Isomere n-aryltetrazole—IV

The mechanism of cyclization of 1,4-diaryl-1-azido-2,3-diazabuta-1,3-dienes to tetrazoles. Imidoyl azides stabilized by slow nitrogen inversion

“…The required azides (9) were prepared by the general route shown in Scheme 1. Chlorination of the hydrazide (8) by thionyl chloride gave the monochlorides (11) in good yield even when the group X was activating (e.g.…”

“…On heating in inert solvents the azides (9) were smoothly converted to the corresponding tetrazoles. On cyclization the characteristic azide absorption a t 2 100 cm-l disappeared and the U.V.…”

1,3- and 1,4-Substituted tetrazolium salts

“…Thus quaternization of 1-mono-and 1,5-disubstituted tetrazoles 4 yields a mixture of isomeric tetrazolium salts 2 and 3. 13, 15 ± 25, 27, 28, 31, 32 ± 37 In the case of 1-monosubstituted tetrazoles 4 (R 1 = H), the predominant reaction is the attack at the N(4) atom 13,15,18,21,28,33 manifesting the highest basicity (proton affinity) irrespective of the nature of the R 2 substituent. 6,8,40 The presence of a substitutent at C(5) increases the content of the 1,3substituted tetrazolium salt 2 which becomes predominant in the presence of bulky substituents R 1 .…”

Ring Transformations in Tetrazole Chemistry

“…Attempts to bring about an analogous transformation with a 4-benzoyltetrazoloquinoline failed [94]. Cyclization of 2-nitrobenzonitrile imines to 2,l -benzisoxazoleN-oxides is not observed if the dipole bears an acyl or azin-2-yl substituent at the nitrogen atom [95] (cf. Section 3.4 on 4H-1,2,4-triazoles and 1,3,4-0xadiazoles).…”

“…Converting the amino group of the tetrazolopyrimidine 142 (X = N, R' = NH2, R2 = H) into an imidate function at elevated temperature leads directly to the fused imidazole 145 [124]. Pyrolysis of 2H-tetrazoles 157 that have a 2,4-dinitrophenyl [ 1301 or a substituted 5-nitropyrimidin-4-y1 ligand [95] at N(2) gives high yields of the triazole derivatives 158; ring contraction of the 1,2,5,6-0xatriazepine unit is followed by an N+O acyl shift. For the behaviour of the 1H-isomer of 157, see this Section on 2H-1,2,3-triazoles.…”