Tetrazoles thermolysis

Tetrazoles, tautomerism and acid-base properties of 80KGS867. Tetrazoles, thermolysis and mass spectral fragmentation of 85KGS723. 

UV spectra, 5, 798 synthesis, 5, 833 thermolysis, 5, 812 Tetrazole, 5-amino-2-methyl-methylation, 5, 818 Tetrazole, 2-aryl-5-substituted quatemization, 5, 815 Tetrazole, 5-aryl-acidity, 5, 816... 

Ar-Arylbenzimidoyl)tetrazoles t, prepared from JV-arylbenzimidoyl chlorides and 5-(dimethylamino)- or 5-aryltetrazole, give 3//-l,3,4-benzotriazepines 4 on thermolysis. It has been proposed that the reaction proceeds by way of the dipolar compounds 2, which undergo [l,7]-antarafacial 871-electrocyclization to 3. The process is completed by a symmetry-allowed [1.5]-hydrogen shift. Selected examples are given.349-350... 

Alkenyl-substituted diarylnitrilimines 325, generated by photolysis or thermolysis of corresponding tetrazoles 324, undergo a regioselective INIC reaction to yield fused 2-pyrazolines (Scheme 34) [93]. Similarly, with alkynyl derivatives... 

Houghton, P. G. et al., J. Chem. Soc., Chem. Comm., 1979, 771 Thermolysis of the undiluted tetrazole is violent, but controlled sand or in solution. 

The thermolysis of l-([l,3,4]thiadiazol-2-yl)tetrazoles 133 gives rise to the loss of dinitrogen from the tetrazole ring and the formation of 2,6-diaryl[l,2,4]triazolo[5,l+][l,3,4]thiadiazoles 71 (Equation 39) <1985IJB908, 1990FA953>. (For another synthesis of compounds 71, see Section 11.07.8.1.5.)... 

Wentrup and co-workers have carried out systematic flash vacuum thermolysis studies with a series of fused tetrazoles. Investigations of the isomeric tetrazolo[l,5- ]pyrazine 17 and tetrazolo[l,5-f]pyrimidine 20 showed that, in both cases, ring contraction takes place to afford imidazoles in high yields, but isotope labeling experiments revealed that the mechanisms of the openings of the two ring systems are different <2002JOC8538>. 

The thermolysis of tetrazoles 168 may result in the formation of mono-and bicyclic heterocycles 169. 

The tetrazole procedure that has been proved to be of value in the thiazolo[3,2-6][l,2,4]triazole series (see Section VIII) has also been applied in this field. V-Acylated 2-aminothiadiazoles 193 on treatment with phosphorus pentachloride (120°C) and subsequently with sodium azide (aqueous acetone) yield tetrazoles 194. Thermolysis in tetraline (160-180°C) gives the heterocycles 195 in moderate yields [85IJC(B)908 WFA953]. 

Thermolysis of tetrazole oximes (478) in a suitable hydrocarbon solvent, or pyrolysis without it, produces 3,5-disubstituted 1,2,4-oxadiazoles (480) (Scheme 75) (81BSB193 87BSB675 91MIP137367). in the case of 5-unsubstituted tetrazoles (478 R = H), the reaction goes by two concomitant pathways, which imply elimination of hydrazoic acid or nitrogen. 

Tetrazoles (130) and nitrile oxides form mixtures of isomers (131) and (132) (Scheme 59). While thermolysis of (132) (R H) gives 1,2,4-oxadiazoles (134) via azides (133) almost quantitatively, compounds (131) decompose to mixtures of products (Scheme 59) <87BSB675>. 

A similar transformation occurs during the thermolysis of l-thiacarbamyl-5-phenyl tetrazole (286) to give 5-amino-3-phenyl-1,2,4-thiadiazole (287) (Equation (43)) <92JPR283>. 

The 500°C thermolysis of the tetrazole 322 gave 9-cyanocarbazole (10%) and a good yield (60%) of 4-cyanocarbazole the process is thought to proceed via diradical 323 and nitrene 324 to explain the formation of 9-cyanocarbazole and via 325 to rationalize the minor product. ... 

A well-known reaction of tetrazoles is the thermolysis of 2,5-disubstituted tetrazoles to give nitrilimines by loss of N2 an example is shown in Scheme 4. The reaction is used not only for its synthetic potential but also as a source of nitrilimines for direct observation and exploration of their behavior. The first direct detection of a thermally generated nitrilimine was the species (31) produced by flash vacuum pyrolysis of 5-phenyl-2-trimethylsilyltetrazole (85AG(E)56). The parent nitrilimine, HCNNH, has been generated by file photolysis of tetrazole (96LA1041). 

The 1,7-electrocyclization of nitrile imines with an a,13 C=N bond 51 has also been observed by Boyd and co-workers [87JCS(CC)99], Thermolysis of the tetrazoles 49 led to an initial migration of the imidoyl group. Loss of nitrogen from tetrazole 50, followed by 1,7-electrocyclization and a [1,5]-hydrogen shift, gave the 1,3,4-benzotriazepines 52 (Scheme 17). 

The main difference in the thermolysis of tetrazolinones (44) and tetrazolinethiones (45) is the generation of sulfur (S2) and hydrogen sulfide from the latter compounds. The sulfur atom is split off from the starting molecules and not from a thermolysis product such as an isothiocyanate in a secondary reaction. The sulfurless tetrazole is then cleaved by cycloreversion, affording the corresponding isonitrile as a product that cannot be explained otherwise. There is little in common between photolysis and thermolysis of... 

Gas-phase thermolysis of 5-methyl- and 5-phenyl-2-(trimethylsilyl)-tetrazole (47) has been studied by real-time PE spectroscopy by Bock et al. (87TL617). N2 is split off quantitatively at the spectroscopically optimized temperatures of 750 K (R = CH3) and 770 K (R = C6H5), and the substituted nitrile imines are generated exclusively. 

Gas-phase thermolysis of substituted tetrazoles (46a,b and 48), the 1,4-disubstituted 1,4-dihydro-5//-tetrazol-5-oncs (49a-f) and the 1,4-disubstituted 1,4-dihydro-5/7-tetrazol-5-thiones (50b,c,e-h) have been monitored by photoelectron spectroscopy.27... 

Thermolysis of the undiluted tetrazole is violent, but controlled if dispersed in sand or... 

The results of a study of the flash vacuum thermolysis (FVT) of 2-(5-tetrazolyl)quinoline and l-(5-tetrazolyl)iso-quinoline 176 have been summarized <2004JOC2033>. By various methods, in particular, by 13C labeling experiment with l-(5-tetrazolyl-5 13C) isoquinoline 176, the tetrazole ring was shown to lose two nitrogen molecules under FVT conditions furnishing carbene 177. Carbene 177 at 400 °C affords 2-aminonaphthalene 179 and other compounds (not shown in the scheme) expected from 2-naphthylnitrene 178 (Scheme 12) <2004JOC2033>. 

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