2//-12,4-Triazepine, structure

Syntheses of several annulated 1,2,3-triazepine structures have been reported recently <2000EJC421>. Compound 7 (m.p. 245 °C, 68% yield) was obtained by reaction of benzoxazinone 6 with hydrazine hydrate in boiling ethanol (Scheme 1). The stmcture was confirmed by its IR u 1670 (C=0), 1620 (C=N), 3250 (NH) cm-1], 111 NMR (NMR - nuclear magnetic resonance), and combustion data. Furthermore, treatment of 6 with P2S5 in dry xylene resulted in the formation of 8. Subsequent reaction of 8 with hydrazine hydrate in boiling ethanol gave 9 in a 50% overall yield. The reported infrared (IR) data for 9 are as follows 1240 (C=S), 1640 (C=N), and 3250 (NH) cm-1. 

Some triazepinones in which one of the nitrogen atoms belongs to a fused azole moiety have been reported. For instance, compound 63 was prepared (74JHC751) and its X-ray structure determined (75CSC317). Similarly, and NMR spectra and X-ray structural determination of 64 revealed that this compound exists as a 3//-tautomer with the 1,2,4-triazepine ring in a distorted boat conformation (88T7185). 

The gas-phase basicity (GB) of 3-thio-5-oxo 1, 5-thio-3-oxo 2, and 3,5-dithio 4 derivatives of 2,7-dimethyl-[l,2,4]-triazepine (Figure 1) has been measured by means of Fourier transform ion cyclotron resonance (FTICR) mass spectrometry and complemented with theoretical calculations. The experimental FTICR results are discussed in Section 13.14.4.1.l(i). The structures and vibrational frequencies of all stable protonated tautomers and all transition states connecting them have been obtained by means of the B3LPY density functional method, together with 6-31G basis set expansion. The final energies were obtained at the B3LYP/6-311 + G(3df,-2p) level (2002JPC7383). 

In the synthesis of l,2,5-triazepine-l,5-diones, which are expected to mimic the structural features of or-peptidyl prolin-amides, the preparation of N2,N3-disubstituted derivatives 213a from the reaction of (Z)-alanine with the N2-substituted triazepines 213 resulted in lower yields. It has been reported that these fused triazepinediones could be elaborated to give constrained rir-peptidyl proline peptide mimetics of defined stereochemistry and sequence <1997J(P1)2297>. 

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