A Mitsunobu reaction to functionalized cyclic and bicyclic N-arylamines

The scope of an unexpected Mitsunobu cyclisation to prepare N-arylated Fsp³-enriched azacycles was investigated. In the current study, we have identified whether a pKa-dependent Mitsunobu cyclodehydration or a pKa-independent Mitsunobu intramolecular reaction was in operation. A Mitsunobu reaction, creating a leaving group, followed by intramolecular nucleophilic displacement was determined to be the dominant pathway.     

Reductive heterocyclizations via indium/iodine-promoted one-pot conversion of 2-nitroaryl aldehydes, ketones, and imines

2-Nitroaryl aldehydes, ketones, and imines were reductively cyclized to 2,1-benzisoxazoles with good yields in the presence of indium and iodine in MeOH. Under a similar condition, N-(2-nitrobenzylidene)anilines were produced mixtures of 2,1-benzisoxazoles and 3-anilino-2-phenyl-2H-indazoles.     

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.     

Ionic diamine rhodium complex catalyzed reductive N-heterocyclization of N-(2-nitroarylidene)amines

Ionic diamine rhodium complexes catalyze the reductive N-heterocyclization of N-(2-nitroarylidene)amines under carbon monoxide to afford the corresponding 2H-indazoles in up to 75% yields.     

Synthesis and Characterization of Novel Methyl (3)5-(N-Boc-piperidinyl)-1H-pyrazole-4-carboxylates

Series of methyl 3- and 5-(N-Boc-piperidinyl)-1H-pyrazole-4-carboxylates were developed and regioselectively synthesized as novel heterocyclic amino acids in their N-Boc protected ester form for achiral and chiral building blocks. In the first stage of the synthesis, piperidine-4-carboxylic and (R)- and (S)-piperidine-3-carboxylic acids were converted to the corresponding β-keto esters, which were then treated with N,N-dimethylformamide dimethyl acetal. The subsequent reaction of β-enamine diketones with various N-mono-substituted hydrazines afforded the target 5-(N-Boc-piperidinyl)-1H-pyrazole-4-carboxylates as major products, and tautomeric NH-pyrazoles prepared from hydrazine hydrate were further N-alkylated with alkyl halides to give 3-(N-Boc-piperidinyl)-1H-pyrazole-4-carboxylates. The structures of the novel heterocyclic compounds were confirmed by ¹H-, ¹³C-, and ¹⁵N-NMR spectroscopy and HRMS investigation.     

Microwave-assisted synthesis of 1-aryl-1H-indazoles via one-pot two-step Cu-catalyzed intramolecular N-arylation of arylhydrazones

A highly efficient one-pot two-step microwave procedure was developed for the synthesis of 1-aryl-1H-indazoles. Microwave heating of 2-halobenzaldehydes or 2-haloacetophenones with phenylhydrazines at 160 °C for 10 min quantitatively yielded the arylhydrazones, which were further cyclized to give 1-aryl-1H-indazoles via CuI/diamine-catalyzed N-arylation under microwave heating (160 °C, 10 min). Good to excellent yields were observed for 2-iodo, 2-bromo, and 2-chloro benzaldehydes or acetophenones.     

BF3·Et2O promoted one-pot expeditious and convenient synthesis of 2-substituted benzimidazoles and 3,1,5-benzoxadiazepines

2-Substituted benzimidazoles and 3,1,5-benzoxadiazepines have been synthesized in excellent yields in a single pot by cyclodehydration of N-acyl-1,2-phenylenediamines and N,N^′-diacyl-1,2-phenylenediamines prepared in situ from the corresponding 1,2-phenylenediamines and an acid chloride, respectively.     

Synthesis,structure, and antimicrobial activity of methyl (4-alkanoyl-1,5-diaryl-2-hydroxy-3-oxo-2,3-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrrol-2-yl)acetates

Reactions of methyl 3,4,6-trioxoalkanoates (3,4-dihydroxy-6-oxo-2,4-alkadienoates) with mixtures of aromatic aldehydes and arylamines or with the corresponding N-(arylmethylidene)anilines afforded methyl (4-alkanoyl-1,5-diaryl-2-hydroxy-3-oxo-2,3-dihydro-1H-pyrrol-2-yl)acetates. The product structure was discussed on the basis of their IR, ¹H NMR, and mass spectra and X-ray diffraction data, and their antimicrobial activity against Staphylococcus aureus P-209 and Escherichia coli M₁₇ was evaluated.     

Regiospecificity of nucleophilic substitution in 4,6-dinitro-1-phenyl-1H-indazole

The reactions of 4,6-dinitro-1-phenyl-1H-indazole with anionic nucleophiles RS^– and N₃ ^– lead to the regiospecific replacement of the nitro group at position 4. The reaction with N₂H₄·H₂O + FeCl₃ also results in reduction of only the 4-NO₂ group. Based on this fact, a procedure was developed for the preparation of previously unknown 3-unsubstituted 4-X-6-nitro-1-phenyl-1H-indazoles (X is a residue of a nucleophile or NH₂). Comparison of the data on the selective nucleophilic substitution (4-NO₂ group) in 3-Z-1-aryl-4,6-dinitro-1H-indazoles shows that in the case of Z = H, the regiospecificity of substitution is determined by the electronic effect of the annelated pyrazole ring.     

Rhodium(III)-catalysed,redox-neutral C(sp2)-H alkenylation using pivalimide as a directing group with internal alkynes

In the presence of [RhCp¹Cl₂]₂, N-pivaloyl anilines react with internal alkynes to give the corresponding 2-alkenylpivalimides under redox neutral conditions through C-H activation. This redox neutral hydroarylation, which does not require an external organic acid, unlocks a regioselective synthetic route to 2-alkenyl anilines and is generally applicable to diversely substituted electron rich and electron poor pivalimides.     

Rh(III)-catalyzed [4 + 1]-annulation of azobenzenes with α- carbonyl sulfoxonium ylides toward 3-acyl-(2H)-indazoles

A Rh(III)-catalyzed [4?+?1]-annulation of azobenzenes with α- carbonyl sulfoxonium ylides was developed to access 2H-indazoles in moderate to excellent yields with good functional group compatibilities. It proceeded with the sequential insertion of the Rh(III) carbene to the C?H bond and cyclization steps, where sulfoxonium ylides served as efficient and stable carbene precursor.     

Synthesis,In Silico and In Vitro Evaluation of Antimicrobial and Toxicity Features of New 4-[(4-Chlorophenyl)sulfonyl]benzoic Acid Derivatives

The multi-step synthesis, physico-chemical characterization, and biological activity of novel valine-derived compounds, i.e., N-acyl-α-amino acids, 1,3-oxazol-5(4H)-ones, N-acyl-α-amino ketones, and 1,3-oxazoles derivatives, bearing a 4-[(4-chlorophenyl)sulfonyl]phenyl moiety are reported here. The structures of the newly synthesized compounds were confirmed by spectral (UV-Vis, FT-IR, MS, ¹H- and ¹³C-NMR) data and elemental analysis results, and their purity was determined by RP-HPLC. The new compounds were assessed for their antimicrobial activity and toxicity to aquatic crustacean Daphnia magna. Also, in silico studies regarding their potential mechanism of action and toxicity were performed. The antimicrobial evaluation revealed that the 2-{4-[(4-chlorophenyl)sulfonyl]benzamido}-3-methylbutanoic acid and the corresponding 1,3-oxazol-5(4H)-one exhibited antimicrobial activity against Gram-positive bacterial strains and the new 1,3-oxazole containing a phenyl group at 5-position against the C. albicans strain.     

An efficient, greener, and solvent-free one-pot multicomponent synthesis of 3-substituted quinazolin-4(3H)ones and thienopyrimidin-4(3H)ones

Herein, we report an efficient, greener, and solvent-free novel method for the synthesis of 3-substituted quinazolin-4(3H)ones and thienopyrimidin-4(3H)ones in a one-pot sequence using methyl anthranilate or 2-aminothiophene-3-carboxylate with N,N′-dimethyl formamide dimethyl acetal and various anilines. The driving force for this reaction is the removal of N,N′-dimethylamine by various anilines resulting in 3-substituted quinazolin-4(3H)ones and thienopyrimidin-4(3H)ones.     

Pd- and Cu-catalyzed C–H arylation of indazoles

The palladium- and copper-catalyzed C–H arylation reactions of 1H- and 2H-indazoles with haloarenes are described. A PdCl₂/phen/Ag₂CO₃/K₃PO₄ catalytic system is effective for the C–H arylation of 1H- and 2H-indazoles with haloarenes, whereas a less expensive CuI/phen/LiOt-Bu catalytic system is applicable to the C–H coupling of substituted 2H-indazoles and iodoarenes. The utility of newly developed catalyst was demonstrated in the rapid synthesis of YC-1 (an antitumor agent) and YD-3 (platelet anti-aggregating agent). These new reactions represent important direct functionalization tools of indazoles, well-known bioisosteres of pharmaceutically important indole core.     

Chemistry of iminofurans: XII.<Superscript>1</Superscript> Synthesis of 2-(arylimino)furan-3(2<Emphasis Type="Italic">H</Emphasis>)-ones and their reaction with amines

2-(Arylimino)-5-(het)arylfuran-3(2H)-ones were synthesized by reaction of 5-(het)arylfuran-2,3-diones with N-(triphenyl-λ⁵-phosphanylidene)anilines, and their aminolysis afforded N-aryl-4-amino-4-(het)aryl-2-oxobut-3-enamides.     

Benzo[7,8]indolizinoquinoline scaffolds based on Mg(ClO4)2-promoted regiospecific imide reduction and π-cyclization of N-acyliminium species. Analogues of the topo-1 poison rosettacin and 22-hydroxyacuminatine alkaloids

A general five-step synthesis of a short library of benzo[7,8]indolizinoquinolinine analogues of the topoisomerase-1 (topo-1) poison rosettacin and 22-hydroxyacuminatine alkaloids from DMAD and ortho-ketoanilines is reported. This consists on successively, the tandem aza-Michael addition/cyclodehydration, the hydrolysis of the resulting diesters into corresponding o-dicarboxylic acids, and the tandem intermolecular amidation/cyclodehydration into N-substituted imides. The regioselective reduction of one imide carbonyl into corresponding α-hydroxy lactams promoted by a Lewis acid Mg(ClO₄)₂ was followed ultimately with TFA-promoted π-cationic cyclization via stable N-acyliminiums species as an important key step.     

Solid-phase synthesis of tertiary-amino linked benzamides: a versatile method for forming C-N bonds with electron-rich and electron-poor anilines

There currently are a wide variety of methods for forming C-N bonds on solid support. Two preferred methods are reductive aminations with resin bound amines or aldehydes as well as standard alkylation strategies. We herein disclose the scope and application of the Mitsunobu reaction of 2,4-dinitro-N-phenylbenzenesulfonamides derived from both electron-rich and electron-poor anilines as a practical and versatile addition to the repertoire of solid phase C-N bond forming reactions.     

The reaction of 4-alkyl-3-thiosemicarbazides with β-haloketones

The reactions of 4-alkyl-3-thiosemicarbazides with β-halophenones and o-halophenones gave 4,5-dihydro-N-alkyl-3-phenyl-1H-pyrazole-1-carbothioaraides and 3-phenyl-1H-indazoles, respectively.     

Determination of the configuration in six-membered saturated heterocycles (N,P, S,Se) and their oxidation products using experimental and calculated NMR chemical shifts

The six-membered saturated heterocycles—4-tert-butyl-1-methylpiperidine, 4-tert-butyl-1-methylphosphine, 4-tert-butyl-tetrahydro-2H-thiopyran, and 4-tert-butyl-tetrahydro-2H-selenopyran—were prepared as suitable model compounds with well-defined geometry for an NMR study of their oxidation products. The corresponding epimeric N-oxides, phosphinoxides, sulfoxides, and selenoxides were obtained by standard chemical preparation and also by in situ oxidation with meta-chloroperbenzoic acid directly in the NMR tube. The experimental ¹H and ¹³C chemical shifts were compared with corresponding calculated data obtained by GIAO approach with DFT, MP2, and HF methods and various basis sets. The correlation of experimental versus calculated data showed the possibility to determine the stereochemistry of the epimeric oxidation products using fast DFT B3LYP/6-31G* method for both geometry optimization and NMR chemical shifts calculation.     

AlCl3-promoted reaction of cycloalkanones with hydrazones: a convenient direct synthesis of 4,5,6,7-tetrahydro-1H-indazoles and their analogues

The AlCl₃-promoted reactions of cycloalkanones with hydrazones are described. This approach represents a mild and operationally simple method to access 2,3-diaryl-4,5,6,7-tetrahydro-1H-indazoles and their analogues in good to moderate yields.