Synthesis of New Bis‐1,2,4‐Oxadiazoline Derivatives via 1,3‐Dipolar Cycloaddition Reaction

A series of novel bis‐oxadiazoline derivatives 4 was synthesized via 1,3‐dipolar cycloaddition reaction of bis‐aldimines 3 , and nitrile oxides generated in situ from various benzohydroximinoyl chlorides in the presence of Et₃N. The target products were confirmed by IR, ¹H‐NMR, and mass spectrometry.     

Synthesis of 1,5‐Benzodiazepine Derivatives Containing 1,2,3‐Triazole Moiety via 1,3‐Dipolar Cycloaddition Reaction

A series of 1,5‐benzodiazepine derivatives were synthesized by the reaction of 1,5‐benzodiazepine containing 1,2,3‐triazole moiety with benzohydroximinoyl chlorides at room temperature. The structural identities of these novel compounds were confirmed on the basis of IR, ¹H NMR, mass spectral and elemental analysis data, and by X‐ray crystallographic analysis of a typical example of the new class of 1,5‐benzodiazepine analogs.     

Synthesis of New Spirooxindole‐Fused Isoxazoline/Triazole and Isoxazoline/Isoxazole Derivatives from Three‐Component 1,3‐Dipolar Cycloaddition

A series of diverse heterocycles containing spirooxindole, isoxazoline/triazole, and isoxazole rings has been synthesized via an efficient three‐component reaction of (E )‐2‐(1‐propargyl‐2‐oxoindoline‐3‐ylidene)acetophenones 1 , arylnitrile oxides 2 , and arylazides 3 using Cu(I) as catalyst. The regiochemistry and stereochemistry of cycloadducts 4a and 5a have been confirmed by X‐ray diffraction studies. The heterocycles were screened against Gram‐positive and Gram‐negative bacteria and fungi. Several compounds exhibit moderate to excellent activities comparable to those of established standard drugs.     

Design and Synthesis of Novel Quinoline Tethered Tricyclic 1,5‐Benzothiazepine Derivatives via 1,3‐Dipolar Cycloaddition Reaction

A series of novel substituted‐[1,2,4]oxadiazolo[5,4‐d][1,5]benzothiazepine derivatives contain quinoline ring 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l were synthesized by the reaction of benzothiazepines 4a , 4b , 4c and substituted‐benzohydroximinoyl chlorides through the 1,3‐dipolar cycloaddition reaction in the presence of Et₃N at room temperature. The structures of the obtained adducts were elucidated by MS, IR, ¹H NMR, and elemental analyses. In addition, the structures of 5e were further confirmed by X‐ray single crystal diffraction study.     

Synthesis of Novel Spiro Thiazolotriazole Derivatives via 1,3‐Dipolar Cycloaddition of Azomethine Ylide

The 1,3‐dipolar cycloaddition of azomethine ylide generated in situ from isatin and sarcosine to 5‐arylmethylidene thiazolo[3,2‐b][1,2,4]triazol‐6(5H)‐ones afforded novel 1′‐methyl‐4′‐aryldispiro[indole‐3,2′‐pyrrolidine‐3′,5″‐[1,3]thiazolo[3,2‐b][1,2,4]triazole]‐2,6″ (1H)‐diones in moderate yields. The structures of all the products were characterized thoroughly by NMR, infrared spectroscopy (IR), mass spectroscopy (MS) elemental analysis together with X‐ray crystallographic analysis.     

An Efficient Three‐Component Synthesis of Pyranoquinoline Derivatives

Pyranoquinoline derivatives have been synthesized via three‐component reaction of 4‐hydroxy‐1‐methyl‐2(1H)‐quinolinone and dialkyl acetylenedicarboxylates in the presence of nucleophiles such as alkyl isocyanides and triphenylphosphine.     

Synthesis of Spiro Pyrrolobenzothiazole Derivatives via a Three‐Component Reaction

A novel three‐component reaction involving 2‐methylbenzothiazole or 2,5‐dimethylbenzothiazole, acetylenic esters and 1,3‐dicarbonyl compounds such as (1,3‐dimethylbarbituric acid or 1,3‐indanedione) leading to the synthesis of spiro pyrrolobenzothiazole derivatives. The reactions proceeded smoothly at room temperature without using any catalyst. This method is very useful to functionalize benzothiazole derivatives in a one‐pot operation. The structures of the synthesized compounds have been characterized by spectral studies.     

Expedient Synthesis of Novel Ferrocenyl Spiropyrrolidines Through 1,3‐Dipolar Cycloaddition Reaction

The synthesis of novel ferrocenyl spiropyrrolidines through the cycloaddition of azomethine ylides generated by a decarboxylative route from sarcosine and diketones with the dipolarophile, Knoevenagel adduct of ferrocene carbaldehyde is described. The regiochemistry and stereochemistry of the cycloadducts were confirmed by X‐ray analysis of one of the synthesized cycloadducts.     

Synthesis of Spirocyclic and Tricyclic Isoxazoline via 1,3‐Dipolar Cycloaddition Reactions

1,3‐Dipolar cycloadditions of the bicyclic monoterpenes (S)‐(?)‐camphene ( 1 ), (R)‐(+)‐a‐pinene ( 2 ), and (S)‐(?)‐b‐pinene ( 3 ) with aryl and heteroaryl nitrile oxides afforded new spirocyclic and tricyclic isoxazoline derivatives 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 whose biological activities were evaluated in bioassay studies.     

Synthesis of Novel 1,2,4‐oxadiazoline Derivatives Containing Quinoline Moiety by 1,3‐Dipolar Cycloaddition

A series of novel 1,2,4‐oxadiazoline derivatives containing 2‐(1,2,4‐triazol‐1‐yl)quinoline were synthesized by the reaction of imines with benzohydroximinoyl chlorides in the presence of Et₃N via 1,3‐diplolar cycloaddition reaction. The structures of the target compounds were confirmed by IR, ¹H NMR, MS, elemental, and X‐ray crystallographic analysis.     

Synthesis of 2‐Oxopyridine‐Fused 1,3‐Diazaheterocyclic Compounds via a Three‐Component Reaction

An efficient and simple route for the preparation of 2‐oxopyridine‐fused 1,3‐diazaheterocyclic compounds via a three component reaction is described. It involves the reaction between alkylenediamines 1 , 1,1‐bis(methylsulfanyl)‐2‐nitroethene, and alkyl prop‐2‐ynoates 2 in refluxing THF (Table). The structures were corroborated by spectroscopic (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and elemental analyses. A plausible mechanism for this type of cyclization is proposed (Scheme).     

A Novel Coupling 1,3‐Dipolar Cycloaddition Sequence as a Three‐Component Approach to Highly Fluorescent Indolizines

Indolizines 4 and biindolizines 6 can be synthesized in moderate yields in a consecutive one‐pot three‐component process by a coupling/1,3‐dipolar cycloaddition sequence of a (hetero)arenecarbonyl chloride 1 , a terminal alkyne 2 , and a suitable 1‐(2‐oxoethyl) pyridinium bromide 3 or 5 , respectively (Schemes 1 and 2). After the Sonogashira coupling, a [2+3] cycloaddition of the in situ formed pyridinium ylide, an allyl‐type 1,3‐dipole, furnishes a cycloadduct that is instantaneously oxidatively aromatized to give the highly fluorescent indolizine derivatives that were unambiguously characterized by an X‐ray‐structure analysis of compound 4d (Fig. 1). Additionally, fluorescence studies with pyridinyl‐substituted representatives reveal not only that indolizines and biindolizines are highly interesting fluorescence dyes but that their fluorescence color can also be reversibly switched upon altering the pH of the medium.     

Unexpected 1,3‐Dipolar Cycloaddition Reaction of Thiazolo[3,2‐a]pyrimidine Derivatives and Nitrilimine

The 1,3‐dipolar cycloaddition reactions of nitrilimine with thiazolo[3,2‐a]pyrimidine derivatives was investigated. Bis‐cycloadducts were obtained through a domino 1,3‐dipolar cycloaddition/ring‐opening/ring‐opening/1,3‐dipolar cycloaddition processes. The structures of the products were characterized thoroughly by NMR, IR, MS, elemental analysis together with X‐ray crystallographic analysis.     

Facile Method for 1,3‐Dipolar Cycloaddition Reaction of Azomethine Ylides: Highly Stereoselective Synthesis of Substituted Pyrrolidine Derivatives

The substituted pyrolidine derivatives with high stereoselectivity were obtained through cycloaddition reaction in the presence of a Lewis acid namely diethylzinc by solvent‐free grinding method.     

The Huisgen Reaction: Milestones of the 1,3‐Dipolar Cycloaddition

The concept of 1,3‐dipolar cycloadditions was presented by Rolf Huisgen 60 years ago. Previously unknown reactive intermediates, for example azomethine ylides, were introduced to organic chemistry and the (3+2) cycloadditions of 1,3‐dipoles to multiple‐bond systems (Huisgen reaction) developed into one of the most versatile synthetic methods in heterocyclic chemistry. In this Review, we present the history of this research area, highlight important older reports, and describe the evolution and further development of the concept. The most important mechanistic and synthetic results are discussed. Quantum‐mechanical calculations support the concerted mechanism always favored by R. Huisgen; however, in extreme cases intermediates may be involved. The impact of 1,3‐dipolar cycloadditions on the click chemistry concept of K. B. Sharpless will also be discussed.     

Synthesis and Characterization of Novel 1,2,4‐oxadiazoline Derivatives Containing Pyrazole Moiety by 1,3‐Dipolar Cycloaddition

A series of novel pyrazolyl‐oxadiazoline derivatives bearing 1,2,4‐triazole moiety 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l , 4m , 4n , 4o , 4p were synthesized by schiff bases of 3‐methyl‐1‐phenyl?5‐(1,2,4‐triazole‐1‐yl)‐4‐formylpyrazole 3a , 3b , 3c , 3d and various benzohydroximinoyl chlorides in the presence of Et₃N via 1,3‐dipolar cycloaddition reaction. The target products were confirmed by IR, ¹H‐NMR, MS, elemental analysis. In addition, the structure of compound 4d was defined by X‐ray crystallography.     

An Efficient One‐Pot Three‐Component Synthesis of Some New Polyhydroquinolines via Enaminone Intermediates

For a wide spectrum of pharmacological effects of polyhydroquinolines, this study introduces a developed safe, simple, higher yields and fast method for the synthesis of some new hexahydroquinoline derivatives using one‐pot three‐component cyclocondensation reaction, via the reaction of 1,3‐cyclohexanedione with primary amine and arylidinemalononitrile or salicylaldehyde derivatives. The prepared compounds were reacted with different reagents as N ,N‐dimethylformamide dimethylacetal, acetic anhydride, sulphuric acid, and hydrazine hydrate forming several polycyclic hexahydroquinoline and acridine derivatives. All these new compounds have been characterized by spectral data and expected to be effective pharmaceutical drugs.