Formation of 2,6-dioxabicyclo[3.3.0]-octa-3,7-dienes or multiply substituted o-benzoquinones from reactions of 1,4-dilithio-1,3-dienes with dimethyl oxalate

Reactions of 1,4-dilithio-1,3-dienes with dimethyl oxalates afforded multiply substituted o-benzoquinones or stereodefined 2,6-dioxabicyclo[3.3.0]-octa-3,7-dienes in good yields.     

FeCl3-SiO2 as a reusable heterogeneous catalyst for the synthesis of 5-substituted 1H-tetrazoles via [2+3] cycloaddition of nitriles and sodium azide

An efficient method for the preparation of 5-substituted 1H-tetrazole derivatives is reported using FeCl₃-SiO₂ as an effective heterogeneous catalyst. This method has the advantages of high yields, simple methodology, and easy work-up. The catalyst can be recovered by simple filtration and reused delivering good yields.     

Recyclable gallium(III) triflate-catalyzed [4+3] cycloaddition for synthesis of 2,4-disubstituted-3H-benzo[b][1,4]diazepines

Simple and efficient Ga(OTf)₃-catalyzed [4+3] cycloaddition of 1,3-diarylpropynones and o-phenylenediamines is developed for the preparation of 2,4-disubstituted-3H-benzo[b][1,4]diazepines. The reaction has advantages of using a green solvent, generating a minimal amount of waste, and easy catalyst recycle.     

An expedient synthesis of indolo[1,2-a]quinolines via Mn(OAc)3-mediated oxidative free radical cyclization and NaI/O2-assisted dealkoxycarbonylation/aerobic oxidation cascade

An expedient synthetic procedure of indolo[1,2-a]quinolines was developed using a sequential Cu-mediated N-arylation of indole, Mn(OAc)₃-mediated oxidative free radical cyclization, and NaI/O₂-assisted concomitant dealkoxycarbonylation/aerobic oxidation. The last step was replaced by a palladium-catalyzed decarboxylation/elimination protocol for the allyl ester derivatives.     

An efficient synthesis of 5-substituted 1H-tetrazoles via B(C6F5)3 catalyzed [3+2] cycloaddition of nitriles and sodium azide

A simple and efficient protocol is developed for the synthesis of 5-substituted 1H-tetrazole derivatives from various nitriles and sodium azide (NaN₃) via [3+2] cycloaddition reaction using B(C₆F₅)₃ as a catalyst. The present synthetic method displayed significant advantages such as low catalyst loading, mild reaction conditions, low toxicity, easy work-up, high yields, and compatibility with other functional groups.     

Convenient oxidation of alkylated phenols and methoxytoluenes to antifungal 1,4-benzoquinones with hydrogen peroxide (H2O2)/methyltrioxorhenium (CH3ReO3) catalytic system in neutral ionic liquid

Alkylated phenol and methoxytoluene derivatives were catalytically and selectively oxidized to the corresponding 1,4-benzoquinones in good conversions and yields. Reactions were performed with hydrogen peroxide (H₂O₂)/methyltrioxorhenium (CH₃ReO₃) in 1-butyl-3-methylimidazolium tetrafluoroborate [bmim]BF₄, a neutral ionic liquid. Compounds were tested in vitro for their antifungal activity against the growth of several widespread soil fungi. Some of them were proved to be potent inhibitors of Fusarium sp. than ketoconazole, a commercially available and expensive antifungal agent.     

An efficient route to disymmetrically substituted calix[6]arenes. Synthesis of novel ligands presenting a N2S or N3CO2 binding core

The C_3v tris-methoxy calix[6]arene was selectively mono-alkylated by dibromoethane yielding a key intermediate for the design of disymmetrically O-substituted calix[6]arenes. Indeed, subsequent reactions with various functional groups afforded novel calix[6]arene-based biomimetic ligands that present a mixed donor N₂S or N₃CO₂⁻ environment in an efficient way.     

Yb(OTf)3: an efficient catalyst for the synthesis of 3-arylbenzo [f]quinoline-1,2-dicarboxylate derivatives via imino-Diels-Alder reaction

A mild and facile method for the synthesis of 3-arylbenzo[f]quinoline-1,2-dicarboxylate derivatives is reported by an imino-Diels-Alder reaction in high yields (76-92%). This procedure includes a novel three-component reaction of aromatic aldehyde, naphthalen-2-amine, and but-2-ynedioate catalyzed by Yb(OTf)₃ in toluene. The results are obviously different from those of the simple substituted aniline-involved reactions catalyzed by ZnCl₂ or KOH in the literature.     

AlCl3-mediated tandem Friedel-Crafts reactions of vinylidenecyclopropanes with acyl chlorides: a facile synthetic method for the construction of 1-[2-(2,2-diarylvinyl)-1-phenyl-3H-inden-5-yl]ethanone derivatives

AlCl₃-mediated tandem Friedel-Crafts reaction of vinylidenecyclopropanes with acyl chlorides produced the corresponding 1-[2-(2,2-diarylvinyl)-1-phenyl-3H-inden-5-yl]ethanone derivatives in moderate to good yields under mild conditions within short reaction time.     

Chiral 2-C-methylene glycosides and carbohydrate-derived pyrano[2,3-b][1]benzopyrans: synthesis via InCl3 catalyzed stereoselective Ferrier rearrangement of 2-C-acetoxymethyl glycal derivatives

2-C-Acetoxymethyl glycal derivatives react with aliphatic alcohols in the presence of InCl₃ (30 mol %) to furnish the corresponding 2-C-methylene glycosides in excellent yields and with exclusive α-selectivity except for the methyl 2-C-methylene glycosides, which are formed in ∼2:1 anomeric ratio in favour of the α-anomer. The reaction of 2-C-acetoxyglycals with phenols, however, produces the corresponding chiral carbohydrate-derived pyranobenzopyran derivatives via initial Ferrier rearrangement followed by tandem cyclization in excellent yields and moderate to high stereoselectivities in favour of the corresponding 10a-R-pyrano[2,3-b][1]benzopyran derivatives.     

Synthesis of imidazolidin-4-one and 1H-imidazo[2,1-a]isoindole-2,5(3H,9bH)-dione derivatives of primaquine: scope and limitations

The synthesis of imidazolidin-4-one derivatives of primaquine as potential antimalarial agents is described. The target compounds were synthesized in three steps: (i) condensation of (±)-primaquine with N^α-protected amino acids, (ii) removal of the N^α-protecting group, and (iii) reaction of the N-acylprimaquine with a carbonyl compound: acetone, three cyclic ketones and veratraldehyde. Using 2-formylbenzoic acid in the third step afforded 1H-imidazo[2,1-a]isoindole-2,5(3H,9bH)-diones. All products were isolated in good to excellent yields. Whereas imidazolidin-4-ones were formed as mixtures of all possible diastereomers in equal amounts, 1H-imidazo[2,1-a]isoindole-2,5(3H,9bH)-diones were produced in a stereoselective fashion. The compounds hydrolyse very slowly (t_1/2 5-30 d) in pH 7.4 buffer to release primaquine. These primaquine derivatives are being submitted to biological assays, and preliminary results of their antimalarial activity are quite encouraging.     

The design and synthesis of novel 3-[2-indol-1-yl-ethyl]-1H-indole derivatives as selective inhibitors of CDK4

We present the design, synthesis and biological activity of novel 3-[2-indol-1-yl-ethyl]-1H-indole selective inhibitors of CDK4.     

Synthesis of 1H-pyrrolo[3,2-c]quinoline derivatives via palladium-catalyzed heteroannulation of 2-aryl-3-iodo-4-(phenylamino)quinolines and 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinolines

Palladium(0)/copper iodide catalyzed Sonogashira cross-coupling of 2-aryl-3-iodo-4-(phenylamino)quinolines with terminal alkynes afforded series of 1,2,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines in a single-step operation. Conversely, the 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives were found to undergo PdCl₂(PPh₃)₂/CuI catalyzed intramolecular Heck reaction to yield the corresponding 1,3,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines.     

Domino reactions in water for the stereoselective synthesis of novel spiro dihydro-2′H-[indene-2,3′-thiophen]-1(3H)-ones with three contiguous stereocenters

The domino reactions of (E)-2-(aryl)-2,3-dihydro-1H-inden-1-ones and 1,4-dithiane-2,5-diol in the presence of triethylamine in water stereoselectively afforded a library of 2′-(aryl)-4′-hydroxy-4′,5′-dihydro-2′H-spiro[indene-2,3′-thiophen]-1(3H)-ones. This transformation presumably proceeds via the generation of 2-mercaptoacetaldehyde from 1,4-dithiane-2,5-diol followed by Michael addition–intramolecular aldol sequence with C–C and C–S bond formations and creation of three contiguous stereocenters in a one-pot operation.