VOL’EVA et al.
1490
The presence of a redox-labile dimethylamine moiety
3,5-Di-tert-butylsalicylic acid (I). A mixture of
equimolar quantities of aldehyde VI and sodium acetate
was heated for 2.5 h at 170–180°C in a flask equipped
with an air condenser. To the cooled melt was added water
acidified with HCl, the product was extracted into ether,
the extract was dried, the solvent was evaporated, and
the residue was dried in a vacuum and recrystallized from
hexane. Yield 97%, mp 163–164°C (164–165°C [3]).
1H NMR spectrum (DMSO-d6), δ, ppm: 1.22 s (9H),
1.34 s (9H), 7.13 d (1H), 7.61 d (1H, Jμ 2.2 Hz, OH in
exchane with COOH). Mass spectrum, m/z: 250 [Μ]+.
Found, %: C 71.65; H 8.43. C15H22O3. Calculated, %:
C 72.00; H 8.75. At melting aldehyde III with sodium
acetate under similar conditions the initial aldehyde was
recovered.
is evidently an indispensable condition of such function-
alization. This statement is confirmed in particular by
comparison with the bromination results of 2,4-di-tert-
butyl-6-dimethylaminomethylphenol (XII) proceeding as
ipso-substitution and giving bromophenol VIII. No
derivatives of acid I were obtained in this process. In
studying probable intermediates we succeeded in
detecting an adduct of initial phenol XII with two
bromine molecules identified as salt XIII that possesses
limited stability and gradually converted into bromide
VIII.
OH
t-Bu
CH2N(CH3)2
Conversion of 2,4-di-tert-butyl-6-bromophenol
(VIII) under conditions of Duff reaction. In 24 ml of
ethylene glycol 0.7 g (2.4 mmol) of bromophenol VIII
[4] and 1.4 g (10 mmol) of urotropin was heated for 1 h
at 140°C. The reaction mixture was poured into water,
extracted with ether, and the solvent was evaporated.
Yield of benzoxazine VII 0.44 g (78%), mp 169–170°C
(from hexane–methanol, 10:1). From the mother liquor
was isolated 0.09 g (15%) of nitrile IX, mp 52–53°C.
1H NMR spectrum (DMSO-d6), δ, ppm: 1.33 s (9H),
1.44 s (9H), 7.27 d (1H), 7.58 d (1H, Jμ 2.4 Hz), 8.62
(OH). Mass spectrum: m/z 231 [Μ]+. In the sample of
nitrile IX was detected the presence of amide X, m/z
249 [Μ]+. By TLC acid I was also detected in the mother
liquor.
t-Bu
XII
O
+
t-Bu
CH2NH(CH3)2
2 Br2
Δ
_
VIII
Br3
Br
XIII
t-Bu
EXPERIMENTAL
1H NMR spectra were registered on a spectrometer
WH-250 (250 MHz), internal reference TMS. Mass
spectra were measured on a Hitachi Μ-80 A instrument
(electron impact, 70 eV). TLC analysis of the reaction
mixtures was carried out on Silufol UV-254 plates.
2,4-Di-tert-butyl-6-{[6,8-di-tert-butyl-2H-1,3-
benzoxazin-3(4H)-yl]carbonyl}phenol (XI). To 0.46 g
(1 mmol) of benzoxazine VII in hexane was added
dropwise at stirring 0.3 ml of Br2. The reaction mixture
was diluted with ether and washed with water. On
evaporating the solvent the residue was crystallized from
a mixture hexane–methanol, 10:1. We obtained 0.3 g
(67%) of amide X, mp 190–191°C. 1H NMR spectrum
(DMSO-d6), δ, ppm: 1.24 s (9H), 1.29 s (9H), 1.35 s
(9H), 1.37 s (9H), 4.64 s (2H), 5.43 s (2H), 7.18 d (1H),
3,5-Di-tert-butylacetylsalicylic aldehyde (VI). To
0.47 g (2 mmol) of aldehyde III and 0.31 g (3 mmol) of
acetic anhydride was added 0.2 g (2 mmol) of freshly
calcined sodium acetate and 2 ml of anhydrous pyridine.
The reaction mixture was heated on an oil bath at 160–
170°C for 5 h, then it was treated with water acidified
with HCl. The formed oily substance was extracted into
ether, the extract was dried with Na2SO4, the solvent was
evaporated, and the residue of the reaction product was
recrystallized from hexane. Yield 0.52 g (93%), mp 88–
89°C. 1H NMR spectrum (CDCl3), δ, ppm: 1.36 s (9H),
1.39 s (9H), 2.42 s (3H), 7.68 d (1H), 7.70 d (1H,
Jμ 2.4 Hz), 9.91 C (1H). Found, %: C 73.65; H 8.54.
C17H24O3. Calculated, %: C 73.80; H 8.75.
1
7.20 d (1H), 7.49 d (1H), 7.69 d (1H, Jμ ≈ Jμ 2.2 Hz),
9.13 (OH). 13C (DMSO-d6), δ, ppm: 25.66, 29.85, 31.19,
31.51 (CH3, t-Bu), 33.92, 34.29, 34.57, 34.80 (Cquat
,
t-Bu), 44.88 (NCH2), 77.69 (OCH2), 122.07, 123.36,
124.80, 128.59 (CHAr), 118.326, 123.55, 137.01, 137.34,
141.45, 144.51, 151.68, 154.55 (CAr), 163.76 (C=O).
Mass spectrum: m/z 479 [Μ]+. Found, %: C 77.39; H 9.51.
C31H45NO3. Calculated, %: C 77.61; H 9.69.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 43 No. 10 2007