Facile Synthesis of N‐(Benzyl‐1H‐1,2,3‐Triazol‐5‐yl) Methyl)‐4‐(6‐Methoxybenzo [d] Thiazol‐2‐yl)‐2‐Nitrobenzamides via Click Chemistry

A series of novel N‐((l‐benzyl‐lH‐l,2,3‐triazol‐5‐yl) methyl)‐4‐(6‐methoxy benzo[d ]thiazol‐2‐yl)‐2‐nitrobenzamide derivatives were prepared from 4‐(6‐methoxybenzo[d ]thiazol‐2‐yl)‐2‐nitro‐N‐(prop‐2‐ynyl) benzamide with benzyl azides by using click reaction (copper‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction) in the presence of CuSO₄.5H₂O and sodium ascaorbate. All the newly synthesized compounds were evaluated further in vitro antimicrobial activity against Gram‐positive bacteria (Staphylococcus aureus and Bacillus subtillis ), Gram‐negative bacteria (Echerichia coli and Pseudomonas aeuroginosa ), and fungi (Aspergillus niger and Aspergillusfumigatus ) strains. The new compounds were characterized based on spectroscopic evidence. Among them compounds 10a , 10h , and 10i were showed promising activity when compared with standard drugs Ciprofloxacin and Miconazole.     

5‐(1,2,3‐Triazol‐1‐yl)tetrazole Derivatives of an Azidotetrazole via Click Chemistry

N? C bonded (non‐bridged) 5‐(1,2,3‐triazol‐1‐yl)tetrazoles were synthesized by the Cu^I‐catalyzed 1,3‐dipolar azide–alkyne cycloaddition click reaction using 5‐azido‐N‐(propan‐2‐ylidene)‐1H‐tetrazole ( 1 ). For example, the click reaction of 1 in the presence of CuSO₄?5 H₂O and Na ascorbate at 65–70 °C for 48 h in CH₃CN/H₂O co‐solvent was found to be limited to only terminal alkynes that have electron‐withdrawing groups, CF₃C?CH ( 2 a ) and SF₅C?CH ( 2 b ), giving rise to isopropylidene‐[5‐(4‐trifluoromethyl‐1,2,3‐triazol‐1‐yl)tetrazol‐1‐yl]amine ( 3 a ) and isopropylidene‐[5‐(4‐pentafluorosulfanyl‐1,2,3‐triazol‐1‐yl)tetrazol‐1‐yl]amine ( 3 b ) in 47 % and 66 % yields, respectively. When carried out under conditions using CuI and 2,6‐lutidine as catalysts at 0 °C for 13 h in CHCl₃, the click reaction was versatile toward alkynes even those having electron‐donating groups. Properties of new products were determined and compared with those of 1 . Heats of formation, detonation pressures, detonation velocities and impact sensitivities are reported for these new 5‐(1,2,3‐triazol‐1‐yl)tetrazoles.     

A Novel ‘Domino‐Click Approach’ to Unsymmetrical Bis‐1H‐1,2,3‐triazoles

Aryl azides 1 were treated with allenylmagnesium bromide ( 2 ) to generate 1,5‐disubstituted butynyl‐1H‐1,2,3‐triazoles 3 in a domino fashion, which upon Cu^I‐catalyzed 1,3‐dipolar cycloaddition with aryl azides 4 afforded novel bis‐1H‐1,2,3‐triazoles 5 in quantitative yields (Scheme 1 and Table).     

1,3‐Dipolar Cycloaddition Reactions of Organic Azides with Morpholinobuta‐1,3‐dienes and with an α‐Ethynyl‐enamine

The cycloaddition of organic azides with some conjugated enamines of the 2‐amino‐1,3‐diene, 1‐amino‐1,3‐diene, and 2‐aminobut‐1‐en‐3‐yne type is investigated. The 2‐morpholinobuta‐1,3‐diene 1 undergoes regioselective [3+2] cycloaddition with several electrophilic azides RN₃ 2 ( a , R=4‐nitrophenyl; b , R=ethoxycarbonyl; c , R=tosyl; d , R=phenyl) to form 5‐alkenyl‐4,5‐dihydro‐5‐morpholino‐1H‐1,2,3‐triazoles 3 which are transformed into 1,5‐disubstituted 1H‐triazoles 4a , d or α,β‐unsaturated carboximidamide 5 (Scheme 1). The cycloaddition reaction of 4‐[(1E,3Z)‐3‐morpholino‐4‐phenylbuta‐1,3‐dienyl]morpholine ( 7 ) with azide 2a occurs at the less‐substituted enamine function and yields the 4‐(1‐morpholino‐2‐phenylethenyl)‐1H‐1,2,3‐triazole 8 (Scheme 2). The 1,3‐dipolar cycloaddition reaction of azides 2a – d with 4‐(1‐methylene‐3‐phenylprop‐2‐ynyl)morpholine ( 9 ) is accelerated at high pressure (ca. 7–10 kbar) and gives 1,5‐disubstituted dihydro‐1H‐triazoles 10a , b and 1‐phenyl‐5‐(phenylethynyl)‐1H‐1,2,3‐triazole ( 11d ) in significantly improved yields (Schemes 3 and 4). The formation of 11d is also facilitated in the presence of an equimolar quantity of tBuOH. The three‐component reaction between enamine 9 , phenyl azide, and phenol affords the 5‐(2‐phenoxy‐2‐phenylethenyl)‐1H‐1,2,3‐triazole 14d .     

Highly Efficient [3 + 2] Cycloaddition: Click Synthesis of Novel 1H‐indol‐3‐yl‐benzo[d]imidazole Bis‐triazoles

A series of novel 1‐((1H‐1,2,3‐triazol‐4‐yl)methyl)‐2‐(1‐((1H‐1,2,3‐triazol‐4‐yl)methyl)‐5‐substituted‐1H‐indol‐3‐yl)‐6‐substituted‐1H‐benzo[d]imidazoles 5a – i have been prepared using click chemistry as an ideal strategy where [3 + 2] cycloaddition of azides with terminal alkynes has been developed as the target compounds. In route‐II, 5‐substituted‐1H‐indole‐3‐carbaldehydes 1a – c react with 5‐substituted orthophenylenediamine 8 to give desired products, that is, 6‐substituted‐2‐(5‐substituted‐1H‐indol‐3‐yl)‐1H‐benzo[d]imidazole 6a – i . Here, 6a – i react with 2 equiv of propargylbromide 7 to give novel 6‐substituted 2‐(5‐substituted‐1‐(prop‐2‐yn‐1‐yl)‐1H‐indol‐3‐yl)‐1‐(prop‐2‐yn‐1‐yl)‐1H‐benzo[d]imidazole 4a – i . 4a – i were reacted with 2 equiv of NaN₃ in t‐butanol/water (1:2) and add catalytic amount of CuSO₄.5H₂O. Stir the reaction mixture at room temperature to get the target products 5a – i . Here, obtained products contain four rings, that is, one indole, two triazoles, and one benzimidazole. The main advantages of this method are short reaction times, easy workup, higher yields (88–92%), and no by‐products formation.     

Synthesis of 5H‐1,2,3‐triazolo[4,3‐a][2]benzazepines from the baylis‐hillman adducts of 2‐alkynylbenzaldehydes

The facile synthesis of 5H‐1,2,3‐triazolo[4,3‐a][2]benzazepines 5a‐d by the intramolecular 1,3‐dipolar cycloaddition reaction of 2‐alkynylphenylallyl azides 4a‐d is described. The latter were readily obtained from 2‐alkynylbenzaldehydes 1a‐d through the Baylis‐Hillman adducts 2a‐d followed by acetylation to compounds 3a‐d and nucleophilic substitution by azide to compounds 4a‐d.     

2‐Azido‐2‐deoxycellulose: Synthesis and 1,3‐Dipolar Cycloaddition

Chitosan ( 1 ) was prepared by basic hydrolysis of chitin of an average molecular weight of 70000 Da, ¹H‐NMR spectra indicating almost complete deacetylation. N‐Phthaloylation of 1 yielded the known N‐phthaloylchitosan ( 2 ), which was tritylated to provide 3a and methoxytritylated to 3b . Dephthaloylation of 3a with NH₂NH₂?H₂O gave the 6‐O‐tritylated chitosan 4a . Similarly, 3b gave the 6‐O‐methoxytritylated 4b . CuSO₄‐Catalyzed diazo transfer to 4a yielded 95% of the azide 5a , and uncatalyzed diazo transfer to 4b gave 82% of azide 5b . Further treatment of 5a with CuSO₄ produced 2‐azido‐2‐deoxycellulose ( 7 ). Demethoxytritylation of 5b in HCOOH gave 2‐azido‐2‐deoxy‐3,6‐di‐O‐formylcellulose ( 6 ), which was deformylated to 7 . The 1,3‐dipolar cycloaddition of 7 to a range of phenyl‐, (phenyl)alkyl‐, and alkyl‐monosubstituted alkynes in DMSO in the presence of CuI gave the 1,2,3‐triazoles 8 – 15 in high yields.     

An Efficient Synthesis of 3‐(1H‐Tetrazol‐5‐yl)coumarins (=3‐(1H‐Tetrazol‐5‐yl)‐2H‐1‐benzopyran‐2‐ones) via Domino Knoevenagel Condensation,Pinner Reaction,and 1,3‐Dipolar Cycloaddition in Water

A novel straightforward synthesis of 3‐(1H‐tetrazol‐5‐yl)coumarins (=3‐(1H‐tetrazol‐5‐yl)‐2H‐1‐benzopyran‐2‐ones) 6 via domino Knoevenagel condensation, Pinner reaction, and 1,3‐dipolar cycloaddition of substituted salicylaldehydes (=2‐hydroxybenzaldehydes), malononitrile (propanedinitrile), and sodium azide in H₂O is reported (Scheme 1 and Table 2). This general protocol provides a wide variety of 3‐(1H‐tetrazol‐5‐yl)coumarins in good yields under mild reaction conditions.     

Synthesis of New 1,2,3‐Triazole Derivatives Possessing 4H‐Pyran‐4‐one Moiety by 1,3‐Dipolar Cycloaddition Reaction of Azidomethyl Phenylpyrone with Various Alkynes

A series of new 1,2,3‐triazole derivatives were synthesized by 1,3‐dipolar cycloaddition reaction of 2‐(4‐azidomethylphenyl)‐6‐phenyl‐4H‐pyran‐4‐one with different alkynes in 40–71% yields. In the case of terminal alkynes, the reaction was proceeded in the presence of Cu(I) catalyst. The structure of the synthesized compounds were confirmed by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopy and elemental analysis.     

Copper Supported on the SiO2 Nanoparticle in Click Chemistry: An Alternative Catalytic System for Regioselective and One‐Pot Synthesis of 1,2,3‐Triazoles and β‐Hydroxytriazoles

In this work, readily prepared copper supported on the SiO₂ nanoparticles has been found to effectively catalyze the 1,3‐dipolar cycloaddition of a variety of azides, alkynes, epoxides and sodium azide, furnishing the corresponding 1,2,3‐triazoles and β‐hydroxytriazoles. Click reaction proceeds in short reaction times and under mild reaction conditions, and the resulting products are obtained in good yields at ambient temperature.     

A simple and efficient synthesis of novel N,N′‐bis (1H‐pyrrol‐1‐yl)‐1‐[2‐(2‐aryl‐5‐methyl‐3‐oxo‐2,4‐dihydro‐3H‐1,2,4‐triazol‐4‐yl)ethyl]‐1H‐1,2,3‐triazole‐4,5‐dicarboxamides

One‐pot reaction of 3‐aryl‐5‐methyl‐1,3,4‐oxadiazolin‐2‐ones 1a‐g with ethanolamine yielded the 4‐(2‐hydroxyethyl)‐2‐aryl‐5‐methyl‐2,4‐dihydro‐3H‐1,2,4‐triazolin‐3‐ones 2a‐g which were converted to the azido compounds 6a‐g . These azides on 1,3‐dipolar cycloaddition with DMAD afforded the dimethyl‐1‐[2‐(2‐aryl‐5‐methyl‐3‐oxo‐1,2,4‐triazol‐4‐yl)ethyl]‐1H‐1,2,3‐triazol‐4,5‐dicarboxylates 7a‐g which on conversion to bishydrazides 8a‐g and further cyclisation with 2,5‐hexanedione afforded the title compounds 9a‐g . This new short route for the so far unkown bis‐(triazolinone‐triazole)ethanes involves mild and convergent 1,3‐dipolar cycloaddition reaction yielding overall good yields of the products.     

An Elegant Synthesis of a New Class of 1‐(Substituted)‐1H‐1,2,3‐triazol‐4‐yl)methyl)diphenylphosphineoxides by Microwave Irradiation

A simple and efficient one‐pot microwave‐assisted click formation of 1‐(substituted)‐1H‐1,2,3‐triazol‐4‐yl)methyl)diphenylphosphineoxide derivatives via Huisgen regioselective [3+2]‐cycloaddition of an in situ generated organic azides and diphenyl(prop‐2‐yn‐1‐yl)phosphine oxide in highly polar DMSO‐H₂O medium. This synthetic protocol is mild, requires shorter reaction time, and afforded products in excellent yields with high regioselectivity.     

An Efficient Synthesis of Mono and Bis‐1,2,3‐triazole AZT Derivatives via Copper(I)‐catalyzed Cycloaddition

An efficient synthesis of novel mono and bis‐1,2,3‐triazoles 3′‐azido‐2′‐deoxythymidine (AZT) derivatives via copper(I)‐catalyzed 1,3‐dipolar cycloaddition reaction is described. Starting from AZT and terminal alkyne derivatives, mono and bis‐1,2,3‐triazole AZT derivatives are regioselectively obtained in good yields under mild conditions using CuSO4·5H2O and sodium ascorbate as a catalyst system, and t‐BuOH/H₂O (1:1, v/v) as a co‐solvent. The structures of these compounds were elucidated by IR, HR MS and NMR.     

1‐Thiacyclooct‐4‐yne (=5,6‐Didehydro‐3,4,7,8‐tetrahydro‐2H‐thiocin), and Its Sulfoxide and Its Sulfone

1‐Thiacyclooct‐4‐yne (=5,6‐didehydro‐3,4,7,8‐tetrahydro‐2H‐thiocin; 9 ) can be prepared from thiocan‐5‐one ( 6 ) in three steps by applying the so‐called selenadiazole method. The heterocyclic alkyne can be oxidized to the corresponding sulfoxide 16 and sulfone 17 . Due to their geometrical strain, all three cyclic alkynes show high reactivities in Diels? Alder and 1,3‐dipolar cycloadditions. Moreover, tetrathiafulvalenes can be prepared from 9 and 16 by the reaction with CS₂.     

Exploring the Border between Concerted and Two‐Step Pathways of 1,3‐Dipolar Cycloadditions of Organic Azides to Cyclic Ketene N,X‐Acetals. – Synthesis and 15N‐NMR Spectra of Zwitterions and Spirocyclic Cycloadducts

Cyclic ketene N,X‐acetals 1 are electron‐rich dipolarophiles that undergo 1,3‐dipolar cycloaddition reactions with organic azides 2 ranging from alkyl to strongly electron‐deficient azides, e.g., picryl azide ( 2L ; R¹=2,4,6‐(NO₂)₃C₆H₂) and sulfonyl azides 2M – O (R¹=XSO₂; cf. Scheme 1). Reactions of the latter with the most‐nucleophilic ketene N,N‐acetals 1A provided the first examples for two‐step HOMO(dipolarophile)–LUMO(1,3‐dipole)‐controlled 1,3‐dipolar cycloadditions via intermediate zwitterions 3 . To set the stage for an exploration of the frontier between concerted and two‐step 1,3‐dipolar cycloadditions of this type, we first describe the scope and limitations of concerted cycloadditions of 2 to 1 and delineate a number of zwitterions 3 . Alkyl azides 2A – C add exclusively to ketene N,N‐acetals that are derived from 1H‐tetrazole (see 1A ) and 1H‐imidazole (see 1B , C ), while almost all aryl azides yield cycloadducts 4 with the ketene N,X‐acetals (X=NR, O, S) employed, except for the case of extreme steric hindrance of the 1,3‐dipole (see 2E ; R¹=2,4,6‐(^tBu)₃C₆H₂). The most electron‐deficient paradigm, 2L , affords zwitterions 16D , E in the reactions with 1A , while ketene N,O‐ and N,S‐acetals furnish products of unstable intermediate cycloadducts. By tuning the electronic and steric demands of aryl azides to those of ketene N,N‐acetals 1A , we discovered new borderlines between concerted and two‐step 1,3‐dipolar cycloadditions that involve similar pairs of dipoles and dipolarophiles: 4‐Nitrophenyl azide ( 2G ) and the 2,2‐dimethylpropylidene dipolarophile 1A (R, R=H, ^tBu) gave a cycloadduct 13 H , while 2‐nitrophenyl azide ( 2 H ) and the same dipolarophile afforded a zwitterion 16A . Isopropylidene dipolarophile 1A (R=Me) reacted with both 2G and 2 H to afford cycloadducts 13G , J ) but furnished a zwitterion 16B with 2,4‐dinitrophenyl azide ( 2I) . Likewise, 1A (R=Me) reacted with the isomeric encumbered nitrophenyl azides 2J and 2K to yield a cycloadduct 13L and a zwitterion 16C , respectively. These examples suggest that, in principle, a host of such borderlines exist which can be crossed by means of small structural variations of the reactants. Eventually, we use ¹⁵N‐NMR spectroscopy for the first time to characterize spirocyclic cycloadducts 10 – 14 and 17 (Table 6), and zwitterions 16 (Table 7).     

A reusable CuSO4 · 5H2O/cationic 2,2′‐bipyridyl system catalyzed homocoupling of terminal alkynes in water

A reusable CuSO₄ · 5H₂O/cationic 2,2′‐bipyridyl system catalyzed the homocoupling reaction of terminal alkynes in water using I₂ as the additive in the presence or absence of tetrabutylammonium bromide, giving the 1,3‐diynes in good to high yields. After reaction, the residual aqueous solution could be reused several times. Copyright © 2011 John Wiley & Sons, Ltd.     

1,3‐Dipolar Cycloadditions of Ethyl 2‐Diazo‐3,3,3‐trifluoropropanoate to Alkynes and [1,5] Sigmatropic Rearrangements of the Resulting 3H‐Pyrazoles: Synthesis of Mono‐, Bis‐ and Tris(trifluoromethyl)‐Substituted Pyrazoles

The 1,3‐dipolar cycloadditions of ethyl 2‐diazo‐3,3,3‐trifluoropropanoate with electron‐rich and electron‐deficient alkynes, as well as the van Alphen? Hüttel rearrangements of the resulting 3H‐pyrazoles were investigated. These reactions led to a series of CF₃‐substituted pyrazoles in good overall yields. Phenyl‐ and diphenylacetylene proved to be unreactive, but, at high temperature, the diazoalkane and phenylacetylene furnished a cyclopropene derivative. As expected, the 1,3‐dipolar cycloaddition to the ynamine occurred much faster than those to electron‐deficient alkynes. With one exception, all cycloadditions proceeded with excellent regioselectivities. The [1,5] sigmatropic rearrangement of the primary 3H‐pyrazoles provided products with shifted acyl groups; products resulting from the migration of a CF₃ group were not detected. In agreement with literature reports, this rearrangement occurs faster with 3H‐pyrazoles bearing electron‐withdrawing substituents.     

Synthesis of Dispiro[indole‐3,2′‐pyrrolidine‐3′,2″‐pyrrolizine]‐1″,2(1H)‐diones via Azomethine Ylide 1,3‐Dipolar Cycloaddition

The 1,3‐dipolar cycloaddition of azomethine ylide generated in situ from isatin and sarcosine to 2‐arylmethylidene‐2,3‐dihydro‐1H‐pyrrolizin‐1‐ones afforded novel 1′‐methyl‐4′‐(aryl)‐1″H‐dispiro[indole‐3,2′‐pyrrolidine‐3′,2″‐pyrrolizine]‐1″,2(1H)‐diones in good yields. The structures of all the products were characterized thoroughly by NMR, infrared spectroscopy, mass spectrum, and elemental analysis.     

Synthesis of 4H‐tetrazolo[1,5‐a][1]benzazepines from the baylis‐hillman adducts of 2‐azidobenzaldehyde

Novel heterocycles, 4H‐tetrazolo[1,5‐a][1]benzazepines 6 were prepared by the intramolecular 1,3‐dipolar cycloaddition reaction of azidophenylcyanomethyl compounds 5. The latter were readily obtained from 2‐azidobenzaldehyde through the Baylis‐Hillman adducts 3 followed by acetylation to compounds 4 and nucleophilic substitution by cyanide to compounds 5.     

An Efficient Synthesis of New 5‐(1‐Aryl‐1H‐pyrazole‐4‐yl)‐1H‐tetrazoles from 1‐Aryl‐1H‐pyrazole‐4‐carbonitriles via [3 + 2] Cycloaddition Reaction

A series of new 5‐(1‐aryl‐1H‐pyrazole‐4‐yl)‐1H‐tetrazoles 4a‐l were synthesized via [3 + 2] cycloaddition reaction from 1‐aryl‐1H‐pyrazole‐4‐carbonitriles 3a‐l , sodium azide and ammonium chloride, using dimethylformamide (DMF) as solvent, in good yields: 64–85%. The structures of these newly synthesized compounds were determined from the IR, ¹H‐ and ¹³C‐NMR spectroscopic data and elemental analyses.