A comparison of 13C spectra for a series of substituted 5-phenyltetrazoles, (RC,H,; R = H,p-Me, p-NO,. o-NO,), with their I-Nand 2-N-methyl derivatives suggested that the tetrazoles exist predominantly in the l -H form. Both l H and 13C n.m.r. spectra suggested the presence of interannular conjugation in 5-aryl-2-methyltetrazoles and 5-aryl-1 H-tetrazoles. This w a s either reduced or absent in 5-aryl-I -methyltetrazoles and also in 5-(o-nitrophenyl) -1 H-tetrazole.THE tetrazole 5-C chemical shift differs significantly in 1,5-and 2,5-disubstituted tetrazoles,1y2 and this difference is general for a wide range of 5-s~bstituents.~ Comparisons of tetrazole 5-C shifts with those of l-N-methyl (I; R' = Me) and 2-N-methyl (11; R' = Me) isomers therefore can be used to monitor tetrazole annular t a ~t o r n e r i s r n . ~~~ This approach requires the assumption that the 5-C shift is independent of exocyclic ( I bonds

Two N-methyl derivatives of a novel bicyclic system with 1 O x electrons derived from 3a-azapentalene, s-triazolo-[2,3-d]tetrazole, have been synthesized and their structures established by comparison with known isomeric systems using l H and 13C n.m.r., i.r., and mass spectra. lsomerization of the anion of azido-s-triazole to the anion of s-triazolo[2,3-d]tetrazole is confirmed.IN previous papers we showed that the azidoazomethinetetrazole equilibrium was shifted completely to the azidoform in neutral molecules of several 3-azidopyrazoles 2 and 2-a~idoimidazole,~ and to the tetrazole form in the corresponding anions. Herein we report the more complex case of azido-s-triazoles, RESULTS AND DISCUSSION 1.r. and n.m.r. spectra of 3-azido-s-triazoles (3) showed only the azido-form in solution in agreement with the l i t e r a t~r e .~,~ In the basic medium, sodium prepared unequivocally by one of us by cyclisation of t e t razol-5-yl h ydrazon yl bromides.Results for methylation of the species (l), (3), and (5)- (7), are in Table 1. Alkylations of amino-striazoles gave different results when affected on the neutral molecule and the anion.' The 4-N-alkyl isomer (2c) was particularly difficult to obtain since it was only formed in appreciable proportions in the methylation of the neutral molecule and the overall reaction yield was poor in this case. Similar results were obtained for the azido-s-triazoles. When compound (3) was methylated TABLE 1 Reagent, conditions CH,I CH,I CH,I-NaOH CH,I-NaH-DMSO NaNO, NaN, LiAlH, Li AlH, Overall product 30 70 80 95 40 46 65 yield (%I

13C nmr alkyl shifts of N-alkyl tetrazoles and azoles follow the pattern of proton shifts. The shielding of the N-alkyl group increases for the structural units[Formula: see text]The carbon spectra are more reliable for structural assignment. Syntheses of a number of mono- and dibenzyl derivatives of benzaldehyde tetrazol-5-ylhydrazone are reported.

Methylierung des Aminotriazols (I) unter Bedingungen, wie sie bereits für das Analoge (I) (R: ‐H) beschrieben worden sind, gibt die Produkte (II)‐(IV).

Der Vergleich der NMR‐Spektren der vier 5‐Aryl‐tetrazole (I)/(II) mit denen der entsprechenden 1‐ (III) und 2‐Methyl‐5‐aryltetrazole (IV) ergibt, daß die 5‐Aryl‐tetrazole bevorzugt in der l‐H‐Form (I) vorliegen.