REACTION OF α-BROMOCARBOXYLIC ACIDS WITH HYDRAZINE
2167
stitution with hydrazine hydrate allowed us to expect that
dimethylhydrazine can also be involved in this process.
The latter compound is known possessing highr
enucleophilicity and basicity as compared with the
unsubstituted hydrazine, and this should promote
bromine substitution in the α-bromocarboxylic acids and
should lead to practically unstudied α-dimethylhy-
drazinocarboxylic acids. We studied reaction of dimethyl-
hydrazine with compounds Ia–d. As might be expected,
dimethylhydrazine reacts with compounds Ia–d in
absolute alcohol or acetonitrile medium smoothly. Small
excess of dimethylhydrazine (1.05 to 1.1 mol per 1 mol
of α-bromocarboxylic acid) was used and reaction was
carried out at 40–60ºC during 5–10 h leading to formation
of N-(1-carboxyalkyl)-N,N-hydrazinium bromides IIIa–
c in 60–70% yield according to equation:
It is noteworthy that the compounds obtained are
hygroscopic ones and require use of absolute solvents
both in the steps of synthesis and recrystallization.
Nature of the obtained compounds is confirmed by
the data of IR and 1H NMR spectroscopy (Table 5) and
the data of elemental analysis (Table 6). Presence in the
IR spectra of characteristic absorption bands in the region
of 3220–3240 cm–1characteristic adsorption attests
presence of protonated NH+3 group and points probably
to zwitter-ionic structure of α-dimethylhydrazinocarb-
oxylic acids. This also is confirmed by 1H NMR spectra
where occur signals (multiplet) in the range 3.1–3.5 ppm
depending on substituent R (500 MHz, DMSO-d6) of
α-methine fragment; presence of clearly defined signal
at 5.6 ppm (4H) and absence of signals of OH and NH2
groups points probably to zwitter-ionic structure of the
compounds.
Like with hydrazinocarboxylic acids, the
dimethylhydrazinium salts are characterized by signal
of methine group at 3.05–4.3 ppm (multiplet), by signal
of methyl groups at 3.5–3.6 ppm (singlet), while the
signal at 5.35–5.67 ppm (singlet) is probably in
correspondence with the existence of compounds IIIa–
d as internal salts.
EXPERIMENTAL
where R is Me (a), Et (b), i-Pr (c) and Ph (d).
1H NMR spectra are registered on a Bruker AM 500
spectrometer (internal reference TMS) in DMSO-d6. IR
spectra are obtained on a IKS-29 spectrmeter from the
pastes with Vaseline oil.
The data on the synthesis conditions of hydrazonium
salts IIIa–d are comprised in Table 4.
Isolation of the reaction products included concentrat-
ing the reaction solutions under vacuum, cooling from
–5 to –10ºC, filtrating the crystals formed and recrystal-
lizing them from 2:1 isopropyl alcohol–dioxane mixture.
General procedure for preparation of α-hy-
drazinocarboxylic acids IIa–Id. To a three-necks flask
equipped with mechanical stirrer, reflux condenser and
Table 5. Spectral characteristics of compounds IIIa–d
No.
1
Compound
IR spectrum, cm–1
1H NMR spectrum, δ, ppm (DMSO-d6)
1.55 d (3H, CH3); 3.15 q (1H, CH); 3.52 s (6H, 2CH3), 5.36 s
(3H, NH2, OH)
+
IIIa
3220 (NH3 ); 1610 (C= O)
0.94 t (3H, CH3); 2.2 m (2H, CH2); 3.05 q (1H, CH); 3.52 d
(6H, 2CH3), 5.4 s (3H, NH2, OH)
+
2
3
4
IIIb
IIIc
IIId
3250 (NH3 ); 1590 (C=O)
0.91 d (3H, CH3); 0.94 d (3H, CH3); 2.98 m (1H, CH); 3.6 d
(6H, 2CH3), 4.28 m (1H, CH); 5.66 s (3H, NH2, OH)
+
3300 NH3 ); 1595 (C=O)
3.58 d (6H, 2CH3), 4.12 C (1H, CH); 5.67 s (3H, NH2,OH);
+
3320 (NH3 ); 1620 (C=O)
7.64–8.03 (5Harom
)
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 12 2007