Synthesis of (azidomethyl)phenylboronic acids

Article abstract of DOI:10.1023/B:RUCB.0000030813.05424.1f

The synthesis of 2-, 3-, and 4-(azidomethyl)phenylboronic acids was carried out. The geometric and electronic structures were studied by quantum-chemical methods. The suggestion is made that there are weak intramolecular interactions between the boron atom and the nitrene nitrogen atom of the azido group.

Full text of DOI:10.1023/B:RUCB.0000030813.05424.1f

370
Russian Chemical Bulletin, International Edition, Vol. 53, No. 2, pp. 370—375, February, 2004
Synthesis of (azidomethyl)phenylboronic acids
A. Yu. Fedorov,aꢀ A. A. Shchepalov,a A. V. Bol´shakov,a A. S. Shavyrin,b Yu. A. Kurskii,b
J.ꢀP. Finet,c and S. V. Zelentsova
aN. I. Lobachevsky University of Nizhnii Novgorod,
23 prosp. Gagarina, 603950 Nizhnii Novgorod, Russian Federation.
Fax: +7 (831 2) 65 8592. Eꢀmail: afnn@rambler.ru
bG. A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences,
49 ul. Tropinina, 603600 Nizhnii Novgorod, Russian Federation.
Fax: +7 (831 2) 12 7497. Eꢀmail: andrew@imoc.sinn.ru
cFaculty of Science of St. Jerome,
AixꢀMarseille University, 13397 Marseille, France.*
Fax: +33 4 91 288758. Eꢀmail: finet@srepir1.univꢀmrs.fr
The synthesis of 2ꢀ, 3ꢀ, and 4ꢀ(azidomethyl)phenylboronic acids was carried out. The
geometric and electronic structures were studied by quantumꢀchemical methods. The suggesꢀ
tion is made that there are weak intramolecular interactions between the boron atom and the
nitrene nitrogen atom of the azido group.
Key words: azidomethylphenylboronic acids, synthesis, quantumꢀchemical calculations.
Boronic acids have found wide use in fine organic
49% yields, respectively, as viscous oils by the reactions of
synthesis. For example, Suzuki crossꢀcoupling involving
arylboronic acids1—10 is one of the most convenient and
ecologically safe methods11,12 for the construction of new
C—C bonds. In the presence of copper salts as catalysts,
arylboronic acids serve as efficient Oꢀ,13,14 Nꢀ,15 and
Sꢀarylating reagents.16 Mild synthesis conditions, high
regioselectivity of these processes, the possibility of perꢀ
forming arylation of optically active substrates without
epimerization, and high yields of Nꢀ, Oꢀ, and Sꢀarylation
products favorably distinguish the reactions with arylꢀ
boronic acids from the classical Ullmann reaction.17
In the present study, we synthesized previously
unknown arylboronic acids containing the 2ꢀ, 3ꢀ, or
4ꢀazidomethylphenyl groups and investigated their strucꢀ
tures and the electron density distribution. Organic azides
are extensively used for performing various chemical transꢀ
formations.18,19 Hence, arylboronic acids, which allow
one to insert the benzylazide fragments into organic subꢀ
strates to form new C—C, C—N, C—O, and C—S bonds,
are of considerable interest.
(bromomethyl)phenylboronic acids with NaN3 in dry
DMF. Acids 3a—c were obtained as solvates with DMF.
Scheme 1
Reagents and conditions: i. NBS, (BzO)2; ii. NaN3, DMF.
1
All the derivatives synthesized were identified by H,
Radical bromination of known orthoꢀ, metaꢀ, and
paraꢀtolylboronic acids using NBS as a brominating agent
afforded 2ꢀ, 3ꢀ, and 4ꢀ(bromomethyl)phenylboronic acꢀ
ids 2a—c as polycrystalline products in 58, 37, and 39%
yields, respectively. In the next step, (azidomethyl)phenylꢀ
boronic acids 3a—c were prepared in 46, 48, and
13C, and 11B NMR, IR, and UV spectroscopy as well as
1
by elemental analysis. It should be noted that in the H
and 13C NMR spectra of some bromoꢀ and azidoꢀsubstiꢀ
tuted derivatives, the protons of the methylene groups
and aromatic rings and the corresponding carbon atoms
appear as several signals with insignificantly differꢀ
ent chemical shifts (the differences are 0.02—0.40 and
* CNRSꢀUniversites d'AixꢀMarseille 1 et 3, UMR 6517, Faculte
des Sciences de SaintꢀJerome, 13397 Marseille Cedex 20, France.
1
0.10—1.3 ppm for the H and 13C NMR spectra, reꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 356—361, February, 2004.
1066ꢀ5285/04/5302ꢀ0370 © 2004 Plenum Publishing Corporation

Synthesis of azidomethylphenylboronic acids
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
371
1
spectively). For example, in the H NMR spectrum of
precipitation with hexane from solutions in Et2O, CH2Cl2,
or CHCl3, or careful heating under reduced pressure
failed. Attempts to use azidating agents (LiN3 in THF,
Me3SiN3—SnCl4, Me3SiN3—ZnI2, Me3SiN3—ZnBr2, or
CH3C(O)N3), which enable one to insert azido groups
into organic substrates in solutions in other organic solꢀ
vents (THF, Et2O, CH2Cl2, or CHCl3),19 which are less
prone to complex formation, were unsuccessful.
(Azidomethyl)phenylboronic acids prepared in the
present study are of interest not merely from the synthetic
standpoint. The N→B donorꢀacceptor interactions in
arylboronic acids containing the electronꢀdonating nitroꢀ
gen atoms at the methyl group at position 2 of the aroꢀ
matic fragment made it possible to create a new generation
of selective fluorescence sensors for carbohydrates.24—26
In this connection, it was of interest to examine the possiꢀ
bility of coordination of the azido group to the boron
atom in 2ꢀ(azidomethyl)phenylboronic acid and study the
characteristics of the azido group in the organoboron comꢀ
pounds synthesized. To solve this problem, we used UV
spectroscopy and quantumꢀchemical methods.
The absorption spectra of 2ꢀ(azidomethyl)phenylꢀ
boronic acid 3a in different solvents are shown in Fig. 1.
The positions of the maxima in these spectra depend only
slightly on the solvent used. The absorption of the azide
chromophore at 296 nm depends on the polarity of the
solvent in a complex way. Apparently, unlike the carboꢀ
nyl and amino groups, the azido fragment cannot be effiꢀ
ciently coordinated at the boron atom. This fact is not
surprising because the boron atom is already involved in
complex formation with DMF. However, the possibility
of coordination in the absence of DMF is still an open
question.
2ꢀ(bromomethyl)phenylboronic acid in CDCl3, the sigꢀ
nals of the protons of the methylene group appear as three
singlets at δ 4.75, 5.09, and 5.15 with the intensity ratio of
3 : 3 : 14. The relative intensities of the signals characterꢀ
istic of the protons of the methylene groups as well as the
number of these signals depend substantially on the conꢀ
centration of the samples under study and the solvents
used (CDCl3, acetoneꢀd6, or DMSOꢀd6). For instance,
1
the H NMR spectra of 2ꢀ(bromomethyl)phenylboronic
acid in acetoneꢀd6 have one singlet at δ 5.00 belonging to
the protons of the methylene group. In the spectra reꢀ
corded in DMSOꢀd6, the signals of the protons of the
methylene group appear as two singlets at δ 4.93 and 5.00
with the intensity ratio of 9 : 1. It should be noted that the
chemical shifts observed in the H and 13C NMR spectra
1
belong to the methylene groups in the (monobromoꢀ
methyl)phenyl and (monoazidomethyl)phenyl fragments.
The presence of several signals in the H and 13C NMR
1
spectra cannot be attributed to the fact that the reaction
can afford not only the desired isomeric (monobromoꢀ
methyl)phenylboronic acids 2a—c but also their (dibromoꢀ
methyl)phenyl analogs.20 The dependence of the intenꢀ
sity ratio for these signals and the chemical shifts in the
1H NMR spectra on the concentration of the samples
under study as well as on the nature of the solvents used
indicates that anhydrides of boronic acids with different
degrees of oligomerization can exist along with monoꢀ
meric forms of these derivatives (ArB(OH)2) in solutions
of substituted arylboronic acids. The conclusions about
the existence of oligomeric forms of boronic acids and the
absence of byꢀproducts in the compounds isolated are
supported by the results published earlier.21
It should be noted that (azidomethyl)phenylboronic
acids were synthesized as solvates with DMF molecules.
According to the H NMR spectroscopic data for comꢀ
Quantumꢀchemical calculations of the geometric and
electronic structures of the organoboron compounds synꢀ
thesized in the present study gave an estimate of this
possibility. We carried out calculations using the density
functional theory27—29 with the B3LYP hybrid funcꢀ
tional30—32 and the 6ꢀ31G(d) basis set (B3LYP/6ꢀ31G(d))
1
pound 3a—c, there are two molecules of arylboronic acid
per DMF molecule. It is also noteworthy that the signals
for the protons of the C(O)H groups of the DMF molꢀ
ecules involved in complex formation with compounds
3a—c are observed at higher field (δ 5.93, 5.86, and 5.77,
respectively) compared to the standard chemical shift for
this fragment of the DMF molecule in CDCl3 (δ 8.02).22
This is indicative of the occurrence of rather strong doꢀ
norꢀacceptor interactions between the molecules of
arylboronic acids and DMF.23 An insignificant difference
in the 11B chemical shifts of the singlets belonging to
(azidomethyl)phenylboronic acids 3a—c and the correꢀ
sponding (bromomethyl)phenylboronic acids 2a—c as well
as broadening of these signals do not allow one to unamꢀ
biguously assign these interactions to either hydrogen
bonds or O→B coordination bonds.
logε
1
3
2
3
2
250
300
λ/nm
Attempts to remove the solvent molecules from (azidoꢀ
methyl)phenylboronic acids by repeated extraction of orꢀ
ganic solutions of derivatives 3a—c with water, repeated
Fig. 1. Electronic spectra of 2ꢀ(azidomethyl)phenylboronic acid
3a in different solvents: 1, CH2Cl2; 2, EtOH; 3, hexane.

372
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
Fedorov et al.
N
17
1.140
16
N
1.238
14
8
7
N
15
8
9
1.500
C
7
N
1.396
1.398
3
C
17
C
1.396
1.394
1.515
1.142
1
2
C
C
C
13
2
1
12
1.399
C
6
20
N
16
1.415
14
1.392
1.235
6
1.397
4
1.513
9
3
C
5
19
C
C
1.590
5
N
C
4
15
C
1.401
1.492
1.405
1.395
1.359
C
1.393
C
B
12
10
11
13
1.372
11
10
18
21
3a
4
Fig. 2. Equilibrium geometric parameters of 2ꢀ(azidomethyl)phenylboronic acid 3a and benzylazide 4 according to the results of
quantumꢀchemical calculations by the B3LYP/6ꢀ31G(d) method.
N
17
1.134
N
17
1.134
1.255
N
15
N
N
16
16
20
1.255
1.450
8
8
13
19
N
15
9
C
7
1.349
1.398
9
1.450
14
14
1.499
C
3
1.392
10
C
2
1.400
1.396
C
C
C
B
C
1.398
2
1.350
1
1.501
C
4
3
1.551
1.395
20
18
1.400
7
1
13
6
C
1.398
5
4
C
5
6
C
1.394
C
1.553
1.393
21
19
12
1.399
C
C
1.394
11
1.346
B
10
12
1.352
11
18
21
3a
3b
20
8
11
17
N
N
19
17
12
1.135
1.135
5
7
6
1.349
16
N
1.393
10
1.394
C
C
C
3
10
N
1.398
16
1.255
B
C
C
1.395
4
1.350
18
2
1.254
15
1
C
1.399
4
1.550
1.398
N
C
2
7
1.397
1
1.499
9
1.393
1.498
C
1.450
N
5 C
15
C
C
6
3
C
1.451
14
1.398
C
C
1.394
21
9
14
8
11
12
13
13
3c
4
Fig. 3. Equilibrium geometric parameters of 2ꢀ, 3ꢀ, and 4ꢀ(azidomethyl)phenylboronic acids 3a—c and benzylazide 4 according to the
results of quantumꢀchemical calculations by the AM1 method.

Synthesis of azidomethylphenylboronic acids
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
373
Table 1. Comparison of the energies of the corresponding MOs
for 2ꢀ(azidomethyl)phenylboronic acid 3a and benzylazide 4
Table 2. Electron density distribution in 2ꢀazidomethylphenylꢀ
boronic acid 3a and benzylazide 4
MOa
ε/a.u.b
MOa
ε/a.u.b
3а
4
Atom
Atomic charge*
Atom
Atomic charge*
3a
4
3a
4
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
H(7)
H(8)
–0.129583
–0.169245
+0.091189
+0.009110
–0.222649
–0.111503
+0.139874
+0.131598
–0.256747
+0.384770
+0.128239
+0.138001
+0.196240
+0.170793
–0.409588
+0.440290
–0.243026
–0.552856
–0.568089
+0.433838
+0.399344
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
H(7)
H(8)
–0.125372
–0.180997
+0.161466
–0.166365
–0.127988
–0.126673
+0.135695
+0.130766
–0.241161
+0.137907
+0.135782
+0.135082
+0.179307
+0.163966
–0.364637
+0.418706
–0.265484
–11 –0.41800
–10 –0.39003
–0.46271 +1
–0.44312 +2
–0.42806 +3
–0.42249 +4
–0.40897 +5
–0.36946 +6
–0.35849 +7
–0.34964 +8
–0.30096 +9
–0.04973
–0.03272
–0.01966
–0.00349
+0.07270
+0.07777
+0.09183
+0.11042
+0.12664
–0.02955
–0.01081
–0.00727
+0.01497
+0.08800
+0.11382
+0.12368
+0.14541
+0.15039
+0.15939
+0.17757
–9
–8
–7
–6
–5
–4
–3
–2
–1
0
–0.38048
–0.36793
–0.36519
–0.35734
–0.32239
–0.30798
–0.30403
–0.27530
–0.26503
–0.25886
C(9)
C(9)
B(10)
H(11)
H(12)
H(13)
H(14)
N(15)
N(16)
N(17)
O(18)
O(19)
H(20)
H(21)
H(10)
H(11)
H(12)
H(13)
H(14)
N(15)
N(16)
N(17)
–0.26146 +10 +0.13807
–0.25780 +11 +0.14553
–0.24693
a The numbering starts with the highest occupied molecular
orbital (numbered 0); the negative numbers correspond to the
occupied MOs; the positive numbers correspond to the virꢀ
tual MOs.
b The energy is expressed in atomic units (1 a.u. = 2625 kJ mol–1).
as well as by the semiempirical AM1 method.33 The strucꢀ
tures of compound 3a and benzylazide 4, which were
optimized at the B3LYP/6ꢀ31G(d) level of theory, are
presented in Fig. 2. It appeared that the results obtained
by the semiempirical AM1 method are in rather good
agreement with those obtained by the B3LYP/6ꢀ31G(d)
method. The geometric structures of compounds 3a, 3b,
3c, and 4 calculated by the AM1 method are shown
in Fig. 3.
The geometric parameters of the corresponding fragꢀ
ments in compounds 3a and 4 have close values. The
distance between the nitrene (N(15)) nitrogen atom (see
Fig. 2) and the nearest hydrogen atom in the residue of
boronic acid (0.1965 nm) is favorable for hydrogen bondꢀ
ing because it is smaller than the sum of the van der Waals
radii of the hydrogen and nitrogen atoms. Although the
distance between the nitrogen (N(15)) and the boron
atoms (0.3392 nm) is larger than the sum of the van der
Waals radii of these atoms (0.322 nm), the possibility of a
weak donorꢀacceptor interaction is not ruled out. The
energy levels in azides 3a and 4 are given in Table 1. The
* The charges are expressed in electron charge units.
theoretical bathochromic shift of the longꢀwavelength abꢀ
sorption maximum in the spectra of boronꢀcontaining
azide 3a compared to that of benzylazide is 8.3 nm. Earꢀ
lier, the bathochromic shift has been observed experiꢀ
mentally.25,34
The fact of formation of a weak donorꢀacceptor
N(15)→B bond is supported by a slight increase (by
0.0009 electron charge units) of the sum of the charges of
the nitrogen atoms in the azido group of compound 3a
compared to that of azide 4 (Table 2).
As can be seen from the aboveꢀdescribed results of
calculations, the geometric parameters of the azido group
in the benzylazide fragment remain unchanged upon the
insertion of boronꢀcontaining fragments at positions
2ꢀ, 3ꢀ, or 4 of the benzene ring (Table 3). The changes in
the energy of orbitals upon the above replacements are
Table 3. Bond lengths (d), bond angles (ω), and atomic charges (Z ) in the azido fragment of 2ꢀ, 3ꢀ, and
4ꢀ(azidomethyl)phenylboronic acids 3a—c and benzylazide 4 (calculations by the AM1 method)
Comꢀ
pound
d/nm
N(15)—N(16)
ω/deg
N(15)—N(16)—N(17)
Z/a.u.
N(16)—N(17)
N(15)
N(16)
N(17)
3a
3b
3c
4
0.126
0.125
0.126
0.125
0.113
0.114
0.114
0.114
169.0
169.2
169.0
169.1
–0.283
–0.285
–0.287
–0.286
0.217
0.218
0.219
0.221
–0.053
–0.052
–0.050
–0.057

374
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
Fedorov et al.
E/eV
3ꢀ(Bromomethyl)phenylboronic acid 2b. Compound 2b was
prepared in a yield of 0.29 g (37%) as a white powder, m.p.
0
217 °C (CH2Cl2—Et2O—hexane) (cf. lit. data38
: m.p.
–0.62
–0.85
–0.89
214—216 °C). 1H NMR (CDCl3), δ: 4.53 and 4.63 (both s,
intensity ratio 3 : 5, 2 H, CH2Br); 7.36—8.22 (m, 4 H, Ar—H).
13C NMR (CDCl3), δ: 33.3, 33.5 (CH2); 128.7 (C(5)); 131.9
(C(3)); 135.5; 135.8, 137.6 (C(2), C(4), C(6)). 11B NMR
(CDCl3), δ: 28.4.
–0.96
–2
–4
4ꢀ(Bromomethyl)phenylboronic acid 2c. Compound 2c was
prepared in a yield of 0.31 g (39%) as a white powder, m.p.
151 °C (CH2Cl2—Et2O—hexane) (cf. lit. data37
: m.p.
138—144 °C). 1H NMR (CDCl3), δ: 4.55 (s, 2 H, CH2); 7.50 (d,
2 H, H(3), H(5), J = 7.9 Hz); 8.12 (d, 2 H, H(2), H(6), J =
7.9 Hz). 13C NMR (CDCl3), δ: 33.6 (CH2); 129.2 (C(3)), (C(5));
136.7 (C(2)), (C(6)); 142.9 (C(4)).
–5.69
–5.92
–5.89
–6.00
–6
Synthesis of azidomethylphenylboronic acids 3a—c (general
procedure). (Bromomethyl)phenylboronic acid 2a—c (0.16 g,
0.74 mmol) was dissolved in dry DMF (5 mL) and then NaN3
(0.14 g, 2.2 mmol) was added. The reaction was carried out at
20 °C with vigorous stirring for 14 h. Then CHCl3 (30 mL) was
added to the reaction mixture. The organic layer was washed
with water (5×20 mL) and dried over anhydrous Na2SO4. Volaꢀ
tile products were distilled off under reduced pressure. The reacꢀ
tion product was precipitated with hexane from a solution
in CHCl3.
–8
–10
3a
3b
3c
4
Fig. 4. Electronic levels in 2ꢀ, 3ꢀ, and 4ꢀ(azidomethyl)phenylꢀ
boronic acids 3a—c and benzylazide 4 according to the results of
quantumꢀchemical calculations by the B3LYP/6ꢀ31G(d)//AM1
method.
2ꢀ(Azidomethyl)phenylboronic acid (3a). Solvate 3a•0.5 DMF
was obtained in a yield of 0.07 g (46%) as a viscous oil.
Found (%): C, 47.98; H, 5.04; N, 23.31. C17H23B2N7O5. Calcuꢀ
lated (%): C, 47.81; H, 5.43; N, 22.96. UV (EtOH), λ/nm (logε):
226 (3.868), 262 (3.159), 270 (3.229), 278 (3.096). 1H NMR
(CDCl3), δ: 2.98 and 3.02 (both s, 3 H each, Me); 4.48 and 4.88
(both s, intensity ratio 2 : 9, 4 H, CH2); 5.93 (s, 1 H, CHO);
7.27—7.68 (m, 6 H, H(3), H(4), H(5)); 8.09—8.24 (m, 2 H,
H(6)). 13C NMR (CDCl3), δ: 32.8, 37.9 (Me); 51.2 (CH2);
128.0; 129.8; 132.4; 136.7 (C(3), C(4), C(5), C(6)); 141.4(C(2));
163.6 (C=O). 11B NMR (CDCl3), δ: 28.9. IR (Nujol mulls),
ν/cm–1: 2080 (N3).
3ꢀ(Azidomethyl)phenylboronic acid (3b). Solvate 3b•0.5 DMF
was obtained in a yield of 0.077 g (48%) as a viscous oil.
Found (%): C, 48.09; H, 4.98; N, 23.31. C17H23B2N7O5. Calcuꢀ
lated (%): C, 47.81; H, 5.43; N, 22.96. UV (EtOH), λ/nm (logε):
225 (3.197), 264 (2.693), 270 (2.751), 277 (2.680). 1H NMR
(CDCl3), δ: 2.89 and 2.96 (both s, 3 H each, Me); 4.46 (br.s,
4 H, CH2); 5.86 (s, 1 H, CHO); 7.51—8.19 (m, 8 H, Ar—H).
13C NMR (CDCl3), δ: 32.8 (Me); 36.9 (Me); 54.8 (CH2); 128.5
(C(5)); 132.1 (C(3)); 135.0, 135.1, 137.4 (C(2), C(4), C(6));
162.9 (C=O). 11B NMR (CDCl3), δ: 27.4. IR (Nujol mulls),
ν/cm–1: 2070 (N3).
shown in Fig. 4. A decrease in the energy compared to the
corresponding values in benzylazide is associated with the
acceptor nature of the B(OH)2 fragment.
Experimental
The 1H and 13C NMR spectra were recorded on a Bruker
ACꢀ200P spectrometer; the chemical shifts are given in the δ
scale relative to Me4Si. The 11B NMR spectra were measured on
a Bruker ACꢀ200P instrument; the chemical shifts are given in
the δ scale relative to BF3•OEt2. The IR spectra were recorded
on a Specord 75ꢀIR spectrometer. The UV spectra were meaꢀ
sured on a SFꢀ46 spectrometer.
Methylphenylboronic acids 1a—c were prepared according
to known procedures.35,36
Synthesis of (bromomethyl)phenylboronic acids 2a—c (genꢀ
eral procedure). A mixture of methylphenylboronic acid 2a—c
(0.50 g, 3.68 mmol), NBS (0.69 g, 3.90 mmol), and (BzO)2
(0.09 g, 0.39 mmol) in CCl4 (30 mL) was refluxed for 2 h under
irradiation with an incandescent lamp (300 W). Then the reacꢀ
tion mixture was cooled to 40 °C and twice filtered through a
porous glass filter. The solvent was distilled off under reduced
pressure. The reaction product was washed with cold Et2O
(7 mL) and recrystallized from a CH2Cl2—Et2O—hexane
mixture.
2ꢀ(Bromomethyl)phenylboronic acid 2a. Compound 2a was
prepared in a yield of 0.46 g (58%) as a white powder, m.p. 138 °C
(CH2Cl2—Et2O—hexane) (cf. lit. data37: m.p. 139—146 °C).
1H NMR (CDCl3), δ: 4.75, 5.09, and 5.15 (all s, intensity ratio
3 : 3 : 14, 2 H, CH2Br); 7.28—7.54 (m, 3 H, H(3), H(4), H(5));
8.38 (d, 1 H, H(6), J = 8.1 Hz). 13C NMR (CDCl3), δ:
33.7, 35.3 (CH2Br); 128.2, 128.3, 130.6, 130.9, 132.7, 132.9,
137.7, 138.0 (C(3), C(4), C(5), C(6)); 145.4 (C(2)). 11B NMR
(CDCl3), δ: 33.0.
4ꢀ(Azidomethyl)phenylboronic acid (3c). Solvate 3c•0.5 DMF
was obtained in a yield of 0.075 g (49%) as a viscous oil.
Found (%): C, 48.06; H, 5.01, N, 23.38. C17H23B2N7O5. Calcuꢀ
lated (%): C, 47.81; H, 5.43; N, 22.96. UV (EtOH), λ/nm (logε):
232 (3.457), 264 (3.018), 269 (3.019), 276 (2.950). 1H NMR
(CDCl3), δ: 2.88 and 2.95 (both s, 3 H each, Me); 4.37 (s, 4 H,
CH2); 5.77 (s, 1 H, HCO); 7.31—7.46 (m, 4 H, H(3), H(5));
8.11—8.24 (m, 4 H, H(2), H(6)). 13C NMR (CDCl3), δ: 32.7
(Me); 36.8 (Me); 54.7 (CH2); 127.6 (C(3)), (C(5)); 136.1 (C(2)),
(Cꢀ6); 139.9 (C(4)), 163.1 (C=O). IR (Nujol mulls), ν/cm–1
:
2070 (N3).
Quantumꢀchemical calculations. The DFT and semiempirical
calculations were carried out using the GAMESS program.39

Synthesis of azidomethylphenylboronic acids
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
375
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This study was financially supported by the Russian
Foundation for Basic Research (Project Nos. 01ꢀ03ꢀ33113
and 02ꢀ03ꢀ33021), the Competition Center for Basic
Natural Science (PD02ꢀ1.3ꢀ443), and INTAS (Grant YSF
2002ꢀ122).
23. J. K. M. Sanders and B. K. Hunter, Modern NMR Spectrosꢀ
copy. A Guide for Chemists, Oxford University Press, New
York, 1997, 314 pp.
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Received November 1, 2002;
in revised form July 1, 2003