Reactions of Nucleophiles with Reactive Intermediates in the 3,4,6‐Tri‐O‐benzyl‐d‐glucal–TfOH–n‐Bu4NI Reaction System

The unique reactive intermediate formed in the 3,4,6‐tri‐O‐benzyl‐d‐glucal–TfOH (triflic acid)–n‐Bu₄NI reaction system (in dichloromethane) reacted with nucleophiles in a regio‐ and stereoselective manner. These selectivities resulted in hitherto unknown compounds, such as benzyl 4,6‐di‐O‐benzyl‐2,3‐dideoxy‐3‐iodo‐α‐glucopyranoside, which was obtained in the presence of an iodide ion as a nucleophile. The corresponding 2‐deoxy α‐glycosides were obtained exclusively in the corresponding reaction with hydroxylic nucleophiles.     

One‐Pot Synthesis of 2‐Arylthio‐2‐cyclohexenone Derivatives by the Diels–Alder Reaction of 4‐Arylthio‐3‐hydroxy‐2‐pyrones

The base‐catalyzed Diels–Alder reactions of 4‐arylthio‐3‐hydroxy‐2‐pyrones are reported. Treatment of 4‐arylthio‐3‐hydroxy‐2‐pyrones and dienophiles with triethylamine gave 2‐arylthio‐2‐cyclohexenone derivatives by the Diels–Alder reaction involving a decarboxylation in excellent to reasonable yields.     

Carbohydrate Derivative from Baylis–Hillman Adduct. An Easy and Short Synthesis of 2‐Deoxy‐2‐C‐methylene‐D‐erythro‐pentono‐1,4‐lactone

Abstract

A simple and straightforward approach for the synthesis of an α‐methylene‐δ‐butyrolactone from a Baylis–Hillman adduct obtained from a chiral α‐hydroxy aldehyde, is described.     

Aza–Baylis–Hillman Reaction of N‐Tosylated Imines with Acrylamide or N‐Arylacrylamide

Acrylamide or N‐arylacrylamide could undergo aza–Baylis–Hillman addition reaction with N‐tosylated imines with phenol as additive and DABCO as catalyst in the absence of solvent.     

Europium Triflate–Catalyzed One‐Pot Synthesis of 2,4,5‐Trisubstituted‐1H‐imidazoles via a Three‐component Condensation

A simple, efficient, and practical procedure for synthesis of 2,4,5‐trisubstituted‐1H‐imidazoles via the condensation of benzoin or acetoin, aromatic aldehydes, and ammonium acetate using europium triflate [Eu(OTf)₃] as a novel catalyst in high yields is described. The catalyst can be recovered conveniently and reused at least four times without any loss of activity.     

Novel Carbon–Carbon Bond Formation between N‐Methyl‐3‐phenyl‐3‐hydroxypropylamine and Cresols Catalyzed by p‐Toluenesulphonic Acid

The p‐toluenesulphonic acid–catalyzed reaction between appropriate cresols and N‐methyl‐3‐phenyl‐3‐hydroxypropylamine in refluxing toluene resulted in the formation of o‐substituted phenol derivatives by an aromatic nucleophilic substitution reaction.     

Cesium Carbonate–Promoted Michael‐Type Addition of Thiols to Hex‐1‐en‐3‐ulose: A Practical Synthesis of 2‐Deoxy‐1‐thio‐α‐hexopyranosid‐3‐ulose Template

The template 2‐deoxy‐1‐thio‐α‐hexopyranosid‐3‐ulose was synthesized in quantitative yield and high diastereoselectivity by 1,4‐addition of aryl and alkyl thiols to hex‐1‐en‐3‐ulose promoted by cesium carbonate in THF.     

1‐n‐Butyl‐3‐Methylimmidazolium Tetrafluoroborate–Promoted Green Synthesis of 5‐Arylidene Barbituric Acids and Thiobarbituric Acid Derivatives

The room temperature ionic liquid 1‐n‐butyl‐3‐methylimmidazolium tetrafluoroborate ([bmim]BF₄) was used to promote the synthesis of 5‐arylidene barbituric acids and thiobarbituric acid derivatives under the solid‐state conditions of grinding or microwave irradiation without organic solvent. The yields were 77.9–96.2%. It is shown that the proposed method is fast, efficient, and environmentally benign.     

Effect of Substitution in Stannic Chloride–Mediated Heterocyclization of 4‐Allyl‐3‐hydroxyquinolin‐2(1H)‐ones

Effect of substituents at the allylic position in a stannic chloride–iodine–mediated heterocyclization of 4‐allyl‐3‐hydroxyquinolin‐2(1H)‐ones for the regioselective formation of five‐ and six‐membered heterocyclic rings has been rationalized by the application of restricted Hatree–Fock calculation.     

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.     

Zinc Hydroxyapatite–Catalyzed Efficient Synthesis of 5‐Substituted 1H‐Tetrazoles

Zinc hydroxyapatite (ZnHAP) is an effective heterogeneous catalyst for the (2+3)‐cycloaddition of sodium azide with nitriles to afford 5‐substituted 1H‐tetrazoles in good yields. The catalyst is recovered and reused for several cycles with consistent activity.     

Intramolecular Cyclization of 9,11‐Seco‐Estrane under Friedel–Crafts Reaction Conditions

An intramolecular cyclization of 17β‐acetoxy‐3‐methoxy‐9,11‐seco‐1,3,5(10)‐estratriene‐11‐oic acid under different Friedel–Crafts reaction conditions is described.     

One‐Pot Synthesis of Oxime Derivatives of 1,3‐Diphenylpyrazole‐4‐carboxaldehydes from Acetophenone Phenylhydrazones Using Vilsmeier–Haack Reagent

A one‐pot synthesis of oxime derivatives 3a–3f of 1‐phenyl‐3‐arylpyrazole‐4‐carboxaldehydes has been accomplished by the Vilsmeier–Haack reaction of acetophenone phenylhydrazones 1a–1f under a new workup procedure.     

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.     

Solvent‐Free,Palladium‐Catalyzed Suzuki–Miyaura Cross‐Couplings of Aryl Chlorides with Arylboronic Acids

Pd(MeCN)₂Cl₂/PCy₃ was found to be an efficient catalytic system for the Suzuki–Miyaura cross‐couplings of aryl chlorides with arylboronic acids under solvent‐free conditions. Furthermore, the presence of the conventional solvents had deleterious effect on the reaction. In the presence of Pd(MeCN)₂Cl₂, PCy₃, and TBAF (tetra‐n‐butylammonium fluoride), a number of aryl chlorides including heteroaryl chlorides were coupled with arylboronic acids or heteroarylboronic acids smoothly to afford the corresponding products in moderate to excellent yields.     

Regioselective Synthesis of 2H‐Benzothiopyrano[3,2‐c]quinolin‐7(8H)‐ones by Tri‐n‐butyltinhydride–Mediated Radical Cyclization

A number of hitherto unreported 2H‐benzothiopyrano[3,2‐c]quinolin‐7(8H)‐ones have been regioselectively synthesized in 90–96% yield by tri‐n‐butyltinhydride–AIBN–mediated radical cyclization from 4‐(2′‐bromothioarylmethyl)‐1‐methylquinolin‐2(1H)‐ones and their corresponding sulfones. 4‐(2′‐Bromothioarylmethyl)quinolin‐2(1H)‐ones were in turn prepared from 4‐bromomethylquinolin‐2(1H)‐one and o‐bromothiophenols by refluxing in acetone in the presence of anhydrous K₂CO₃. These were converted to the corresponding sulfones by oxidation with two equivalents of m‐CPBA in refluxing dichloromethane for 1 h.     

Bismuth Trichloride–Catalyzed C‐Alkylation of Pyrroles with Electron‐Deficient Olefins

The BiCl₃‐catalyzed reaction of pyrroles with electron‐deficient olefins generated the corresponding Michael adducts in high yields.     

Improved Protocol for Thorpe Reaction: Synthesis of 4‐Amino‐1‐arylpyrazole using Solid–Liquid Phase‐Transfer Conditions

Solid–liquid phase‐transfer conditions were employed for the first time in the Thorpe reaction to synthesize 4‐amino‐1‐aryl‐3,5‐substituted‐1H‐pyrazoles 3. Aryl amines were diazotized and coupled with various active methylene compounds such as cyano acetamide, cyanoacetophenone, malononitrile, and ethyl cyanoacetate, resulting into α‐arylhydrazononitriles 1. Cyclization of 1 using α‐bromo ketones or esters resulted in compounds 3.     

Two‐Step Novel Synthesis of 2‐Amino‐6‐(1,3‐dioxo‐2,3‐dihydro‐1H‐inden‐2‐yl)‐4,7‐diphenyloxepine‐3‐carbonitrile and 5‐(1,3‐Dioxo‐2,3‐dihydro‐1H‐inden‐2‐yl)‐2‐imino‐6‐phenyl‐2H‐pyran‐3‐carbonitrile

Starting from indan‐1,3‐dione, a novel two‐step synthesis of the oxepine derivatives 5a,b and the pyran derivatives 7 and 8 under very simple reaction conditions is described.     

Synthesis of 3‐Heteroaryl‐Substituted Tetrahydrofurans from the Baylis–Hillman Adducts of Heteroarylaldehydes by n‐Bu3SnH‐Mediated 5‐exo‐trig Vinyl Radical Cyclization

The synthesis of 3‐heteroaryl‐substituted tetrahydrofurans from the propargyl derivative of Baylis–Hillman adducts of heteroaryl aldehydes by n‐Bu₃SnH‐mediated 5‐exo‐trig vinyl radical cyclization in high yield is reported.