Russian Journal of General Chemistry, Vol. 71, No. 5, 2001, pp. 817-818. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 5, 2001,
pp. 870 871.
Original Russian Text Copyright
2001 by Kuznetsov, Brusilovskii, Mazepa.
LETTERS
TO THE EDITOR
Reaction of 2-Isopropyl-5,6-benzo-1,3,2-oxazaborepane
with Acetonitrile
V. V. Kuznetsov, Yu. E. Brusilovskii, and A. V. Mazepa
Bogastskii Physicochemical Institute, National Academy of Sciences of Ukraine, Odessa, Ukraine
Ufa State Petroleum Technical University, Ufa, Bashkortostan, Russia
Received July 10, 2000
Reaction of substituted 1,3,2-dioxaborinanes with
acetonitrile yields the corresponding 2-methyl-5,6-
dihydro(4H)-1,3-oxazines [1, 2]. Under the same con-
ditions 2-isobutyl-4,6,6-trimethyl-1,3,2-oxazaborinane
converts to 2,4,6,6-tetramethyl-1,4,5,6-tetrahydropy-
rimidine [3]. Here, with 2-isopropyl-5,6-benzo-1,3,2-
oxazaborepane I as example, we showed for the first
time that seven-membered cyclic borates of amino al-
cohols can undergo a similar transformation to give
1,2-diaminomethylbenzene III, the product of hydrol-
ysis of the intermediate 2-methyl-3,4-dihydro-1,3-ben-
zodiazepine II.
-
-
O
NH
C CH3
N
NH2
NH2
CH3CN, H+
OH
B i-C3H7
NH
I
-
-
II
III
Compound II was not isolated, apparently because
of its high tendency to hydrolysis. Diamine III was
obtained in a 65% yield as a dark red oil with a char-
acteristic odor. Its composition and structure were con-
cyclic esters of boric acid [5]; it is a fairly convenient
route to the corresponding 1,4-diamines.
The initial cyclic boronic ester I was prepared by
the reaction of 1-hydroxymethyl-2-aminomethylben-
zene [6] with dibutyl isopropylboronate, following the
1
firmed by H NMR and IR spectroscopy and mass
spectrometry. The 1H NMR spectrum contains the char-
acteristic signals of all the groups of protons, , ppm:
1.15 s (4H, NH2), 3.49 s (4H, CH2 N), and 6.99 s
general procedure [2], as a dark red oil in a 53% yield.
1
IR spectrum, , cm : 3150 ( NH), 1600 (
).
CCarom
1H NMR spectrum, , ppm: 0.90 d (6H), 1.42 m (1H),
3.09 s (1H), 3.53 s (2H), 3.71 s (2H), 7.21 s (4H).
Mass spectrum, m/z (Irel, %): 189 (18) [M]+, 146 (71)
[M C3H7]+, 119 (100) [M C3H7 BNH2]+. To
a solution of 0.006 mol of this compound in 100 ml of
acetonitrile, 0.2 mol of concentrated sulfuric acid was
slowly added dropwise with stirring. After that the re-
action mixture was refluxed on a water bath for 5 h,
excess acetonitrile was removed on a rotary evapora-
tor, and the viscous residue was diluted with 100 ml
of water and extracted with chloroform (2 50 ml).
The remaining aqueous phase was cooled with ice
and alkalized with solid NaOH to pH 9 10. The re-
sulting red-brown residue of an unidentified com-
pound was filtered off (yield 0.21 g), and the aque-
ous phase was extracted with chloroform (4 50 ml).
After removing the solvent, 0.53 g of diamine III was
isolated.
(4H, C6H4). The IR spectrum contains strong bands
1
at 3280 ( NH) and 1540 cm
(
). The mass
CCarom
spectrum contains a peak of an ion with m/z 119,
which is the most intense and corresponds to frag-
mentation of M + [4].
+
+
NH2
NH2
NH3
NH2
m/z 136 (<1)
m/z 119 (100)
Along with III, an unidentified crystalline red-
brown substance was isolated from the reaction mix-
ture. It decomposes on heating above 270 C; the
highest m/z value in its mass spectrum is 248 (5).
The discovered reaction evidently proceeds by the
mechanism similar to that observed for six-membered
1070-3632/01/7105-0817$25.00 2001 MAIK Nauka/Interperiodica
Kuznetsov
