(het)aryl-3-(methylthio)-2-propenones: synthesis of 1-aryl-3,5-bis(het)arylpyrazoles with complementary regioselectivity.

Two efficient highly regioselective routes for the synthesis of unsymmetrically substituted 1-aryl-3,5-bis(het)arylpyrazoles with complementary regioselectivity starting from active methylene ketones have been reported. In the first protocol, the newly synthesized 1,3-bis(het)aryl-monothio-1,3-diketone precursors (prepared by condensation of active methylene ketones with het(aryl) dithioesters in the presence of sodium hydride) were reacted with arylhydrazines in refluxing ethanol under neutral conditions, furnishing 1-aryl-3,5-bis(het)arylpyrazoles 7, in which the het(aryl) moiety attached to the thiocarbonyl group of monothio-1,3-diketones is installed at the 3-position. In the second method, the corresponding 3-(methylthio)-1,3-bis(het)aryl-2-propenones (prepared in situ by base-induced alkylation of 1,3-monothiodiketones) were condensed with arylhydrazines in the presence of potassium tert-butoxide in refluxing tert-butyl alcohol, yielding 1-aryl-3,5-bis(het)arylpyrazoles 9 with complementary regioselectivity (method A). The efficiency of this protocol was further improved by developing a one-pot, three-component procedure for the synthesis of pyrazoles 9, directly from active methylene ketones, by reacting in situ generated 3-(methylthio)-1,3-bis(het)aryl-2-propenones with arylhydrazines in the presence of sodium hydride (instead of potassium tert-butoxide as base). The structures and regiochemistry of newly synthesized pyrazoles were confirmed from their spectral and analytical data along with X-ray crystallographic data of three pairs of regioisomers.

4-Bis(methylthio)methylene-2-phenyloxazol-5-one: versatile template for synthesis of 2-phenyl-4,5-functionalized oxazoles.

4-Bis(methylthio)methylene-2-phenyloxazol-5-one has been shown to be a versatile template for the synthesis of various 2-phenyl-3,4-substituted oxazoles via nucleophilic ring-opening of oxazolone with various oxygen, nitrogen, and carbon nucleophiles and subsequent 5-endo cyclization of the resulting acyclic adducts in the presence of silver carbonate.

1-(Methyldithiocarbonyl)imidazole: a Useful Thiocarbonyl Transfer Reagent for Synthesis of Substituted Thioureas

1-(Methyldithiocarbonyl)imidazole 1 and its N-methyl quaternary salt 2 have been shown to be efficient methyldithiocarbonyl and thiocarbonyl transfer reagents for the synthesis of dithiocarbamates, symmetrical and unsymmetrical mono-, di- and tri-substituted thioureas in high yields under mild and simple non-hazardous reaction conditions.

Keten dithioacetals. Part 11. Reaction of 3-cyano-4-methylthio-2(1H)-pyridones with hydrazine and guanidine: synthesis of novel substituted and fused pyrazolo[4,3-c]pyridone and pyrido[4,3-d]pyrimidine derivatives

The N-methylpyridones (2a–f) were prepared by alkylation of the pyridones (1a–f) with dimethyl sulphate, followed by heating the mixture of N-methyl (2) and O-methyl (3) products with methyl iodide. The pyridone (4c), the quinolone (4d) and the benzoquinolone (5b) derivatives were prepared in the same manner. Treatment of the pyridones (2a–f) and (1a–i) with hydrazine in refluxing propan-2-ol yielded the respective pyrazolo-[4,3-c]pyridone derivatives (7a–o) in excellent yields, and the fused pyridones (4a–e) and (5a–d) afforded the respective fused pyrazolopyridone derivatives (8a–e) and (9a–d) in excellent yields under identical conditions. The reactions of the N-methylpyridones (2a–f), (4c–d), and (5b) with guanidine in the presence of 2 mol of sodium ethoxide similarly gave substituted and fused pyrido [4,3-d]pyrimidine derivatives (11a–f), (12a–b), and (13), respectively.

An expeditious synthesis of substituted and annelated pyrido[2,3-b]indoles

An efficient and versatile synthesis of substituted and annelated pyrido[2,3-b]indoles (α-carboline) involving conjugate displacement on α-oxoketene dithioacetals by 1-methyl-2-oxoindole enolate anion and subsequent cyclization of the adducts in the presence of ammonium acetate has been described.

Hydrogen Peroxide/Boric Acid: An Efficient System for Oxidation of Aromatic Aldehydes and Ketones to Phenols

Hydrogen peroxide activated by boric acid in the presence of sulfuric acid has been shown to be an efficient oxidizing system for direct conversion of aromatic aldehydes and ketones to phenols.