One-pot synthesis of novel 2,3-dihydro-1H-indazoles

A copper(I)-mediated one-pot synthesis of 2,3-dihydro-1H-indazole heterocycles has been developed. This synthetic route provides the desired indazoles in moderate to good yields (55%-72%) which are substantially better than those achievable with an alternative two-step reaction sequence. The reaction is tolerant of functionality on the aromatic ring.     

Regioselective synthesis of 1-alkyl- or 1-aryl-1H-indazoles via copper-catalyzed cyclizations of 2-haloarylcarbonylic compounds

[reaction: see text] A general method for the one-step regioselective synthesis of 1-alkyl- or 1-aryl-1H-indazoles from ortho-halogenated alkanoylphenones, benzophenones, and arylcarboxylic acids, via copper-catalyzed amination, was developed by using 0.2% mol of CuO in the presence of K(2)CO(3). The reaction involves amination followed by intramolecular dehydration. Different functionalized alkyl aryl ketones, diaryl ketones, and benzoic acid derivatives were efficiently coupled with several hydrazines. Ligands commonly employed as catalysts for intermolecular amination were shown to be ineffective for this cyclization.     

A method for the regioselective synthesis of 1-alkyl-1H-indazoles

A method for the regioselective synthesis of 3-unsubstituted 1-alkyl-1H-indazoles, starting with 2-halobenzonitriles and N-alkylhydrazines, is described. The two-step reaction pathway proceeds through the intermediacy of 1-alkyl-3-amino-1H-indazoles followed by reductive deamination.     

Efficient and regioselective synthesis of 2-alkyl-2H-indazoles

An efficient and regioselective synthesis of 2-methyl-2H-indazoles and 2-ethyl-2H-indazoles using trimethyloxonium tetrafluoroborate or triethyloxonium hexafluorophosphate is reported.     

One-pot synthesis of 1-hydroxymethylene-1,1-bisphosphonate partial esters

A selective one-pot procedure of synthesis of 1-hydroxymethylene-1,1-bisphosphonic partial trimethylesters and P,P-, P,P′-diesters was described.     

Biaryl synthesis via palladium-catalyzed aryne multicomponent coupling

Aryl iodides have been introduced as electrophiles in the three-component Heck coupling of arynes. Following optimization studies to favor three- versus two-component coupling, the reaction proceeds in good yield to afford a variety of functionalized biaryls.     

Stereoselective synthesis of P-chirogenic dibenzophosphole-boranes via aryne intermediates

A new aryne-mediated tandem cross-coupling/P-cyclization sequence starting from tertiary phosphine-boranes and 1,2-dibromobenzenes is reported. P-chirogenic dibenzophospholes become accessible in a regio-, chemo-, and diastereoselective way.     

Highly efficient route to fused polycyclic aromatics via palladium-catalyzed aryne annulation by aryl halides

Polycyclic aromatic and heteroaromatic hydrocarbons have been synthesized in high yield by two different processes involving the Pd-catalyzed annulation of arynes. The first process involves a Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides. The second process utilizes a Pd-catalyzed double annulation of arynes by simple aryl halides. Both processes appear to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products.     

A synthesis of isoindoles and isoindolines via aryne intermediates

The intramolecular cyclization of the tertiary amines (3) with potassium amide in liquid ammonia affords a variety of unsymmetrical isoindolines (5) and isoindoles (6).     

Solid-phase synthesis of heterocycles via palladium-catalyzed annulation

Solid-phase linked o-iodoanilines (4) and o-iodophenol (9) reacted with 1,3- and 1,4-dienes in the presence of palladium acetate to generate highly substituted indolines, tetrahydroquinolines, hydrobenzofurans and hydrobenzopyrans, which provided an efficient way for making heterocyclic molecule libraries.     

Facile palladium-catalysed synthesis of 1-aryl-1H-indazoles from 2-bromobenzaldehydes and arylhydrazines

2-Bromobenzaldehydes react with arylhydrazines in toluene at 100 [degree]C in the presence of a catalytic amount of a palladium catalyst and phosphorus chelating ligands such as 1,1[prime or minute]-bis(diphenylphosphino)ferrocene and 1,3-bis(diphenylphosphino)propane along with NaO-t-Bu to afford 1-aryl-1H-indazoles in good yields.     

Simple and efficient synthesis of substituted 1H-indazoles

3-Aryl-5-aroylindazoles were prepared by a simple two-stage protocol from 3,5-diaroyl-2,6-dimethylpyridines.     

One-pot synthesis of 2,4-disubstituted quinolines via silver-catalyzed three-component cascade annulation of amines,alkyne esters and terminal alkynes

Described herein is a new and general method for one-pot synthesis of 2,4-disubstituted quinolines via silver-catalyzed [3?+?1?+?2] annulation of simple amines, alkyne esters and terminal alkynes. The versatile transformation might initiate with the facile formation of the enamine species with the feature of good to excellent yields, exclusive regioselectivity, and excellent substrate/functional group tolerance.     

One-pot synthesis of indole-fused scaffolds via gold-catalyzed tandem annulation reactions of 1,2-bis(alkynyl)-2-en-1-ones with indoles

The gold-catalyzed tandem cyclization of 1,2-bis(alkynyl)-2-en-1-ones with indoles offers an efficient and straightforward route to indole-fused polycyclic systems. The process is realized through a cascade carbonyl-yne cyclization/Friedel-Crafts/indole-yne cyclization sequence catalyzed by a single-pot catalyst of gold.     

A practical, metal-free synthesis of 1H-indazoles

The synthesis of 1H-indazoles is achieved from o-aminobenzoximes by the selective activation of the oxime in the presence of the amino group. The reaction occurs with a variety of substituted o-aminobenzoximes using a slight excess of methanesulfonyl chloride and triethylamine at 0-23 degrees C and is amenable to scale-up. The synthesis of 1H-indazoles under these conditions is extremely mild compared with previous synthetic approaches and affords the desired compounds in good to excellent yields.     

1-Alkylpyrazoles and 1-alkyl-5-chloropyrazoles from halovinyl ketones and 1,1-dialkylhydrazines

Regioselective heterocyclization of alkyl 2-chloro-and 2,2-dichlorovinyl ketones with 1,1-dialkyl-hydrazines to 1,3-dialkyl-1H-pyrazoles and 1,3-dialkyl-5-chloro-1H-pyrazoles involves intermediate formation of the corresponding dialkylhydrazones. Fragmentation pattern of chlorine-containing pyrazoles, 3-chloromethyl-1-methyl-1H-pyrazole and 5-chloro-1-methyl-3-propyl-1H-pyrazole, depends on the position of the halogen atom.     

Stereoselective total synthesis of aminoiminohexitols via carbamate annulation

New methodology for the preparation of a variety of aminoiminohextitols is described. Key in the synthesis is the application of a diastereoselective Strecker reaction and the extension of our carbamate annulation methodology to protected and functionalized alkenylamines. Insight into the effects that the substitution patterns of the alkenylamines have on the diastereoselectivity of the iodocyclization and carbamate annulation is discussed. An evaluation of the glycosidase inhibitory activity of the aminoiminohexitols and derivatives is also presented, with the previously undisclosed D-talo isomer showing good selective inhibition of β-D-glucosidase.     

One-pot synthesis of diarylimidazolium salts from 1H-imidazole

Diarylimidazolium salts(3) were directly synthesized starting from 1H-imidazole(1) by a one-pot strategy using diaryliodonium salts as the arylating reagents.1H-Benzimidazole and 1H-1,2,4-triazole are suitable substrates as well to form the corresponding diarylazolium salts.     

One-pot synthesis of carbohydrate thionolactones from 1-thiosugars

A general and efficient one-pot method for the synthesis of carbohydrate thionolactones from the corresponding 1-thiosugar is described involving the formation of an intermediate glycosyl S-tert-butyl thiosulfinate in situ by treatment of a thiol with commercially available tert-butylsulfinyl chloride in toluene at room temperature, followed by thermolysis. The method can also be used to generate reactive thioaldehydes and thioketones directly from thiols, which can be trapped in situ with a suitable diene.