O. Yu. Smirnov

Nucleophilic substitution in benzo-1,2,3,4-tetrazine 1,3-dioxides

Nucleophilic substitution in nitro- and bromobenzo-1,2,3,4-tetrazine 1,3-dioxides (BTDOs) was studied. In most cases, the bromo and nitro groups are replaced by methylamino, dimethylamino, azido, and methoxy groups without opening of the tetrazine ring. It was illustrated with the reactions of dibromo-BTDOs with sodium methoxide that the reactivity of positions 5 to 8 in their benzene ring as regards nucleophilic substitution changes in the following order: 6 > 8 > 7 > 5. The structures of the BTDOs obtained were confirmed by 1H, 13C, and 14N NMR data.

Annulated benzotetrazine 1,3-dioxides 2.* [1,2,5]Oxadiazolo[3,4-f ][1,2,3,4]benzotetrazine 1,3,7-trioxide

Thermolysis of 8-azido-7-nitrobenzotetrazine 1,3-dioxide led to benzotetrazine 1,3-dioxide annulated with the furoxan ring at the C(7)—C(8) bond. Complete assignment of the signals in the 13C NMR spectrum of the compound obtained was performed. Attempted syntheses of benzotetrazine 1,3-dioxides annulated with a furoxan ring at the C(6)—C(7) bond or two furoxan rings at the C(5)—C(6) and C(7)—C(8) bonds were unsuccessful.

Nitration and bromination of benzo-1,2,3,4-tetrazine 1,3-dioxides

Benzo-1,2,3,4-tetrazine 1,3-dioxide (BTDO) and its derivatives were nitrated with HNO3/H2SO4 or HNO3/oleum and brominated with dibromoisocyanuric acid in CF3CO2H/H2SO4 (5 : 1) or H2SO4. The reactivity of positions in the benzene ring of this heterocyclic system as regards electrophilic substitution was found to change in the following order: 5 ≈ 7 > 8 > 6. Mono- and dinitro-BTDOs and mono- and polybromo-BTDOs were synthesized. Their structures were confirmed by 1H, 13C, and 14N NMR spectra.

Annulated benzotetrazine 1,3-dioxides 1. [1,2,5]Oxadiazolo[3,4-f][1,2,3,4]benzotetrazine 2,4,7-and 2,4,9-trioxides

Thermolysis of 6-azido-5-nitro-7-R-benzotetrazine 1,3-dioxides (R = H and Br) gave benzotetrazine 1,3-dioxides annulated with the furoxan ring at the C(5)-C(6) bond. According to the NMR data, these compounds at 297 K are equilibrium mixtures of two isomers with different positions of the N-oxide oxygen atom in the furoxan ring. Full assignment of signals in the 13C NMR spectra of the compounds obtained was accomplished.

First example of the formation of bipolar spiro σ-complexes from 6-bromo-5,7-dinitrobenzo[e]-1,2,3,4-tetrazine 1,3-di-N-oxide

The reactions of 3,5,7-trimethyltropolone and 2-(N-benzylamino)tropone with 6-bromo-5,7-dinitrobenzo[e]-1,2,3,4-tetrazine 1,3-di-N-oxide afforded novel bipolar spiro σ-complexes. The kinetic and activation parameters of the R,S-enantiotopomerization of a chiral spiro σ-complex of 2-(N-benzylamino)tropone were determined using dynamic 1H NMR spectroscopy.

Synthesis of brominated 2-(tert-butyl-NNO-azoxy)anilmes

Abstract2-(tert-Butyl-NNO-azoxy)aniline was prepared by selective reduction of 2-(tert-butyl-NNO-azoxy)nitrobenzene. Its bromination yielded the correspondingpara-bromo- andortho, para-dibromoanilines (3a,b).meta-Bromoanilines (6a,b) were synthesized by selective replacement of theortho-bromine atoms in ortho,para-bromo(tert-butylazoxy)benzenes (5a,b) by ammonia in toluene under pressure.

Syntheis of amino-substituted 1,3-bis(tert-butyl-NNO-azoxy)benzenes

Oxidation of 4,6-dichloro-1,3-phenylenediamine with Caros acid yields the corresponding dinitrosobenzene, which reacts withN,N-dibromo-tert-butylamine to give 1,5-bis(tert-butyl-NNO-azoxy)-2,4-dichlorobenzene. Treatment of the latter with ammonia yields 4-amino-and 4,6-diamino-1,3-bis(tert-butyl-NNO-azoxy)benzenes.

Synthesis and tautomeric transformations of 2 -(tert-butyl ) -1,2,4 -benzotriazine -3 (2H ) -thiones

Treatment of 2-(tert-butyl)-1,2,3,4-benzotetrazinium tetrafluoroborates with sodium thiocyanate afforded 2-(tert-butylazo)phenyl isothiocyanates 3, which exist in equilibrium with 2-(tert-butyl)-1,2,4-benzotriazine-3(2H)-thiones 3′. The equilibrium depends on the substituents R in the benzene ring: the percentage of the open isomer 3 is about 20% for R = H or Me; for R = Cl or Br, the equilibrium is completely shifted to cyclic isomer 3′. The equilibrium is slow on the time scale of the 1H and 13C NMR experiments. For compounds 3a/3′a (R = H), the spectra at 24 °C show two sets of signals, while those at 0 °C contain only signals for isomer 3′a.