5-(a-Diazoethyl)tetrazoles, Methyl Tetrazol-5-yl Ketone Hydrazones, Silver(I) Oxide, D ehydrogenationHydrazone dehydrogenation with silver(I) ox ide in the presence of sodium hydroxide was found an efficient approach to the title com pounds, whereas application of the Bamford-Stevens reaction proved unsatisfactory.In connection with rearrangem ent studies in the 1,2,3-triazole series [1] we needed authentic sam ples of certain 5-(a-diazoethyl)tetrazoles, viz. 1 and 5 and the anion of 9. While detailed knowl edge is available for preparing a wide variety of diazoalkanes [2], experience in making tetrazolylsubstituted types is limited. Known routes starting from tetrazoles as substrates include (/) diazo transfer [3] and -for (diazower/zyOtetrazolesfunctional group transform ation such as (ii) amine diazotization in weakly acidic media [4], (Hi) the Bamford-Stevens reaction [1,4] and (iv) alkaline cleavage of N-alkyl-N-nitrosourethanes [4,5]. A p plication of m ethod i requires either an additional activating substituent (usually an acyl group) or an enamine function, m ethod ii should be ineffectual with 5 and 9, and m ethod iv requires an elaborate educt synthesis. We therefore attem pted the short approach iii.The requisite ketones 2, 6 and 10 (precursors to the tosylhydrazones 3, 7 and 11) are readily avail able. As for 2 (a still unknown tetrazole), the straightforward sequence 13 -* 14 -» • 15 -* 2 based on standard procedures [6] was used. The isomer 6 could easily be made from the nitrile 17 (obtain able as m ajor product by methylation of 16 [7]). This route was given preference over a literature m ethod that starts from the carboxylic ester (17: C 0 2Et in place of CN) [8], because in that case * Reprint requests to Prof. Dr. D. Moderhack. the educt (likewise made via ring methylation) was later shown to consist of an inseparable 1:1 mix ture of 1-and 2-methyl isomers [7,9] and, hence, has been used impure [8], For the ketone 10, an expedient synthesis (akin to that shown for 6) has lately been published [10].When the tosylhydrazone 3 was treated in the m anner described for the analogous aldehyde de rivative [4], only traces of the desired diazo com pound 1 (if any) were formed, although for this reaction the more favourable (£')-isomer of 3 was employed [11], In the case of 11, the variant that earlier proved effective with the ring-unsubsti tuted aldehyde congener [1] was tried [i.e., brief heating (< 5 min) with DBN ( 1,5-diazabicyclo-[4.3.0]non-5-ene) in DMSO as solvent], but here too our efforts remained unrewarded. Since under these conditions also both 3 and 7 [the latter avail able in (Z)-form only] turned out to be unsuitable candidates, we converted the above ketones into the hydrazones 4, 8 and 12 [12], When these deriv atives were treated with silver(I) oxide in the pres ence of sodium hydroxide, a smooth reaction oc curred to produce the expected m aterials 1, 5 and 9 in reasonable yield. We found that for a success ful transform ation 12 -* 9 the sodium salt of 12 is required (rather than...

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5-Tetrazolecarbonitrile, Grignard Reaction, 5-Acetyltetrazole 5-Acetyltetrazole can be obtained in 75% yield by reacting 5-tetrazolecarbonitrile (the latter available by an efficient literature procedure) with an excess o f methylmagnesium iodide.

The scope of the title process has been studied, showing that anions 4Ј having R ‫؍‬ H, (substituted) Ph and CO 2 Me react cleanly (and still satisfactorily in the case R ‫؍‬ Me), while with R ‫؍‬ COMe, COAr and CN extensive decomposition occurs. The experimental findings (rate constants, activation parameters) have been elucidated through PM3 calculations.

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