Synthesis of N‐Protected/Free Indole‐7‐Carboxaldehyde

A direct method for the preparation of N‐protected/free indole‐7‐carboxaldehyde is reported from the corresponding N‐protected 7‐bromomethylindoles using three different conditions.     

Thermal and Microwave‐Assisted Conjugate Additions of Indole on Electron‐Deficient Nitro‐olefins

Conjugate addition of indole on nitro‐olefins was carried out by three different methods: (i) thermal heating in a sealed tube, (ii) reaction with indolyl magnesium iodide, and (iii) microwave irradiation. Comparison of the results indicated that the microwave technique is most efficient.     

N‐Alkylation of Indole Compounds in Modified Wittig–Horner Reaction

N‐Ethyl‐3‐styrylindoles are prepared under modified Wittig–Horner reaction conditions.     

PTC‐Promoted Japp–Klingmann Reaction for the Synthesis of Indole Derivatives

Abstract

Indole derivatives have been efficiently synthesized from ethyl 2‐phenylhydrazono‐5‐phthalimido‐pentanoate and its derivatives, which were obtained by Japp–Klingmann reaction under phase‐transfer catalytic (PTC) conditions. Several different phase‐transfer catalysts were investigated and dimethyldioctadecyl ammonium chloride (DMDOA) was found to promote this reaction efficiently. Using DMDOA as the PTC, aryl hydrazones were obtained in yields of 90%. The pure aryl hydrazones were then efficiently cyclized to indole derivatives in yields of more than 80%.     

Preparation of Some Derivatives of N‐tert‐Butyldecahydro‐3‐isoquinoline Carboxamide

N‐tert‐Butyldecahydro‐3‐isoquinoline carboxamide (1) is a key structural fragment present in a variety of medicinally important HIV protease inhibitors. Derivatives of this carboxamide were prepared by alkylation with either 2‐iodoethanol, allyl bromide, or bromoacetaldehyde dimethylacetal. The corresponding aldehyde of the dimethylacetal derivative was prepared by reaction with BBr₃ in CH₂Cl₂.     

Synthesis of cis‐3‐methyl‐4‐aminopiperidine Derivatives

A facile approach for the preparation of cis‐3‐methyl‐4‐aminopiperidine derivatives is described. The synthesis was carried out via regioselective ring opening of N‐benzyl‐3‐methyl‐3,4‐epoxi‐piperidine (8), which can be easily obtained in two steps from the corresponding N‐benzyl‐pyridinium salt (5). Seven new cis‐3‐methyl‐4‐amino and amido piperidines compounds were obtained.     

Regioselective Endocyclic Oxidation of Enantiopure 3‐Alkylpiperidines: Synthesis of (3S,5S)‐(‐)‐3‐Ethyl‐5‐Methylpiperidine

An efficient regioselective endocyclic oxidation of enantiopure 3‐alkylpiperidines 1(a–c) with bromine in acetic acid to generate the corresponding 5‐alkylpiperidin‐2‐ones 3(a–c) as main product is described. In addition, starting from 3a or 3b, the synthesis of (3S,5S)‐(‐)‐3‐ethyl‐5‐methylpiperidine 6 · HCl was achieved. Finally, the X‐ray single‐crystal analysis of compound 4 is reported.     

Improved Synthesis of 1‐Hydroxy‐2,2,5,5‐tetramethyl‐3‐imidazoline 3‐Oxide (HTIO)

A simple, efficient, mild, and reproducible method for the synthesis of 1‐hydroxy‐2,2,5,5‐tetramethyl‐3‐imidazoline 3‐oxide is described. The method is based on the condensation of 2‐hydroxyamino‐2‐methylpropanal oxime with 2,2‐diethoxypropane in the presence of an equimolar quantity of acetic acid. Cost‐effectiveness of the condensation procedure could be also achieved by replacing 2,2‐diethoxypropane with less expensive 2,2‐dimethoxypropane.     

Efficient Synthesis of Substituted 2‐Amino‐3‐carbethoxythiophenes

A microwave‐assisted method for the synthesis of a variety of thiophene o‐aminoesters (2a–l) has been developed, starting from an appropriate aldehyde, methyl ketone or acetoacetate ester with ethyl cyanoacetate in the presence of elemental sulfur.     

Catalytic Oxidative Cyclocondensation of o‐Aminophenols to 2‐Amino‐3H‐phenoxazin‐3‐ones

The catalytic oxidative cyclocondensation of the o‐aminophenols 1a–f was investigated. The oxidants used were air/laccase, H₂O₂/horseradish peroxidase, H₂O₂/ebselen (3), and TBHP/diphenyl diselenide 4. The products obtained were 2‐amino‐3H‐phenoxazin‐3‐one—questiomycin A, its derivative 2b, and cinnabarinic acid and actinocin (2c,d). Substrates with methyl groups at 4 and 5 positions of benzene ring were converted to different dihydrophenoxazinones 2g,h. Compounds having chlorine atoms at the same positions underwent oxidation to planar phenoxa-zinones 2e,f with elimination of one hydrochloride molecule.     

Solid‐State Synthesis of 4‐[(Indol‐3‐yl)‐arylmethyl]‐1‐phenyl‐3‐methyl‐5‐pyrazolones by Catalysis of Molecular Iodine

4‐[(Indol‐3‐yl)‐arylmethyl]‐1‐phenyl‐3‐methyl‐5‐pyrazolones could be smoothly and effectively obtained in good yields through the iodine‐catalyzed reactions under solid‐state conditions at room tempertaure. The three‐component approach in a one‐pot procedure was reported for the first time. A possible mechanism was suggested to elucidate the remarkable reaction selectivities.     

Structure of 2,4,4,5,5‐pentamethyl‐2‐imidazoline‐1‐oxyl‐3‐oxide

The crystal and molecular structures of the stable nitroxide radical 2,4,4,5,5pentamethyl2imidazoline1oxyl3oxide was determined. The N—O bond lengths are 1.279(2) and 1.280(2), respectively. The O^-—N⁺=C—N— O fragment is nearly planar with carbon atoms of the ethyl fragment that deviated from the O—N⁺=C—N—O plane by –0.204(5) and +0.176(5). The minimum intermolecular distance between the oxygen atoms of NO groups is 4.094.     

Synthesis and Crystal Structure of 3-（Trichloroacetyl） Indole

1 INTRODUCTION Indole and its derivatives have attracted much at-tention due to their chemical properties as well asbiological activities[1, . They have been widely used 2]as the materials for producing pigment, perfume,plant growth regulators, etc. Recently, it has alsobeen found that some indole derivatives present anti-tumor and antiviral activities[3～5]. During our sear-ches for bioactive compounds, a series of indole deri-vatives were synthesized, among …     

Simple and Convenient Synthesis of 4‐Unsubstituted‐3‐(3‐Oxoalkyl)isocoumarins

A simple transformation of 2‐alkylfurans and 2‐formylbenzoic acids into 4‐unsubstituted 3‐(3‐oxoalkyl)isocoumarins is described. It is based on the synthesis of 2‐(2‐carboxybenzyl)furans followed by their acid‐catalyzed recyclization to the target isocoumarins.     

Practical Synthesis of 3‐Carboxyindazoles

A clean, high‐yielding synthetic route to methyl 5‐(bromomethyl)‐1‐tritylindazole 3‐carboxylate 1 was needed. A principal intermediate was 5‐methyl‐3‐carboxyindazole 2. An analysis of a by‐product found after executing Schad's 3‐carboxyindazole synthesis led to undertaking this reaction with an inverse addition in the principal step. This simple modification gave 2 in excellent and reproducible yields.     

Heterocyclization of Imidates with 3‐Alkyl‐5‐amino‐1‐phenyl‐1,2,4‐triazoles: Synthesis of New Triazolotriazines

Some novel triazolo[4,3‐a]triazines derivatives were synthesized by reaction of N‐cyanoimidates and N‐ethoxycarbonylimidates with 3‐alkyl‐5‐amino‐1‐phenyl‐1,2,4‐triazoles.     

Efficient and Simple Synthesis of Substituted 3‐Phenyl‐7‐methoxybenzopyrans as Pseudo‐Vitamin‐D3 Analogs

An efficient and simple synthesis of substituted 3‐phenyl‐7‐methoxybenzopyrans as pseudo‐vitamin‐D₃ analogs in good yields under mild reaction conditions is described.     

Synthesis of O‐β‐D‐Glucopyranosides of 7‐Hydroxy‐3‐(imidazol‐2‐yl)‐4H‐chromen‐4‐ones

The 7‐hydroxy‐3‐formyl‐4H‐chromen‐4‐one 1 reacted with various cyclic 1,2‐dicarbonyl compounds in the presence of ammonium acetate to furnish 7‐hydroxy‐3‐([4,5‐fused] imidazol‐2‐yl)‐4H‐chromen‐4‐ones 2a–f, which on glucosylation with α‐acetobromoglucose affords 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyloxy‐3‐([4,5‐fused] imidazol‐2‐yl)‐4H‐chromen‐4‐ones 3a–f. 7‐O‐β‐D‐Glucopyranosyloxy‐3‐([4,5‐fused] imidazol‐2‐yl)‐4H‐chromen‐4‐ones 4a–f were prepared by deacetylation with anhydrous zinc acetate in absolute methanol. The structure of these new O‐β‐D‐glucosides was established on the basis of chemical, elemental, and spectral analysis. These compounds were evaluated for their in vitro biological activity.

     

Microwave‐Assisted Synthesis of cAMP Phosphodiesterase Inhibitor 8‐Hydroxy‐6,7‐dimethoxy‐3‐hydroxymethylisocoumarin

An efficient microwave‐assisted synthesis of 8‐hydroxy‐6,7‐dimethoxy‐3‐hydroxymethyl isocoumarin (1), a metabolite of Streptomyces mobaraensis and structural relative of reticulol and cytogenin that possesses potent cyclic nucleotide phosphodiesterase inhibitor activity, is described. 3,4,5‐Trimethoxyhomophthalic acid (2) was condensed with acetoxyacetyl chloride under microwave irradiation and the acid hydrolysis of resulting 6,7,8‐trimethoxy‐3‐acetoxymethylisocoumarin (3) afforded the 6,7,8‐trimethoxy‐3‐hydroxymethylisocoumarin (4). Regioselective demethylation of the latter using magnesium iodide in THF yielded the title compound (1).     

Reaction of Imines with 5,5‐Dimethyl‐1, 3‐cyclohexandione

The reaction of imines 1 with 5,5‐dimethyl‐1,3‐cyclohexandione 2 in methanol was investigated. When the reaction was carried out without a catalytic amount of molecular iodine, ring‐opening derivatives of xanthenediones 3 were obtained in high yields. On the other hand, when molecular iodine and a catalytic amount of zinc powder were employed as the catalyst, xanthenediones derivatives 4 were obtained with excellent yields.