Nickel‐Catalyzed Electrochemical Synthesis of Dihydro‐Benzo[b]thiophene Derivatives

Abstract

The intramolecular electrochemical reductive cyclization of ortho‐haloaryl allyl thioethers catalyzed by Ni(II) complexes associated to cyclam ligands affords dihydro‐benzo[b]thiophene derivatives in moderate to good yields.     

Studies in Thio‐Claisen Rearrangement: Regioselective Synthesis of Thiopyrano[2,3‐b]pyran‐2‐ones and Thieno[2,3‐b]pyran‐2‐ones

Abstract

4‐Mercapto‐6‐methyl‐2‐pyrone was alkylated with different allylic and propargylic halides under phase transfer catalyzed condition in the presence of TBAB or BTEAC catalyst in chloroform–aqueous NaOH (1%) at room temperature. The S‐alkylated thiopyran‐2‐ones were then refluxed in quinoline or in chlorobenzene to give 4‐chloromethylthiopyrano[2,3‐b]pyran‐2‐one and 4‐hydroxymethylthiopyrano[2,3‐b]pyran‐2‐one or several thieno[2,3‐b]pyran‐2‐ones.     

Synthesis of Benzo[b]benzo[2,3‐d]thiophen‐6,9‐diones via Palladium(II) Acetate–Mediated Cyclization of 5‐Arylthiocyclohexa‐2,5‐diene‐1,4‐diones

Palladium(II)‐mediated oxidative cyclization of 5‐arylthiocyclohexa‐2,5‐diene‐1,4‐diones 4 giving biologically important benzo[b]benzo[2,3‐d]thiophene‐6,9‐diones 2 has been performed with a stoichiometric amount of palladium(II) acetate in distillated acetic acid.     

Preparation and Stereochemistry of the Isopropylidene Derivatives of 1,2‐Dihydronaphtho[2,1‐b]Furan‐1,2‐Diol and 1,2,9,10‐Tetrahydronaphtho[2,1‐b:7,8‐b′] Difuran‐1,2,9,10‐Tetraol in Comparison with the Corresponding Acetyl Derivatives

Abstract

1,2‐Dihydronaphtho[2,1‐b]furan‐1,2‐diol and 1,2,9,10‐tetrahydronaphtho[2,1‐b:7,8‐b′]difuran‐1,2,9,10‐tetraol were transformed into the corresponding isopropylidene derivatives, which were studied mainly by ¹H NMR and chiral HPLC analyses in terms of a possible transformation mechanism and stereochemistry in comparison with their corresponding acetyl derivatives.     

SbCl3‐Al2O3–Catalyzed,Solvent‐Free,One‐Pot Synthesis of Benzo[b]1,4‐diazepines

This article explores the use of antimony(III) chloride adsorbed on neutral alumina as an efficient catalyst for the one‐pot synthesis of benzo[b]1,4‐diazepines (83–94%) under solvent‐free conditions. The process is easy, efficient, ecofriendly, and economical.     

A New Route of Synthesis of 5‐(N‐Phenethylamino)salicylic Acid Derivatives by Rapid and Selective Reduction of the Amide Group with NaBH4/Acetic Acid

A good yield of 5‐(N‐phenethylamino)salicylic acid derivatives was successfully obtained from the corresponding methyl 2‐acetoxy‐5‐(N‐phenethylamino)benzoate esters by rapid and selective reduction of the amide group in the acyl protected salicylic acid with NaBH₄/acetic acid in dioxane followed by hydrolysis of the ester group.     

Efficient Cyclization of 2‐Phenoxyalkanals to 2‐Alkylbenzo[b]furans

A new and efficient route to 2‐alkylbenzo[b]furans via acid‐catalyzed cyclization of 2‐phenoxyalkanals under mild conditions over amberlyst‐15 resin has been described.     

Synthesis of 2,3‐Dihydro‐4H‐furo[3,2‐c] chromen‐4‐ones and 2,3‐Dihydronaphtho[2,3‐b]furan‐4,9‐diones by the Radical Cyclizations of Hydroxyenones with Electron-Rich Alkenes using Manganese(III) Acetate

We have obtained dihydrofurans 3a–j in the radical cyclization of 4‐hydroxycoumarin 1a and 2‐hydroxy‐1,4‐naphtoquinone 1b with electron rich alkenes 2a–i by manganese(III) acetate. Methods A and B, which have different molar ratios were studied comparatively in these reactions, and we observed that method B (molar ratio 2:1:3) gave the best results. Treatment of 4‐hydroxycoumarin 1a and electron rich alkenes 2a–e gave 2,3‐dihydro‐4H‐furo[3,2‐c]chromen‐4‐ones 3a–e in 36–86% yields by the method B. Under the same conditions, the reactions of 2‐hydroxy‐1,4‐naphtaquinone 1b with conjugated alkenes 2b and 2f–i afforded 2,3‐dihydronaphtho[2,3‐b]furan‐4,9‐diones 3f–j in an excellent yields.     

Silica-Gel–Catalyzed Conversion of Stabilized Phosphorus Ylides to Benzo[e][1,3]Thiazocin Derivatives

The reaction between triphenylphosphine, dialkylacetylenedicarboxylates, and N-benzoyl thiourea derivatives leads to intermediates such as vinyltriphenylphosphonium salts, which undergo Michael addition to produce the highly functionalized phosphorus ylides containing alkyl groups in excellent yields. Using silica gel as a catalyst, the conversion of the stabilized phosphorus ylides to benzo[e][1,3]thiazocin derivatives in solvent free conditions at 90°C in fairly high yields is achieved.     

Novel and Efficient Solid‐State Synthesis of 3‐Alkyl‐6‐Aryl‐s‐triazolo[3,4‐b]‐1,3,4‐thiadiazine Derivatives

A novel and efficient solid‐state synthesis of s‐triazolo[3,4‐b]‐1,3,4‐thiadiazine derivatives has been reported. Twelve 3‐alkyl‐6‐aryl‐s‐triazolo[3,4‐b]‐1,3,4‐thiadiazine derivatives have been synthesized in excellent yields with short reaction time.     

The Reaction of 2-Ethoxy-3-Phenylbenzo[D]-1,3, 2-Oxazaphosphorin-6-One with α-Ketocarboxylic Acid Esters: Synthesis of Benzo[d]-1,3,2-Oxazaphosphepine Derivatives

Abstract

The reactions of 2-ethoxy-3-phenylbenzo[d]-1,3,2-oxazaphosphorin-6-one with R-carbonylcarboxylic acids ethyl esters (R = CF₃, Ph, and Me) lead to the formation of seven-membered heterocycles, 2-ethoxy-9-ethoxycarbonyl-2,8-dioxo-3-phenyl-9-R-benzo[d]-1,3,2-oxazaphosphepines.     

Three‐Component,One‐Pot Synthesis of Pyrazolo[3,4‐b]pyridine Derivatives in Aqueous Media

6‐Amino‐4‐aryl‐5‐cyanopyrazolo[3,4‐b]pyridines were synthesized by a three‐component reaction of aromatic aldehydes, malononitrile, and 5‐amino‐3‐methyl‐1‐phenylpyrazole using sodium 1‐dodecanesulfonic (SDS) as catalyst in aqueous media. The reaction has the advantages of good yields, less pollution, ease of separation, and environmental friendliness.     

Bromination of 5‐Methoxyindane: Synthesis of New Benzoindenone Derivatives and Ready Access to 7H‐Benzo[c]fluoren‐7‐one Skeleton

The photobromination of 5‐methoxyindane and 5‐methoxyindanone was studied at both high and low temperatures. 1,2,3‐Tribromo‐6‐methoxyindene was easily synthesized by photolytic bromination of 5‐methoxyindane at low temperature. 1,1,2,3‐Tetrabromo‐6‐methoxyindene was obtained from the photobromination of 5‐methoxyindan at 77 °C, which could then be easily converted to the 2,3‐dibromo‐6‐methoxyindene by silver‐supported hydrolysis. Photochemical bromination of 5‐methoxy‐1‐indanone with N‐bromosuccinimide (NBS) gave 3‐bromo‐6‐methoxyindene, which upon thermolysis gave a benzo[c]fluorenone derivative.     

Solvent‐Free,One‐Pot Synthesis of Pyrano[2,3‐c]pyrazole Derivatives in the Presence of KF·2H2O by Grinding

Abstract

A solvent‐free, one‐pot process for the preparation of 4H‐pyrans in the presence of KF?·?2H₂O by grinding was achieved. Its advantages are easy workup, mild reaction conditions, high yields, and environmental friendliness.     

Synthesis of [125I]‐, [2H]‐, and [3H]‐Labeled 3‐Iodothyronamine (T1AM)

3‐Iodothyronamine (T₁AM) is a novel metabolite of thyroid hormone. In HEK‐293 cells expressing an orphan G‐protein coupled receptor, the trace amine receptor, T₁AM, potently increased cAMP accumulation. In mice, T₁AM rapidly induced hypothermia and bradycardia within minutes of administration. These results suggest the existence of a new signaling pathway, the stimulation of which leads to rapid physiological and behavioral consequences. Isotope‐labeled T₁AM derivatives would be useful to study the biology and pharmacology of T₁AM. Herein we describe efficient syntheses of [¹²⁵I]‐, [²H]‐, and [³H]‐T₁AM.     

Sulfamic Acid–Catalyzed One‐Pot Synthesis of 3‐(4,6‐Dimethyl‐oxazolo[4,5‐c]quinolin‐2‐yl)‐chromen‐2‐ones using the Conventional Method and Microwave Irradiation

A rapid and efficient method for the preparation of 3‐(4,6‐dimethyl‐oxazolo[4,5‐c]quinolin‐2‐yl)‐chromen‐2‐ones by the reaction between 3‐amino‐2,8‐dimethyl‐quinolin‐4‐ol and 2‐oxo‐2H‐chromen‐3‐carboxylic acid using sulfamic acid as a acid catalyst and dimethyl formamide as a solvent using the conventional method and microwave irradiation is reported.     

Caro's Acid–Silica Gel: An Efficient and Versatile Catalyst for the One-Pot Synthesis of Tetrahydrobenzo[b]pyran Derivatives

An efficient one-pot synthesis of tetrahydrobenzo[b]pyran is described. This involved the three-component reaction of aromatic aldehydes, molononitrile, and dimedone in the presence of a catalytic amount of Caro's acid supported on silica gel in ethanol/water under reflux.     

Au(Ⅰ)-Catalyzed 6-endo-dig Cyclizations of Aromatic 1,5-Enynes to 2-(Naphthalen-2-yl)anilines Leading to Divergent Syntheses of Benzo[α]carbazole,Benzo[c,h]cinnoline and Dibenzo[i]phenanthridine Derivatives

A gold(Ⅰ)-catalyzed 6-endo-dig cyclization of aromatic 1,5-enynes was developed to synthesize 2-(naphthalen-2-yl)anilines.The functional group tolerance of this cyclization was examined systematically and a possible mechanism was proposed.The derivatization of 2-(naphthalen-2-yl)aniline was carried out to facile access to benzo[α]carbazole,benzo[c,h]cinnoline and dibenzo[i]phenanthridine derivatives in a divergent way.     

Sulfamic Acid–Catalyzed,Three-Component,One-Pot Synthesis of [1,2,4]Triazolo/Benzimidazolo Quinazolinone Derivatives

An efficient and convenient approach is reported for three-component, one-pot synthesis of the [1,2,4]triazolo/benzimidazolo quinazolinones by condensation of 2-amino benzimidazole or 3-amino-1,2,4-triazole as amine sources with dimedone and different aldehydes in the presence of sulfamic acid as a reusable, green catalyst in acetonitrile and under heating conditions.     

Simple,Mild, and Efficient Method for the Reduction of 1,4‐Benzoquinones to Hydroquinones by the Action of NaN3

A simple, mild, and efficient method is presented for the reduction of 1,4‐benzoquinones to hydroquinones by the action of NaN₃ under neutral conditions in the presence of water.