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[3+2]‐Cycloaddition reactions of 3‐trifluoromethyl‐2H‐thiete 1,1‐dioxide, 4(5)‐trifluoromethyl‐2,3‐dihydrothiophene 1,1‐dioxides and 5(6)‐trifluoromethyl‐3,4‐dihydro‐2H‐thiopyrane 1,1‐dioxides with diazomethane proceed with the formation of regioisomeric mixtures of corresponding dihydropyrazole‐fused cycloadducts. Reactions of 3‐trifluoromethyl‐2H‐thiete 1,1‐dioxide with ethyl diazoacetate and in situ generated 2,2,2‐trifluorodiazoethane lead to the regioselective formation of pyrazolino‐sultine derivatives via rearrangement of initially formed pyrazoline‐fused thietane 1,1‐dioxides. Treatment of 3‐trifluoromethyl‐2H‐thiete 1,1‐dioxide and 4‐trifluoromethyl‐2,3‐dihydro‐thiophene 1,1‐dioxide with in situ generated N‐phenyl nitrilimines gives rise to dihydropyrazole‐ thietane 1,1‐dioxides and tetrahydrothiophene 1,1‐dioxides, respectively, in a regioselective fashion. [ABSTRACT FROM AUTHOR]

1,2,4‐triazolo‐[4,3‐a]pyrazine was prepared via a two‐step electrochemical, photochemical process. First, a 5‐substituted tetrazole is electrochemically coupled to 2,6‐dimethoxypyrazine to yield 1,5‐ and 2,5‐ disubstituted tetrazoles. Subsequent photochemical excitation of the 2,5‐disubstituted tetrazole species using an ultraviolet lamp releases nitrogen gas and produces a short‐lived nitrilimine intermediate. Subsequent cyclization of the nitrilimine intermediate yields a 1,2,4‐triazolo‐[4,3‐a]pyrazine backbone. The scope of this reaction was explored using various tetrazoles and pyrazines. Materials produced were identified using chemical analytical techniques and computationally studied for potential application as an insensitive energetic material. [ABSTRACT FROM AUTHOR]

We investigated the reactivity of different substituted nitrylimine-type three atom components (TACs) in [3+2] cycloaddition (32CAs) reactions with electrophilically activated nitroethenes within molecular electron density theory (MEDT). In parallel research, the molecular mechanism of the considered transformation was examined through analysis of all possible reaction channels and full optimization of all critical structures. In particular, the existence of zwitterionic intermediates on reaction paths was verified. On the basis of the bonding evolution theory (BET), the mechanism of the 32CA reaction between C,N-diphenylnitrylimine and (E)-2-phenyl-1-cyano-1-nitroethene should be treated as a one-step two-stage mechanism.

The 32CA cycloaddition reactions of the hydroxyparthenolide with nitrilimine have been studied using molecular electron density theory. The reactivity indices, activation and reaction energies are calculated at the B3LYP/6-31(d) level. The presence of two double bonds in hydroxyparthenolide gives six reaction pathways for this cycloaddition. The reaction proceeds via a one-step asynchronous mechanism with a nonpolar character, and an analysis of conceptual DFT indices explains the nonpolar character of this cycloaddition reaction. The calculations of the activation and reaction energies show that this cyclization reaction takes place on the C1=C2 double bond, which indicates that this cycloaddition reaction is chemospecific and regiospecific in full conformity with the experimental results. The reorganization of electrons along the most preferred pathway of the 32CA cycloaddition reaction between hydroxyparthenolide and nitrilimine was investigated using topological analysis of the electron localization function (ELF). ELF analysis revealed that this reaction proceeds through a two-stage one-step mechanism. [ABSTRACT FROM AUTHOR]

We investigated the reactivity of different substituted nitrylimine-type three atom components (TACs) in [3+2] cycloaddition (32CAs) reactions with electrophilically activated nitroethenes within molecular electron density theory (MEDT). In parallel research, the molecular mechanism of the considered transformation was examined through analysis of all possible reaction channels and full optimization of all critical structures. In particular, the existence of zwitterionic intermediates on reaction paths was verified. On the basis of the bonding evolution theory (BET), the mechanism of the 32CA reaction between C,N-diphenylnitrylimine and (E)-2-phenyl-1-cyano-1-nitroethene should be treated as a one-step two-stage mechanism. [ABSTRACT FROM AUTHOR]

Reaction of the Ga(I) compound NacNacGa (9) with the diazo compound N2CHSiMe3 affords the nitrilimine compound NacNacGa(N‐NCSiMe3)(CH2SiMe3) (10). Carrying out this reaction in the presence of pyridine does not lead to C−H activation on the transient alkylidene NacNacGa=CHSiMe3 but generates a metallated diazo species NacNacGa(NHN=CHSiMe3)(CN2SiMe3) (13) that further rearranges into the isonitrile compound NacNacGa(NHN=CHSiMe3)(N(NC)SiMe3) (15). Reactions of 10 with the silane H3SiPh and the borane HBcat furnished products of 1,3 addition to the nitrilimine moiety NacNacGa{N(ERn)NCSiMe3}(CH2SiMe3), whereas reaction with the diborane B2cat2 gave the product of formal nitrene insertion into the B−B bond. DFT calculations suggest that the interaction of 9 with N2CHSiMe3 proceeds through intermediate formation of an alkylidene compound that undergoes CH activation with a second molecule of N2CHSiMe3. Insertion into the B−B bond likely proceeds through an initial 1,3‐addition of the diborane, followed by boryl migration to the former nitrene center. [ABSTRACT FROM AUTHOR]

1,3-Dipolar cycloaddition reactions of 3,3,3-trifluoropropene derivatives containing a sulfonyl, sulfamide, or sulfoximine substituent in position 1 with diazomethane proceed with the formation of 3-substituted 4-(trifluoromethyl)-4,5-dihydro-1H-pyrazoles and 3-(trifluoromethyl)-1H-pyrazole, whereas reactions with ethyl diazoacetate and 2,2,2-trifluorodiazoethane lead to the formation of isomeric 5(3)-substituted 4-trifluoromethyl-3,4(4,5)-dihydro-2(1)H-pyrazoles and 4-substituted 5-(trifluoromethyl)-4,5-dihydro-1Hpyrazoles, the stability of which depends on the nature of the heteroatomic substituent. The cycloaddition of 1-sulfonyl- and 1-sulfamoylsubstituted derivatives of 3,3,3-trifluoropropene to C-carbethoxy-N-phenylnitrilimine gives rise to 4-substituted ethyl 1-phenyl-5-(trifluoromethyl)-4,5-dihydro-1H-pyrazole-3-carboxylates and ethyl 1-phenyl-4-(trifluoromethyl)-1H-pyrazole-3-carboxylate. [ABSTRACT FROM AUTHOR]

A regioselective 1,3-dipolar cycloaddition of nitrilimines, generated from hydrazonoyl chlorides, with both C = C double bonds of cyclopentadienone moiety of cyclopenta[a]acenaphthylen-8-ones in the presence of Et3N is described. This dual cycloaddition reaction affords a nearly 3:2 mixture of symmetrical and unsymmetrical hexacyclic bis-dihydropyrazol derivatives in good yields. The stereochemistry of diethyl 3,7-bis(4-chlorophenyl)-4-oxo-1,5-diphenyl-1H-naphtho[1′,8′:4,5,6]pentaleno[1,6a-c:3a,3-c′]dipyrazole-3a,4a(4H,5H)-dicarboxylate was established by X-ray crystallography. [ABSTRACT FROM AUTHOR]

The 1,3-dipolar cycloaddition of nitrilimine, generated in situ from (Z)-N-aryl-2-oxopropanehydrazonoyl bromide and Et3N, to 3-arylpyrrolo[ 1,2-a]pyrazine afforded novel 1-(1,5-diaryl-1,10b-dihydropyrrolo[1,2-a][1,2,4]triazolo[3,4-c]pyrazin-3-yl)ethanones in moderate yields. The structures of all the products were characterized thoroughly by NMR, IR, and HRMS. [ABSTRACT FROM AUTHOR]

In this work, we report the synthesis of new pyrazole derivatives bearing amide and sulfonamide frameworks from aza-aurones. Firstly, the intermediate spiropyrazolines were obtained through a highly regioselective 1,3-dipolar cycloaddition of nitrilimines with aza-aurones. Subsequently, the obtained cycloadducts were subjected to hydrochloric acid in hot ethanol which conducts to 5-(2-aminobenzoyl)-3,4-diaryl-1-phenylpyrazoles. Finally, the target compounds were obtained separately by the action of acetic anhydride, benzoyl chloride and tosyl chloride on the intermediates 2-aminobenzoylpyrazoles, respectively. Structures of all the synthesized compounds were established using IR, 1H NMR and 13C NMR and mass spectroscopy. Synthesis and characterization of novel heterocyclic systems encompassing pyrazole derivatives from aza-aurones are reported. The synthetic routes used in this work are efficient and relevant, involving the 1,3-dipolar cycloaddition and alkylation reactions. The outcomes show that spectroscopic data fit the structure of all synthesized compounds. [ABSTRACT FROM AUTHOR]

Gelatin is a costless polypeptide material of natural origin, able to form hydrogels that are potentially useful in biomaterial scaffold design for drug delivery, cell cultures, and tissue engineering. However, gelatin hydrogels are unstable at physiological conditions, losing their features only after a few minutes at 37 °C. Accordingly, treatments to address this issue are of great interest. In the present work, we propose for the first time the use of bi- and trifunctional tetrazoles, most of them unknown to date, for photoinduced gelatin cross-linking towards the production of physiologically stable hydrogels. Indeed, after UV-B irradiation, aryl tetrazoles generate a nitrilimine intermediate that is reactive towards different functionalities, some of them constitutively present in the amino acid side chains of gelatin. The efficacy of the treatment strictly depends on the structure of the cross-linking agent used, and substantial improved stability was observed by switching from bifunctional to trifunctional cross-linkers.

Novel 4'-aryl-1,2',5'-triphenyl-2',4',6,7-tetrahydrospiro[indazole-5,3'-pyrazol]-4(1H)-ones have been synthesized in moderate yields by 1,3-dipolar cycloaddition of 5-arylmethylidene-1-phenyl-1,5,6,7-tetrahydro-4H-indazol-4-ones and diphenylnitrilimine, generated in situ from N-phenylbenzohydrazonoyl chloride and triethylamine. According to structural analyses by NMR spectroscopy and single crystal X-ray diffraction method, the reaction proceeds regioselectively affording products with C(5)-C(3') connectivity at the spiro center. [ABSTRACT FROM AUTHOR]

The regioselectivity of the reaction between phenyldiazen-1-ium-1-ylidene p-tolyl methanide and ethyl 4-benzoyl-4H-benzo[1,4]oxazine-2-carboxylate were studied by means of the DFT/B3LYP method coupled by the 6-31g(d) basis and MP2 in connection with 6-31G(d) and 6-31G+(d,p) basis set. The mechanism of this regioselectif reaction has performed by transition state optimization, evaluation of the potential energy surface, calculation of IRC and reactivity indices. Location and verification of minima and transition structures have been realized by using the Berny's algorithm. The process of formation of the two regioisomers is achieved through concerted and asynchronous mechanism. The results are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Abstract: The double 1,3-dipolar cycloaddition reaction between nitrilimine and allenoate, experimentally investigated by Guo and co-workers, was theoretically studied at the B3LYP/6-311G** and wB97XD/6-311G** computational levels in both gas phase and dichloromethane solution. The results indicated that the formation of the experimentally reported product is clearly explained by the analysis of the calculated Fukui function reactivity indices as well as transition states studies. Frontier molecular orbitals analysis showed that the HOMO orbital of nitrilimine as donor is also the frontier effective-for-reaction molecular orbital (FERMO). Finally, on the basis of the Wiberg bond indexes and AIM analysis, it was found that all of the reactive channels proceed through an asynchronous concerted mechanism.Graphical abstract: [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of a new series of 1,3,5-trisubstituted-1,2,4-triazoles by 1,3-dipolar cycloaddition reaction of C-phenyl-aminocarbonyl-N-arylnitrilimines with guanidine derivatives. The structures of the newly synthesized compounds were elucidated by spectral methods (IR, 1H NMR, 13C NMR and MS spectroscopy) and elemental analysis. The microbial features of the synthesized compounds were studied using well-established methods from the literature.

Nitrilimine generated by photolysis of diaryltetrazole in aqueous phase under mild conditions was trapped by nucleophiles including amines and thioalcohols. The representative products were characterized, while products with all 20 natural amino acids and a peptide were observed by MALDI-TOF mass spectroscopy. Competitive studies showed that this reaction also occurred in the presence of acrylamide. These results provided new information for understanding the potential side reactions when tetrazole-alkene pairs were used as a bioorthogonal reaction in labeling proteins and related studies in buffered systems.

Conventional frontier molecular orbital theory is not able to satisfactorily explain the regioselectivity outcome of the nitrilimine-alkene cycloaddition. We considered that conceptual density functional theory (DFT) could be an effective theoretical framework to rationalize the regioselectivity of the title reaction. Several nitrilimine-alkene cycloadditions were analyzed, for which we could find regioselectivity data in the literature. We computed DFT reactivity indices at the B3LYP/6-311G(2d,p)//B3LYP/6-31G(d,p) and employed the grand potential stabilization criterion to calculate the preferred regioisomer. Experimental and calculated regioselectivity agree in the vast majority of cases. It was concluded that predominance of a single regioisomer can be obtained by maximizing (i) the chemical potential difference between nitrilimine and alkene and (ii) the local softness difference between the reactive atomic sites within each reactant. Such maximization can be achieved by carefully selecting the substituents on both reactants. [ABSTRACT FROM AUTHOR]

Several 1,3-diaryl-5-(cyano-, aminocarbonyl- and ethoxycarbonyl-)-2-pyrazoline, pyrrolo[3,4-c]pyrazole-4,6-dione and 1,3,4,5-tetraaryl-2-pyrazoline derivativeswere prepared by the reaction of nitrilimine with different dipolarophilic reagents. The newcompounds were characterized using IR, 1H-NMR, 13C-NMR and mass spectra. Biologicalscreening of some compounds is reported.

Conventional frontier molecular orbital theory is not able to satisfactorily explain the regioselectivity outcome of the nitrilimine–alkene cycloaddition. We considered that conceptual density functional theory (DFT) could be an effective theoretical framework to rationalize the regioselectivity of the title reaction. Several nitrilimine–alkene cycloadditions were analyzed, for which we could find regioselectivity data in the literature. We computed DFT reactivity indices at the B3LYP/6-311G(2d,p)//B3LYP/6-31G(d,p) and employed the grand potential stabilization criterion to calculate the preferred regioisomer. Experimental and calculated regioselectivity agree in the vast majority of cases. It was concluded that predominance of a single regioisomer can be obtained by maximizing (i) the chemical potential difference between nitrilimine and alkene and (ii) the local softness difference between the reactive atomic sites within each reactant. Such maximization can be achieved by carefully selecting the substituents on both reactants.

[Display omitted] In the presence of 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as an oxidizer, the domino [3 + 2] cycloaddition reaction of aldohydrazones with 2-arylidene-1,3-indnaediones or 5-arylidene-1,3-dimethylbarbituric acids in acetonitrile at 80 °C afforded functionalized spiro[indene-2,4′-pyrazoles]-1,3-diones or 2,3,7,9-tetraazaspiro[4.5]dec-1-ene-6,8,10-triones in satisfactory yields. This reaction was believed to proceed with in situ generation of reactive 1,3-dipolar nitrilimine and its sequential 1,3-dipolar cycloaddition reaction with cyclic dipolarophiles. Thus, a new convenient synthetic method for the active dipolar nitrilimine was successfully developed. [ABSTRACT FROM AUTHOR]

The 1,3-dipolar cycloaddition of nitrilimine, generated in situ from N'-phenylbenzohydrazonoyl chloride and triethylamine, to 7-arylmethylidene-6,7-dihydroindolizin-8(5H)-one afforded novel 4'-aryl-2',5'-diphenyl-2',4',5,6-tetrahydro-8H-spiro(indolazine-7,3'- pyrazol)-8-ones in moderate yields. The structures of all the products were characterised thoroughly by NMR, infrared spectroscopy and HRMS. The structure and stereochemistry was confirmed by x-ray diffraction analysis [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of a new series of 1,3,5-trisubstituted-1,2,4-triazoles by 1,3-dipolar cycloaddition reaction of C -phenyl-aminocarbonyl- N -arylnitrilimines with guanidine derivatives. The structures of the newly synthesized compounds were elucidated by spectral methods (IR, 1 H NMR, 13 C NMR and MS spectroscopy) and elemental analysis. The microbial features of the synthesized compounds were studied using well-established methods from the literature. [ABSTRACT FROM AUTHOR]

Abstract: Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles. [Copyright &y& Elsevier]

Nitrilimine generated by photolysis of diaryltetrazole in aqueous phase under mild conditions was trapped by nucleophiles including amines and thioalcohols. The representative products were characterized, while products with all 20 natural amino acids and a peptide were observed by MALDI-TOF mass spectroscopy. Competitive studies showed that this reaction also occurred in the presence of acrylamide. These results provided new information for understanding the potential side reactions when tetrazole-alkene pairs were used as a bioorthogonal reaction in labeling proteins and related studies in buffered systems. [ABSTRACT FROM AUTHOR]

1,3-Dipolar cycloaddition of nitrilimines 3 with N-benzyl maleimide 4 has provided 5-benzyl-1-(2′,4′-dibromophenyl)-3-(4″-substituted phenyl)-3a,4,6,6a-tetrahydro-1 H,5 H-pyrrolo[3,4- c]pyrazole-4,6-dione derivatives 5 in excellent yield as the only isomer through a concerted pathway. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

1,3-dipolar cycloaddition between acrylonitrile and methylmethacrylate with two N-(4-bromophenyl)-C-(4-substituted) nitrilimines which were generated in situ afforded the new pyrazoles. The regioselectivity and reactivity of these reactions has been investigated on the basis of density functional theory (DFT)-based reactivity indexes and activation energy calculations. The theoretical 13C NMR chemical shifts of the cycloadducts which were obtained by GIAO method were comparable with the observed values. [ABSTRACT FROM AUTHOR]

Abstract: 2-Aryl-5-acroleinyl-1,2,3,4-tetrazoles (1a–d) and 2-aryl-5-butadienyl-1,2,3,4-tetrazoles (1e–g) were subjected to flash vacuum pyrolysis. Acroleinyl derivatives resulted in nitrogen extrusion to give nitrilimines followed by ring closure to give the corresponding indazoles 3a–d in good yields. On the other hand, butadiene derivatives underwent ring fragmentation to give p-substituted anilines without formation of the expected indazoles. Differences between thermal behaviour of 2-(4-chlorophenyl)-5-acroleinyl-1,2,3,4-tetrazole (1c) and 1-(4-chlorophenyl)-4-acroleinyl-1,2,3-triazole (2) were studied in details. DFT calculations have been used to examine the nitrilimine and carbene nature of the intermediates involved in the thermal reactions of azolyl derivatives. [Copyright &y& Elsevier]

Eleven novel dihydropyrrolo[3,4- c]pyrazole derivatives were obtained by the reaction of chiral (1 R)- N-(1-phenylethyl)maleimide and C,N-aryl-substituted nitrilimines. The reaction afforded the cycloadducts as a regioisomeric mixture which can be separable in some cases. The structure and stereochemistry of cycloadducts were assigned on the basis of infrared (IR), H and C nuclear magnetic resonance (NMR), mass and X-ray spectra, optical rotation measurements, and CHN analyses. Graphical Abstract: [Figure not available: see fulltext.]. [ABSTRACT FROM AUTHOR]

Abstract: An efficient 1,3-dipolar cycloaddition method was performed for the synthesis of a series of monofluoro- and trifluoromethane-3,5-disubstituted 1,2,4-triazoles. This efficient cycloaddition method was to react hydrazonoyl hydrochlorides with a series of aldehydes in the presence of NEt3 as catalytic basic agent to provide the corresponding product in 28–94%. Their growth inhibitory results against cancer cells indicated that some of the fluorine- and trifluoromethane-containing compounds could effectively inhibit the growth of NCI-H226 and T-cell leukemia (Jurkat) cells. Among the compounds, trifluoromethane-containing 1,2,4-triazoles possessed the five-membered ring groups on the C-5 position of the triazolic ring, including cyclopentyl, 3-furyl, 3-thienyl, and 2-pyrrolyl, possessed the significant inhibitory activity for NCI-H226 cancer cells. [Copyright &y& Elsevier]

A series of 5-substituted 1-methyl-3-phenyl-4,5-dihydro-1,2,4-triazin-6-ones was prepared by the reaction of α-amino acid methyl esters with appropriate nitrilimines and treated with phosphorus pentasulfide to afford 5-substituted 1-methyl-3-phenyl-4,5-dihydro-1,2,4-triazin-6-thiones. When 1,2,4-triazin-6-thiones were allowed to react with nitrilimine, the novel 4,6-dimethyl-2,8-di-phenyl-10-substituted-1-thia-3,4,6,7,9-pentaazaspiro[4.5]dec-2,7-dienes were obtained and confirmed by their elemental analyses and spectral data. Some of the synthesized compounds were tested in vitro for their antimicrobial activity. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT [image omitted] [ABSTRACT FROM AUTHOR]

Abstract: A new ‘one-flask’ synthesis of 3,5-disubstituted 1,2,4-triazoles has successfully been developed to synthesize a series of 3,5-disubstituted 1,2,4-triazoles. The transformation involves the 1,3-dipolar cycloaddition reaction of hydrazonoyl hydrochlorides with oxime intermediates prepared from aldehydes with hydroxylamine hydrochloride in the presence of excess amount of triethylamine. In this ‘one-flask’ 1,3-dipolar reaction, hydrazonoyl hydrochlorides was concerned as the masked 1,3-dipole nitrilimine under basic condition. Furthermore, this newly developed methodology can be applied to various aldehyde substrates including aliphatic, cyclic aliphatic, aromatic, and heterocyclic aldehydes. [Copyright &y& Elsevier]

Abstract: 1,3-Dipolar cycloaddition of in situ generated C,N-diaryl nitrilimines to 2-methyl-2-vinyl oxirane gives rise to the regioselective formation of novel 5-(2-methyloxiranyl)-4,5-dihydropyrazole derivatives in moderate to good yields. The structures and stereochemistries of the new cycloadducts were confirmed by spectroscopic/physical methods including X-ray diffraction data. [Copyright &y& Elsevier]

Twenty-nine novel bis(dihydropyrrolo[3,4- c]pyrazole) derivatives were obtained by reacting C,N-phenyl-substituted nitrilimines generated in situ from corresponding hydrazonyl chlorides with bismaleimides. The structures were elucidated by physical and spectroscopic methods [m.p., R, infrared (IR), H nuclear magnetic resonance (NMR), C NMR, correlation spectroscopy (COSY), heteronuclear correlation (HETCOR), nuclear Overhauser effect (NOE), and high-resolution mass spectrometry (HRMS)]. Also, Hammett correlation graphs were obtained between Hammett constants σ and λ values of bis(pyrrolopyrazoles) carrying p-substituted phenyl-ring-bearing electron-withdrawing and electron-donating groups and discussed in terms of substituent effects. Graphical Abstract: [Figure not available: see fulltext.]. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of vinyl acetate (3), 2-propyne-1-ol (4) and styrene (5) as dipolarphiles with N-[4-nitrophenyl]-C-[2-furyl] nitrilimine which was generated in situ has been shown to afford 3-(furan-2-yl)-1-(4-nitrophenyl)-4,5-dihydro-1H-pyrazol-5-yl acetate (6), (3-(furan-2-yl)-1-(4-nitrophenyl)-1H-pyrazol-5-yl)methanol (8) and 3-(furan-2-yl)-1-(4-nitrophenyl)-5-phenyl-4,5-dihydro-1H-pyrazole (10). Reactivity and regiochemistry of these reactions were investigated using DFT-based reactivity indexes. [Copyright &y& Elsevier]

A new series of 1,3,4,6-tetrasubstituted 1,2,4,5-tetrazines were synthesized from the cycloaddition reaction of methylhydrazones of alkanal and cycloalkanal with appropriate hydrazonoyl halides. [ABSTRACT FROM AUTHOR]