TRIAZININES - SYNTHESIS AND PROTEOLYTIC DECOMPOSITION OF A NEW CLASS OF CYCLIC TRIAZENES

The reaction of 1-azido-3-chloropropane with various Grignard reagents and subsequent treatment with anhydrous isopropylamine results in the formation of the corresponding azimine. If the initial magnesium-tria zene complex is first hydrolyzed with Dowex resin and then concentrate d, the resultant linear triazene begins self-catalyzed cyclization to form the six-membered-ring triazenes as the major product, with HCl as the byproduct. Addition of an amine, at reduced temperature, allows f or the neutralization of the byproduct, HCl, which would otherwise rea ct with the linear triazene and the cyclic six-membered-ring triazene to form hydrolysis products. We have assigned the trivial name of tria zinines to this new class of cyclic triazenes. The hydrolytic decompos ition of these compounds in mixed acetonitrile-aqueous buffers predomi nantly forms 3-(alkylamino)-1-propanol and lesser amounts of the rearr anged alcohol 1-(alkylamino)-2-propanol and N-alkyl-2-propenamine. The rate of hydrolysis of 1-alkyltriazinines is approximately equal to th at of the analogous 1,3,3-trialkyltriazenes, about three times slower than that of the analogous 1-alkyltriazolines, and varies in the order ethyl > butyl > 3,3-diethoxypropyl > benzyl, As was true for other tr iazenes, the mechanism of the decomposition was found to be specific a cid-catalyzed (Al), involving rapid reversible protonation followed by rate-limiting formation of a 3-(alkylamino)propyldiazonium ion. The s lopes of the log k(obs) versus pH plots were near -1.0. The solvent de uterium isotope effect, k(H2O)/k(D2O), was in all cases <1.0 and range s from 0.82 for 1-benzyltriazinine to 0.89 for 1-ethyltriazinine. The activation parameters of the proteolytic decomposition of a series, 1- ethyltriazinine, 1-ethyltriazoline, 1,3,3-triethyltriazene, and 1-ethy l-3-methyltriazene, had similar values for Delta H-double dagger (+9 - -> 12 kcal/mol) and Delta S-double dagger (+7 --> 15 eu), respectively .