A new class of non-classical azapentalenes. Synthesis and c-13/n-15 NMR characterization of 2H-imidazo[1, 5-d]tetrazoles

The title compounds 6 (as well as the oxazoles 5 ) were obtained by thermolysis of 2-alkyl-5-(methoxycarbon-yldiazomethyl)tetrazoles 3 in benzonitrile. They were fully characterized by ¹H, ¹³C and ¹⁵N nmr spectroscopy.     

Synthesis of (difluoroamino)tetrazoles and [(difluoroamino)alkyl]tetrazoles

(Difluoroamino)tetrazoles were obtained by direct fluorination of 5-aminotetrazoles with gaseous fluorine. Reactions of 2-(oxoalkyl)- and 2-(hydroxyalkyl)tetrazoles with difluoroamine yielded [(difluoroamino)alkyl]tetrazoles. Deceased Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 950–952, May, 2000.     

2-alkyl-5-aryltetrazoles as hydrogen bond acceptors

The dissociation constants of the H-complexes formed by 2-alkyl-5-aryltetrazoles and p-fluorophenol in carbon tetrachloride (pK _HB 0.9–1.3) were determined by Fourier-transform IR spectroscopy. 2-Alkyl-5-aryltetrazoles were found to act as medium-strength hydrogen bond acceptors comparable with diazines. The thermodynamic parameters of the equilibrium formation of H-complex with 2-isopropyl-5-phenyltetrazole were determined. The electronic nature of substituents in the tetrazole ring only slightly affects the pK _HB values of tetrazoles.     

Tetrazoles from N-(4-dimethylaminophenyl)nitrones and hydrogen azide

The reaction of N-(4-dimethylaminophenyl)nitrones, 1 , with hydrogen azide proceeds via three distinct pathways to give a mixture of two tetrazoles, 5 and 9 , and a 2-azido-4-dimethyl-aminoaniline derivative, 6 . The proportions largely depend on the electron-withdrawing force resident in the function R attached to nitrone carbon. The formation of 5 constitutes a new synthetic approach to 1,5-disubstituted tetrazoles.     

Prototropic tautomerism of 5‐aryloxy‐1(2)H‐tetrazoles

The structure of 5‐(2,6‐dimethylphenoxy)‐1H‐ and 2H‐tetrazoles together with those of 5‐(2,6‐diisopropyl‐phenoxy)‐1H and 2H‐tetrazoles have been theoretically studied including absolute shieldings and energies. The conclusion of these studies is that a slow tautomerism between 1H‐ and 2H‐tetrazoles cannot explain the experimental observations reported recently in the literature. Copyright © 2012 John Wiley & Sons, Ltd.     

Concise route to a series of novel 3-(tetrazol-5-yl)quinoxalin-2(1H)-ones

This report presents a novel three step solution phase protocol to synthesize 3-(tetrazol-5-yl)quinoxalin-2(1H)-ones. The strategy utilizes ethyl glyoxalate and mono-N-Boc-protected-o-phenylenediamine derivatives in the Ugi-Azide multi-component reaction (MCR) to generate a unique 1,5-disubstituted tetrazole. Subsequent acid treatment stimulates a simultaneous Boc deprotection and intramolecular cyclization leading to bis-3,4-dihydroquinoxalinone tetrazoles. Direct oxidation using a stable solid-phase radical catalyst (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) with ceric ammonium nitrate (CAN) in catalytic fashion initiating aerobic oxidation, completes the entire procedure to generate a series of original unique bis-quinoxalinone tetrazoles. The method was also expanded to produce a bis-benzodiazepine tetrazole.     

A new route to the improved synthesis of 1-(alkoxymethyl)-5-alkyl-6-(arylselenenyl)uracils

A new route to C-6-selenenyl analogs of compound 1a from 5-alkyl-6-chlorouracils 6a-b has been described. A mild and highly efficient synthesis of 1-(alkoxymethyl)-5-alkyl-6-(arylselenenyl)uracils 8a-e has been accomplished from 6a-b in good yields using a two step procedure. Silylation of 5-alkyl-6-chlorouracils 6a-b using N,O-bis(trimethylsilyl)acetamide followed by regioselective alkylation of the silylated intermediate with ethyl or benzyl chloromethyl ether in dichloromethane afforded the desired 1-(alkoxymethyl)-5-alkyl-6-chlorouracils 7a-d in 88–94% yields. Compounds 7a-d readily underwent addition-elimination reaction with an appropriate arylselenol in the presence of ethanolic sodium hyroxide to produce the corresponding 1-(alkoxymethyl)-5-alkyl-6-(arylselenenyl)uracils 8a-e in excellent yields (94–99%).     

Equilibria of the 5-substituted-1,2-acylated tetrazoles and imidoyl azides

Equilibrium of acylated-5-alkyloxy (aryloxy) tetrazoles and acylated-imidoyl azides was measured by (1)H NMR and/or IR spectroscopy. In nonpolar solvents the relatively weakly electron-withdrawing acyl group (CO(2)CH(3)) favored acylation at the 2-position of the 5-substituted tetrazoles. Moderately electron-withdrawing groups (CO(2)CH(2)CCl(3), CO(2)CCl(3)) move the equilibrium to the side of 1-acyl-5-substituted tetrazole. Strong electron-withdrawing groups (CN, SO(2)CH(3), SO(2)CF(3)) favored the formation of the azide. The rate of isomerization of tetrazoles and the azide increases at higher concentrations and polarity of the solvent. In solid phase or in the nonpolar solvent (diethyl ether), only one of the three isomers is present, its structure depending on the nature of the substituents at the 1 or 2 positions of tetrazoles.     

Formation of organotinnitrogen bonds : VI. The intermolecular association of 2-(tri-n-butylstannyl)-tetrazoles in solution

The intermolecular association of 2-(tri-n-butylstannyl)tetrazoles in benzene solution has been evaluated by the measurement of the apparent molecular weight. The degree of the association is highly dependent on the steric effect of the 5-substituent of the tetrazoles. Low temperature NMR spectra of CDCl₃ solutions of 2-(tri-n-butylstannyl)-5-phenyltetrazole and -5-(p-nitrophenyl)tetrazole displayed temperature- and concentration-dependencies. As the temperature decreases, the benzene and tetrazole rings become less coplanar. This may be attributed to the closer polymeric association of the 1-nitrogen to tin at low temperature. The intermolecular associated form of 2-(tri-n-butylstannyl)tetrazoles in less polar solvents such as benzene and chloroform is confirmed as a 1,3-structure (A).     

The preparation of 5-(2-bromoethyl)-2-iminooxazolidines via the von braun cyanogen bromide reaction

The reaction of certain 1-alkyl-3-pyrrolidinols with cyanogen bromide in ether solution produced 3-alkyl-5-(2-bromoethyl)-2-iminooxazolidines. 5-(2-Bromoethyl)-2-ethyl-2-imino-5-phenyloxazolidine was tested for and found devoid of anorectic activity.     

Theoretical Study on Tetrazole and its Derivatives (5) Ab Initio Study on Nitro Derivatives of Tetrazole

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Regioselective synthesis of 1-alkyl-5-(indol-3-yl- and -2-yl)pyrrolidin-2-ones from available reagents

The reaction under mild conditions of 1-alkyl-5-hydroxypyrrolidin-2-ones with different indoles having a free 3 position leads exclusively to 1-alkyl-5-(indol-3-yl)pyrrolidin-2-ones but if position 3 is occupied to 1-alkyl-5-(indol-2-yl)pyrrolidin-2-ones.     

One-Pot Preparation Method of 5-Alkyl-3-(benzo)pyridyl-1,2,4-triazines

Russian Journal of Organic Chemistry - Convenient one-pot method was developed for the preparation of 5-alkyl-3-(2-pyridyl)-, 5-alkyl-3-(4-pyridyl)- or 5-alkyl-3-(quinolin-2-yl)-1,2,4-triazines in...     

Quantum-Chemical Study of the Relative Stability of N-Substituted Tetrazole Isomers

The enthalpies of formation and total energies of a series of 1- and 2-substituted tetrazoles in the gas phase and in solution were calculated by MNDO and AM1 semiempirical methods and by a set of nonempirical procedures. The effect of solvent on the relative stability of N-substituted tetrazoles was estimated in terms of the PCM, SM5, and SCRF models. The possibility for isomerization of N-substituted tetrazoles, depending on the substituent in position 1 or 2, was studied at the MP2/6-31G*//HF/6-31G* level. According to the results of nonempirical calculations, 2-substituted tetrazoles are more stable in the gas phase, in keeping with the experimental data for the corresponding isomers. The solvent nature is an important factor affecting isomerization of N-substituted tetrazoles: Rise in the solvent polarity leads to displacement of the equilibrium toward 1-substituted isomers.     

Synthesis and resolution of 2-arylalkyl-2-(tetrazol-5-yl)-N-arylalkyl-carboxamides. A new class of chiral sterically hindered tetrazole derivatives

Chiral, racemic 2-arylalkyl-2-(tetrazol-5-yl)-N-arylalkylcarboxamides 3 were conveniently prepared from ethyl cyanoacetate in four steps. The synthetic methodology developed is a facile way of introducing bulky substituents into a peptide-like framework, affording intermediate α-arylalkyl-α-amidonitriles. These nitriles were sufficiently activated to give, upon treatment with ammonium azide in dimethylformamide at 145° for twenty-four to thirty hours, the corresponding tetrazoles in good yields. It has been determined that an optically pure α-arylalkyl-α-amidonitrile epimerized to give diastereomeric products under the above conditions. A procedure for the fractional crystallization of the (S)-(-)-α-methylbenzylamine salts 4 of the tetrazoles to give the optically enriched tetrazoles 5 was also developed.     

Mechanism of the monomolecular thermal decomposition of tetrazole and 5-substituted tetrazoles

The kinetic parameters of the thermal decomposition of tetrazole and 5-alkyl- and 5-aryl-substituted tetrazoles in melts of neat substances and in nitrobenzene solutions have been determined using the manometric method. The limiting stages of the monomolecular decomposition, which determine the observed rate of nitrogen formation, include the fast reversible transformation of the lH- and 2H-forms and the reversible opening of the 2H-form followed by the formation and subsequent cleavage of the corresponding intermediate diazo compound.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2216–2219, September, 1996.     

Synthesis of mesomorphic 2-alkyl-5-(p-cyanophenyl)pyridines

A new series of liquid-crystal derivatives of 2-alkyl-5-(p-cyanophenyl)pyridines were obtained by halogenation of 2-alkyl-5-phenylpyridines under the conditions of the Birckenbach-Gubo-Waters reaction with subsequent conversion of the 2-alkyl-5-(p-bromo- or iodophenyl) pyridines to the cyano derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 85–88, January, 1981.     

Synthesis of 2-(4-cyanophenyl)-5-(4-n-alkyl- and alkoxyphenyl) pyridines

New liquid-crystalline 2-(4-cyanophenyl)-5-(4-alkyl- and alkoxyphenyl)pyridines were obtained by condensation of 1-dimethylamino-3-dimethylimmonia-2-(4-alkyl- or alkoxyphenyl)-1-propene perchlorates with 4-cyanoacetophenone and subsequent conversion of the 1-dimethylamino-2-(p-alkyl- or alkoxyphenyl)-4-(p-cyanobenzoyl)-1,3-butadienes to 5-(4-alkyl- or alkoxyphenyl)-2-(4-cyanophenyl)pyrylium perchlorates and refluxing of the latter with ammonium acetate in acetic acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1392–1394, October, 1985.     

Efficient synthesis of 2,5-disubstituted tetrazoles via the Cu2O-catalyzed aerobic oxidative direct cross-coupling of N-H free tetrazoles with boronic acids

We present a new protocol that allows for the synthesis of 2,5-disubstituted tetrazoles via the direct coupling of N-H free tetrazoles and low toxic boronic acids in the presence of only a catalytic amount of Cu(2)O (5 mol%) as catalyst and 1 atm of environmentally benign O(2) as oxidant, without the need for other additives. This method represents a simple, green, and atom-efficient synthesis of 2,5-disubstituted tetrazoles.     

Syntheses of 5‐(3‐Arylsydnon‐4‐yl)Tetrazole Derivatives

3‐Arylsydnone‐4‐carbohydroximic acid chlorides ( 1 ) could react with sodium azide to produce the corresponding 3‐arylsydnone‐4‐carbazidoximes ( 2 ), but not 1‐hydroxytetrazoles 3 . Treatment of 3‐arylsydnone‐4‐carbazidoximes ( 2 ) with acid chlorides such as acetyl chloride ( 4a ), propionyl chloride ( 4b ) and benzoyl chloride ( 4c ) in the presence of excess triethylamine generated the derivatives of the azidoximes 5 . To obtain the desired tetrazoles, the azidoximes 2 should first cyclize directly with acetyl chloride ( 4a ) or propionyl chloride ( 4b ) to afford the acetyl or propionyl derivatives 6 . The cyclized tetrazole derivatives 6 underwent deacylation upon heating in ethanol to give 1‐hydroxy‐5‐(3‐arylsydnon‐4‐yl)tetrazoles ( 3 ).