2-(4-(Dimethylamino)phenyl)-3,3-difluoro-4,6-diphenyl-3,4-dihydro-1,2,4,5,3-tetrazaborinin-2-ium-3-ide

: Reaction of 1-(4-(dimethylamino)phenyl)-3,5-diphenylformazane with boron triﬂuoride diethyl etherate (5 equiv) in the presence of triethylamine (3 equiv) in toluene medium gave “boratetrazine”— 2-(4-(dimethylamino)phenyl)-3,3-difluoro-4,6-diphenyl-3,4-dihydro -1,2,4,5,3-tetrazaborinin-2-ium-3-ide in a 58% yield. Abstract: Reaction of 1-(4-(dimethylamino)phenyl)-3,5-diphenylformazane with boron trifluoride diethyl etherate (5 equiv) in the presence of triethylamine (3 equiv) in toluene medium gave “bo-ratetrazine”—2-(4-(dimethylamino)phenyl)-3,3-difluoro-4,6-diphenyl-3,4-dihydro -1,2,4,5,3-tetrazaborinin-2-ium-3-ide in a 58% yield.

The reaction between boron trilfuoride etherate and more complex substrates con taining additional groups, which can coordinate to the boron, proceeds nontrivially, as in the case of 11-14 (Figure 2), where coordination is realized through the oxygen atom [30][31][32][33]. To date, only one representative of "boratetrazines" having a dono N,N-dialkylamino group has been described [34]. It was prepared from cyanoformazan containing the 4-(dimethylamino)phenyl fragment in the N 1 and N 5 positions. The aim o the present work was to study the reaction of triarylformazan containing the N,N-dialkylamino group in the N 1 position with boron trifluoride etherate.
The reaction between boron trilfuoride etherate and more complex substrates containing additional groups, which can coordinate to the boron, proceeds nontrivially, as in the case of 11-14 ( Figure 2), where coordination is realized through the oxygen atom [30][31][32][33]. To date, only one representative of "boratetrazines" having a donor N,N-dialkylamino group has been described [34]. It was prepared from cyanoformazan containing the 4-(dimethylamino)phenyl fragment in the N 1 and N 5 positions. The aim of the present work was to study the reaction of triarylformazan containing the N,N-dialkylamino group in the N 1 position with boron trifluoride etherate.

Results and Discussion
To begin, 1-(4-(dimethylamino)phenyl)-3,5-diphenylformazan 17 was synthesized from phenylhydrazone benzaldehyde 15 [35] and diazotized N,N-dimethyl-p-phenylenediamine in a pyridine medium (Scheme 2). The target formazane 17 was purified by flash chromatography and recrystallization from ethanol. Its physical constants and spectral data are in agreement with the literature data [36]. To date, only one representative of "boratetrazines" having a donor N,N-dialkylamino group has been described [34]. It was prepared from cyanoformazan containing the 4-(dimethylamino)phenyl fragment in the N 1 and N 5 positions. The aim of the present work was to study the reaction of triarylformazan containing the N,N-dialkylamino group in the N 1 position with boron trifluoride etherate.
The reaction between boron trilfuoride etherate and more complex substrates containing additional groups, which can coordinate to the boron, proceeds nontrivially, as in the case of 11-14 ( Figure 2), where coordination is realized through the oxygen atom [30][31][32][33]. To date, only one representative of "boratetrazines" having a donor N,N-dialkylamino group has been described [34]. It was prepared from cyanoformazan containing the 4-(dimethylamino)phenyl fragment in the N 1 and N 5 positions. The aim of the present work was to study the reaction of triarylformazan containing the N,N-dialkylamino group in the N 1 position with boron trifluoride etherate.

Results and Discussion
To begin, 1-(4-(dimethylamino)phenyl)-3,5-diphenylformazan 17 was synthesized from phenylhydrazone benzaldehyde 15 [35] and diazotized N,N-dimethyl-p-phenylenediamine in a pyridine medium (Scheme 2). The target formazane 17 was purified by flash chromatography and recrystallization from ethanol. Its physical constants and spectral data are in agreement with the literature data [36]. The reaction of 1-(4-(dimethylamino)phenyl)-3,5-diphenylformazan 17 with fivefold excess boron trifluoride diethyl etherate was performed in the presence of threefold excess triethylamine in toluene medium. Monitoring of the reaction by analytical thin-layer chromatography (TLC) showed that complete conversion was achieved after 5 h of stirring the reaction mixture at 90 °C (Scheme 3). After flash chromatography and recrystallization from ethanol, the yield of target "boratetrazine" 18 was 58%.

Materials and Methods
The reactions were monitored by thin-layer chromatography (Sorbfil, Imid Ltd., Krasnodar, Russia). The 1 H-NMR, 13 C-NMR, 11 B-NMR and 19 F-NMR spectra were acquired on ECA400 (JEOL) (400 and 100 MHz, respectively) spectrometers in CDCl3 at room temperature. The chemical shifts δ were measured in ppm with reference to the residual solvent resonances ( 1 H: CDCl3, δ = 7.25 ppm; 13 C: CDCl3, δ = 77.2 ppm). The splitting patterns are referred to as s, singlet; d, doublet; t, triplet; m, multiplet. Coupling constants (J) are given in hertz. IR spectra were recorded on an IR Prestige (Shimadzu, Kyoto, Japan), using tablets of samples with KBr. High-resolution and accurate mass After flash chromatography and recrystallization from ethanol, the yield of target "boratetrazine" 18 was 58%.

Materials and Methods
The reactions were monitored by thin-layer chromatography (Sorbfil, Imid Ltd., Krasnodar, Russia). The 1 H-NMR, 13 C-NMR, 11 B-NMR and 19 F-NMR spectra were acquired on ECA400 (JEOL) (400 and 100 MHz, respectively) spectrometers in CDCl3 at room temperature. The chemical shifts δ were measured in ppm with reference to the residual solvent resonances ( 1 H: CDCl3, δ = 7.25 ppm; 13 C: CDCl3, δ = 77.2 ppm). The splitting patterns are referred to as s, singlet; d, doublet; t, triplet; m, multiplet. Coupling constants (J) are given in hertz. IR spectra were recorded on an IR Prestige (Shimadzu, Kyoto, Japan), using tablets of samples with KBr. High-resolution and accurate mass In conclusion, it was shown that the reaction of triarylformazane with a donor dimethylamino group 17 with boron trifluoride etherate leads to the formation of "boratetetrazine" 18. The notion that the coordination of boron occurs only due to the azohydrazone fragment was confirmed.
3.1. 1-(4-(Dimethylamino)phenyl)-3,5-diphenylformazan (17) Diazonium salt solution (obtained from 3.52 g (0.0168 mol) N,N-dimethyl-p-phenylenediamine dihydrochloride, 1.16 g NaNO 2 and 4 mL conc. HCl in 30 mL water) was added to a solution of 3 g (0.0153 mol) of phenylhydrazone benzaldehyde in 100 mL pyridine at −5 • C. Then, a solution of 2.5 g NaOH in 6 mL water was added and stirred at −5 • C for 1 h. Then, the temperature was raised to 15 • C and the reaction mixture was allowed to stand for 6 h. The reaction mixture was poured into 500 mL of cooled 2M HCl; the resulting brown precipitate was filtered off, washed on a filter with water and dried in the desiccator. It was purified by flash chromatography on alumina (neutral) eluting with a hexanedichloromethane mixture (10:1) and subsequent recrystallization from ethanol.  Figure S2). 13 Figure S4).