Synthesis of 1-(α-Aminobenzyl)-2-naphthol derivatives, their structure in crystal and in solution

Article abstract of DOI:10.1002/jhet.1978

The series of tautomeric 1,3-diarylnaphthoxazines (the Betti base precursors) was obtained by the interaction of 2-naphthols and 1,3,5-trisaryl-2,4-diazapenta-1,4-dienes. Their structure has been established in solid state and solution.

Full text of DOI:10.1002/jhet.1978

Month 2014 Synthesis of 1-(a-Aminobenzyl)-2-naphthol Derivatives, their Structure in
Crystal and in Solution
*
К. Е. Metlushka, D. N. Sadkova, L. N. Shaimardanova, A. I. Tufatullin, V. F. Zheltukhin, О. N. Kataeva,
and V. А. Alfonsov
A.E. Arbuzov Institute of Organic and Physical Chemistry of Kazan Scientific Centre of the Russian Academy of
Sciences, 420088 Arbuzov Str., 8, Kazan, Russia
*
E-mail: metlushka@mail.ru
Received December 10, 2012
DOI 10.1002/jhet.1978
Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com).
The series of tautomeric 1,3-diarylnaphthoxazines (the Betti base precursors) was obtained by the interac-
tion of 2-naphthols and 1,3,5-trisaryl-2,4-diazapenta-1,4-dienes. Their structure has been established in solid
state and solution.
J. Heterocyclic Chem., 00, 00 (2014).
INTRODUCTION
literature data [4–8], compounds 3a–3j in CDCl3 solution
are present as a mixture of tautomers A, B, and C because
of the ring-chain tautomerism.
1-(a-Aminobenzyl)-2-naphthol is the chiral compound for
the first time obtained by the Italian scientist Mario Betti in
the first decade of the last century. Its derivatives have
recently attracted the attention of researchers who work on
asymmetric syntheses because of the need for new easily
accessible chiral enantiopure compounds that can be used
as auxiliaries or precursors. 1-(a-Aminobenzyl)-2-naphthols,
named in honor of the author of these compounds, the Betti
bases, are quite suitable for these purposes because of the
ease of synthesis, the availability of the initial reagents, and
potential for enantiomeric separation. Surprisingly enough
for a long time, this class of compounds did not attract proper
attention until recently, when several publications appeared
in this field [1,2] owing to the progress in stereochemistry
and the synthesis of enantiopure medicines.
Compounds 3g, 3i, and 3j were previously synthesized
using standard Betti method [9,10], the obtained results
raising some doubts. The difference in melting points
between our and literature data reaches in certain cases about
70ꢀC, and 1Н NMR studies exhibit the presence of only one
tautomer, which is impossible for this sort of compounds.
Because of significant discrepancies between our and
literature data, it is necessary to give full description of
obtained products 3g–3j. As it was expected, all compounds
3g–3j in the CDCl3 solution exist as a mixture of tautomers
А, В, and С because of the ring-chain tautomerism. The ratio
of tautomers, as determined by integration of proton signals
at C1 and C3, is given in Table 1.
Differentiation and classification of tautomers were
carried out in accordance with the literature data [4,5]. It is
necessary to note that tautomers’ ratio for compounds 3g–3j
is almost the same as tautomers’ ratio for 1,3-naphthoxazines
derived from 2-naphthol with the same substitutes. Notice
that the ratio of imine tautomer increases with rising of donor
ability of substituents in aryl fragments and reveals maximum
for dimethylamino-substituted derivative.
Thus, condensation products of Betti bases with various
aldehydes in solution exist in three tautomeric forms, because
of oxazine-imine tautomeric equilibrium. However, these
compounds are not as well studied in the solid phase. To
RESULTS AND DISCUSSION
Recently, we reported a new approach to the synthesis of
1,3-diaryl-2,3-dihydro-1Н-naphtho[1,2-е][1,3]oxazines – Betti
base derivatives. The method involves the interaction of 2-
naphthol 1 with very accessible 1,3,5-trisaryl-2,4-diazapenta-
1,4-dienes 2 in molar ratio 3:2 in boiling benzene (Scheme 1)
[3]. To expand the boundaries of proposed method, 6-bromo-
2-naphthol was used in the reaction with 1,3,5-trisaryl-
2,4-diazapenta-1,4-dienes 2c–2f resulting in formation of
3g–3j with good yield and purity. In accordance with the
© 2014 HeteroCorporation

К. Е. Metlushka, D. N. Sadkova, L. N. Shaimardanova, A. I. Tufatullin, V. F. Zheltukhin,
О. N. Kataeva, and V. А. Alfonsov
Vol 000
Scheme 1. Preparation of 1,3-diarylnaphthoxazines 3a–3j.
Scheme 2. Preparation of 1-phenyl-3-arylnaphthoxazines 4a–4d.
all products have a cyclic structure (B and C). IR spectra
of these compounds in KBr pellets had no absorption
bands corresponding to the C═N group and contained
two sharp bands at 1600–1610 and 1620–1630 сmꢁ1
,
except the dimethylamino-substituted derivative, which
possessed a broad band in the region 1570–1630 сmꢁ1
.
IR spectra of their solution in chloroform had an
additional band at 1650–1660 сmꢁ1, attributed to the
C═N group of imine tautomer A, which is in equilibrium
with trans-naphthoxazine (B) and cis-naphthoxazine (C)
cyclic tautomers.
The analysis of the IR spectra of compounds 3а–3j
recorded by us in KBr pellets allows to divide them into
two groups (Table 2). The first group (compounds 3a–3d
and 3g–3i) has two sharp absorption bands at 1587–1598
and 1612–1624 сmꢁ1. The second one (compounds
3e, 3f, and 3j) has three bands in this region: 1575–1579,
1604–1608, and 1637–1646 cmꢁ1. We assign two bands
of the first group to the valence C═C vibrations of the
naphthol fragment of the oxazine cycle. The third band at
1637–1646 сmꢁ1 in the spectra of compounds 3e, 3f,
and 3j corresponds to the valence C═N vibrations of the
acyclic tautomer and the valence C═C vibration bands
Table 1
Yields, melting points, tautomer ratio in solution of CDCl3 for
compounds 3g–3j.
Tautomer ratio, %,
according to Н
1
NMR
Product
R
X
Yield, % mp ꢀC
A
B
C
3g
3h
3i
H
Br
Br
94
84
91
86
142–143
148–150
170–172
196–197
28
42
58
92
62
51
36
7
10
7
6
Me
OMe Br
NMe2 Br
being shifted approximately by 5–20 сmꢁ1
. Thus,
3j
~1
compounds 3a–3d and 3g–3i in the solid state have most
probably oxazine structure, whereas compounds 3e, 3f,
and 3j have imine form.
provide full-scale range of variety of these compounds,
we obtained a number of model compounds 4a–4d
prepared using standard procedure [4] from unsubstituted
1-(a-aminobenzyl)-2-naphthol and the corresponding
para-substituted benzaldehydes (Scheme 2). In contrast to
compounds 3a–3j, they do not have a substituent in one of
the aryl rings. Compounds 3a–3j and 4a–4d were studied
in the crystalline phase by vibrational spectroscopy.
One more distinctive feature of cyclic tautomers В and
С in comparison with chain form А is the sharp band at
3308–3329 сmꢁ1 for compounds 3а–3d, and 3g–3i, which
may be assigned to the valence vibrations of the free NH
bond, which is present only in the cyclic oxazine structure
and absent in imine form. On the contrary, for compounds
3e, 3f, and 3j, containing electron donor substitutents, the
major spectral feature is the broad absorption band at
2000–3000 сmꢁ1, which gives evidence of the strong
hydrogen bond of OH group with imine nitrogen
О-Н⋯N═С. In the cyclic derivatives, there are no bands
in this region of the IR spectra.
It should be noted that the group of German authors [7]
ascribe the imine structure to compound 3c owing to
the presence of absorption band at 1618 cmꢁ1 in the IR
spectra, which they attributed to the valence vibrations
of the imino-group. However, according to Smith and
1
Compounds 4a–4d bearing substituents only in the
aromatic fragment at imino-nitrogen have the same spec-
tral features. According to their spectra, para-nitro- 4a
and para-bromo- 4b derivatives are cyclic tautomers,
Cooper, who published the results of H NMR and IR
spectroscopic studies of ring-chain tautomerism of some
condensation products of racemic 1-a-(aminobenzyl)-2-
naphthol with aromatic aldehydes in the solid state [8],
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2014
Synthesis of 1-(Alpha-Aminobenzyl)-2-naphthol Derivatives, their Structure in Crystal
and in Solution
Table 2
Characteristic IR absorption bands (сmꢁ1) of 3a–3j and 4a–d, and 5; 2-naphthol and 2-methoxynaphthalene.
Compound
No.
R
nC═N
nC═C arom.
nNH-free
3a
3b
3c
3d
3e
3f
Br
Cl
H
CH3
OCH3
N(CH3)2
—
—
—
—
1646
1642
1597, 1624
1598, 1623
1598, 1623
1598, 1623
1575, 1608
1579, 1604
3311
3316
3319
3308
—
—
3g
3h
3i
H
CH3
OCH3
N(CH3)2
—
—
—
1590, 1618
1587, 1613
1588, 1612
1578, 1605
3311
3311
3329
—
3j
1637
4a
4b
4c
4d
NO2
Br
OCH3
N(CH3)2
—
—
1641
1633
1598, 1620
1595, 1619
1580, 1598
1582, 1604
3307
3313
—
—
5
—
1640
1578, 1596
—
2-naphthol
2-methoxynaphthalene
1а
—
—
—
—
—
1600, 1630
1597, 1630
—
—
whereas para-methoxy- 4c and para-dimethylamino- 4d
derivatives can be ascribed to acyclic forms (Table 2).
With the purpose to obtain exclusively imine tautomer,
we have synthesized O-methylated derivative 5 starting
from 3с.
Compound 5 has been obtained first in multistep synthesis
from 1-iodo-2-naphthol [11] and characterized only with
melting point and elemental analysis. As an intermediate,
it is appeared in the paper [12] without isolation from the
reaction mixture and characterization. We have obtained
pure 5 in reaction of 3с with methyl iodide in the presence
of alkali (Scheme 3). The IR spectra of compound 5 has an
absorption band at 1640cmꢁ1, characteristic of valence
vibrations of the imine group (Table 2), whereas the bands
of the aromatic naphthyl fragment are present as the signals
at 1578 and 1596 сmꢁ1
.
Conclusions about the structure of products 3 and 4 in
crystalline phase, which we have made on the basis of
the IR spectra, were confirmed by X-ray diffraction study
of optically active condensation products (S)-(+)-3с
and (S)-(+)-4d, which were obtained from (S)-(+)-1-
(a-aminobenzyl)-2-naphthol and benzaldehyde, as well
as p-dimethylaminobenzaldehyde. Unsubstituted product
(S)-(+)-3с, as well as its bromine derivative, is
crystallized as a cyclic isomer (Fig. 1(a)) [13], whereas
dimethylaminoderivative (S)-(+)-4d is acyclic in crystalline
phase (Fig. 1(b)). X-Ray study shows that the N-H group
in oxazine structure (S)-(+)-3с is sterically hindered and does
Scheme 3. Preparation of OMe derivative 5.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

К. Е. Metlushka, D. N. Sadkova, L. N. Shaimardanova, A. I. Tufatullin, V. F. Zheltukhin,
О. N. Kataeva, and V. А. Alfonsov
Vol 000
(a)
(b)
Figure 1. Molecular structure of oxazine (S)-(+)-3с (а) and imine (S)-(+)-4d (b).
CONCLUSIONS
The number of new Betti base derivatives was obtained
by the interaction of 6-bromo-2-naphthol and 1,3,5-
trisaryl-2,4-diazapenta-1,4-dienes, which shows versatility
of proposed method of syntheses of such compounds.
It was established that 1,3-diarylnaphthoxazines might
crystallize in acyclic or cyclic forms depending on substituents
in aromatic fragments. The increase of the donor ability
of substituents in aryl fragments leads to crystallization of
these compounds in the form of imine (acyclic) tautomer,
which correlates with the enlarged share of imine tautomer
in their solutions.
It was shown that analysis of the IR spectra of 1,3-
diarylnaphthoxazines bearing substituents in one or in both
aryl fragments allows to clearly define their structure in
solid state on the basis of characteristic absorption bands
corresponding to the C═C, C═N, and N-H groups. These
conclusions, made from IR spectra, were unambiguously
confirmed by X-ray single-crystal diffraction.
Figure 2. Molecular structure of compound 5.
not participate in hydrogen bonding. Oxazine structure of the
compound (S)-(+)-3с has a twist conformation with four
atoms, O3, C4, C5, and C6 located in the plane of naphthyl
fragment, and atoms N1 and C2 moved out on different sides
of this plane by approximately equal distance (0.37 Å).
Phenyl substituents are in trans position to the six-membered
oxazine cycle. That is, the trans isomer is crystallized, which
predominates in solution.
EXPERIMENTAL
1H NMR spectra were recorded on an AVANCE-600 (600.13
MHz) spectrometer (Bruker, Germany) with TMS as the external
reference. The following abbreviations are used to indicate
multiplicities: s: singlet; m: multiplet. IR spectra were recorded
on a Vector 22 spectrometer (Bruker AXS GmbH, Karlsruhe,
Germany) from KBr pellets. Melting points were measured on a
Boetius melting point microscope.
Imine structure (S)-(+)-4d promotes the formation of an
intramolecular hydrogen bond between the naphthyloxy
hydrogen atom and imine nitrogen with the formation
of the thermodynamically favorable six-membered ring
(Fig. 1(b)). The strong intramolecular hydrogen bonds
are also evident from the IR spectra in the region
X-ray data for (S)-(+)-3с, (S)-(+)-4а and 5 were collected with a
Nonius KappaCCD diffractometer (Bruker AXS GmbH, Karlsruhe,
Germany) equipped with a molybdenum fine-focus sealed tube
(compound (S)-(+)-3с was reported earlier by us [14], coordinates
of atoms deposited in Cambridge Crystallographic Data Centre:
CCDC 628868). Programs used: data collection COLLECT (Nonius
B.V., 1998), Denzo-SMN [15], absorption correction SORTAV
[16,17], structure solution – SHELXS-97 [18], and structure refine-
ment SHELXL-97 [19]. Crystal data for (S)-(+)-4а: C26H24N2O,
M= 380.47, colorless plates, orthorhombic, space group P212121,
Z=4, a= 6.462(1), b= 16.041(1), c= 19.914(1) Å, V= 2064.2(4)
Å3, rcalc = 1.224 g ꢂ cmꢁ3, m =0.75 cmꢁ1, l = 0.71073 Å, T= 293(2)
2000–3000 сmꢁ1
.
Compound 5 (Fig. 2) has also been studied by X-ray
single-crystal diffraction. Because of the absence of the
intramolecular hydrogen bond in O-methylated derivative
(compared with (S)-(+)-4d structure, Fig. 1(b)), the
naphthyl fragment plane in compound 5 is rotated about
C3-C4 bond and is eclipsed with the proton at C3, which
minimize the steric interactions of phenyl groups at C2
and C3 with the naphthyl moiety.
K, 16432 reflections collected (ꢃh, ꢃk, ꢃl), [(sinθ)/l] = 0.60 Åꢁ1
,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2014
Synthesis of 1-(Alpha-Aminobenzyl)-2-naphthol Derivatives, their Structure in Crystal
and in Solution
3758 independent (Rint = 0.043) and 2800 observed reflections
[I≥2s(I)], 267 refined parameters, R1 = 0.0439, wR2 = 0.0828, and
goodness of fit 1.165. Crystal data for 5: C25H21NO, M= 351.43,
colorless block, monoclinic, space group P21/n, Z=4, a= 8.299(1),
b= 24.051(1), c= 9.934(1) Å, b = 106.08(3)º, V= 1905.2(3) Å3,
6.83–7.96 (m, CHarom); IR (KBr): n 1588, 1612 (С═Сarom), 3329
(NH). Anal. Calcd. for C26H22BrNO3: C, 65.55; H, 4.66; Br,
16.77; N, 2.94. Found: C, 65.61; H, 4.71; Br, 16.90; N, 3.01.
1-[a-(4-Dimethylaminobenzylidene)amino-4-dimethylamino-
benzyl]-6-bromonaphth-2-ol (3j). The mixture of 6-bromo-2-
naphthol (1b, 0.4 g, 1.8 mmoles) and 1,3,5-tris (4-dimethylamino-
phenyl)-2,4-diazapenta-1,4-diene (2f, 0.51 g, 1.2 mmoles) in
benzene (5mL) was heated under reflux for 6 h. The precipitated
product was filtered off and recrystallized from benzene to give
0.77g (86%) of 3j; mp: 196–197ꢀC (ref. [9]; mp: 120ꢀC); 1H
r
calc = 1.225 g ꢂ cmꢁ3, m =0.74cmꢁ1, l = 0.71073 Å, T= 198(2) K,
27193 reflections collected (ꢃh, ꢃk, ꢃl), [(sinθ)/l]=0.66Åꢁ1
,
4391 independent (Rint = 0.032) and 3233 observed reflections
[I≥2s(I)], 245 refined parameters, R1 = 0.0384, wR2 = 0.0876, and
goodness of fit 1.027. Absolute configuration of (S)-(+)-4а was
not determined but assumed from the initial Betti base. Supplemen-
tary crystallographic data sets for the structures of (S)-(+)-4а and 5
are available through the Cambridge Structural Database with
deposition numbers 890339 (for (S)-(+)-4а) and 890338 (for 5).
1,3,5-Trisaryl-2,4-diazapenta-1,4-dienes 2a–2f were prepared
according to the known method [20]. 1,3-diarylnaphthoxazines
3a–3j were obtained by interaction of 2-naphthols 1 with 1,3,5-
trisaryl-2,4-diazapenta-1,4-dienes 2 following the method [3].
Tautomeric ratio (A, B, and C) for compounds 3g–3j was deter-
0
NMR (CDCl3): d (tautomer A) 2.89 (s, NMe2), 3.04 (s, NMe2 ),
6.24 (s, CHN), 8.41 (s, CH═N), (tautomer B) 2.95 (s, NMe2),
0
2.97 (s, NMe2 ), 5.57, 5.71 (2s, CHN), (tautomer C) 5.78, 5.85
(2s, CHN), (tautomers A + B + C) 6.63–7.91 (m, CHarom); IR
(KBr): n 1578, 1605 (С═Сarom), 1637 (C═N). Anal. Calcd. for
C28H28BrN3O: C, 66.93; H, 5.62; Br, 15.90; N, 8.36. Found: C,
66.71; H, 5.53; Br, 16.08; N, 8.48.
1-(a-Benzylidenaminobenzyl)-2-methoxynaphthaline (5). The
compound was obtained by the method described in [12] with our
modifications. 1,3-diphenylnaphthoxazine (3c, 10.12 g, 0.03 mole)
was dissolved in mixture of dry dioxane (60 mL) and dry acetone
(80 mL) under heating till 50ꢀC. The solution was cooled to 0ꢀC,
and powdered NaOH (1.8 g, 0.045 mole) was added. Afterwards,
methyl iodide (11.45 g, 0.08 mole) was added dropwise at 0ꢀC.
After the addition of methyl iodide, the reaction mixture was stirred
at room temperature for 8 h. The next day, the precipitate of NaI
was filtered off and washed with ethyl acetate (50 mL ꢄ 2), and the
filtrate was dried over Na2SO4 and combined with mother liquor.
Solvents were removed in vacuo, and resulting dense residue was
extracted by absolute ethyl alcohol (80 mL) at 60ꢀC. The obtained
precipitate was separated and extracted with diethyl ether. The
ether extract was separated, and on cooling, it dropped out of the
crystalline product 5. The latter was filtered off. Extraction was
repeated until complete isolation of the product to give 6.2 g (59%)
of 5. Analytically pure sample was obtained by recrystallization
1
mined by integration of proton signals in Н NMR spectra and
given in Table 1. 1-(a-Aminobenzyl)-naphthol-2 was prepared by
the hydrolysis of 1,3-diphenylnaphthoxazine 3с following the method
[21]. Its condensation with a series of substituted benzaldehydes
(p-nitro-, p-bromo-, p-methoxy- and p-dimethylamino- derivatives)
gave oxazines 4а–4d [4,5]. Compounds (S)-(+)-3с and (S)-(+)-4а
were obtained following the method [12].
1-[a-(Benzylidene)aminobenzyl]-6-bromonaphth-2-ol (3g).The
mixture of 6-bromo-2-naphthol (1b, 0.4g, 1.8 mmoles) and 1,3,5-
trisphenyl-2,4-diazapenta-1,4-diene (2c, 0.36 g, 1.2 mmoles) in
benzene (5 mL) was heated under reflux for 14 h. The precipitated
product was filtered off and recrystallized from benzene to give
0.7 g (94%) of 3g; mp: 142–143ꢀC (ref. [9]; mp: 100ꢀC, ref. [10];
mp: 150–152ꢀC); 1H NMR (CDCl3): d (tautomer A) 6.41
(s, CHN), 8.63 (s, CH═N), (tautomer B) 5.63, 5.72 (2s, CHN),
(tautomer C) 5.86, 5.94 (2s, CHN), (tautomers A + B + C)
7.26–7.96 (m, CHarom); IR (KBr): n 1590, 1618 (С═Сarom),
3320 (NH). Anal. Calcd. for C24H18BrNO: C, 69.24; H, 4.36;
Br, 19.19; N, 3.36. Found: C, 69.03; H, 4.10; Br, 19.45; N, 3.50.
1-[a-(4-Methylbenzylidene)amino-4-methylbenzyl]-6-
bromonaphth-2-ol (3h). The mixture of 6-bromo-2-naphthol (1b,
0.4 g, 1.8 mmoles) and 1,3,5-tris(4-methylphenyl)-2,4-diazapenta-
1,4-diene (2d, 0.4 g, 1.2 mmoles) in benzene (5mL) was heated
under reflux for 10h. The precipitated product was filtered off
and recrystallized from benzene to give 0.67 g (84%) of 3h; mp:
148–150ꢀC; 1H NMR (CDCl3): d (tautomer A) 2.21 (s, Me), 2.33
(s, Me0), 6.25 (s, CHN), 8.47 (s, CH═N), (tautomer B) 2.27
(s, Me), 2.29 (s, Me0), 5.49, 5.61 (2s, CHN), (tautomer C) 2.23
(s, Me), 2.35 (s, Me0), 5.72, 5.80 (2s, CHN), (tautomers A +B + C)
7.01–7.86 (m, CHarom); IR (KBr): n 1587, 1613 (С═Сarom), 3311
(NH). Anal. Calcd. for C26H22BrNO: C, 70.28; H, 4.99; Br, 17.98;
N, 3.15. Found: C, 69.97; H, 4.70; Br, 17.85; N, 3.08.
1-[a-(4-Methoxybenzylidene)amino-4-methoxybenzyl]-
6-bromonaphth-2-ol (3i). The mixture of 6-bromo-2-naphthol
(1b, 0.4 g, 1.8 mmoles) and1,3,5-tris(4-methoxyphenyl)-2,4-
diazapenta-1,4-diene (2e, 0.46g, 1.2 mmoles) in benzene (5 mL)
was heated under reflux for 10 h. The precipitated product was
filtered off and recrystallized from benzene to give 0.78 g (91%)
of 3i; mp: 170–172ꢀC (ref. [10]; mp: 162–164ꢀC); 1H NMR
(CDCl3): d (tautomer A) 3.77 (s, OMe), 3.88 (s, OMe0), 6.32
(s, CHN), 8.53 (s, CH═N), (tautomer B) 3.82 (s, OMe), 3.85
(s, OMe0), 5.60, 5.69 (2s, CHN), (tautomer C) 3.79 (s, OMe),
3.93 (s, OMe0), 5.81, 5.89 (2s, CHN), (tautomers A + B + C)
1
from ether. mp: 106–108ꢀC (ref. [11]; mp: 104–106ꢀC); Н NMR
(CDCl3): d 4.03 (s, 3Н, OCH3), 6.91 (s, 1H, CHN), 7.19–8.24 (m,
16Н, CHarom), 8.49 (s, 1Н, СН═N); IR (cmꢁ1): n 1578, 1596
(С═Сarom), 1640 (C═N). Anal. Calcd. for C25H21NO: C, 85.44; H,
6.02; N, 3.99. Found: C, 85.05; H, 6.08; N, 4.12.
Acknowledgments. This work was supported by the Russian
Foundation for Basic Research (grants no. 11-03-00463 and 11-03-
90449) and by the Ministry of Education and Science of the Russian
Federation (grant no. 8446).
REFERENCES AND NOTES
[1] Szatmári, I.; Fülöp, F. Curr Org Synth 2004, 1, 155.
[2] Cardellicchio, C.; Capozzi, M.A.M.; Naso, F. Tetrahedron:
Asymmetry 2010, 21, 507.
[3] Zheltukhin, V.F.; Metlushka, K.E.; Sadkova, D.N.; McKenna, C.E.;
Kashemirov B.A.; Alfonsov V.A. Mendeleev Commun 2007, 17, 239.
[4] Szatmári, I.; Martinek, T.A.; Lázár, L.; Fülöp, F. Tetrahedron
2003, 59, 2877.
[5] Szatmári, I.; Martinek, T.A.; Lázár, L.; Koch, A.; Kleinpeter,
E.; Neuvonen, K.; Fülöp, F. J Org Chem 2004, 69, 3645.
[6] Tóth, D.; Szatmári, I.; Fülöp, F. Eur J Org Chem 2006, 4664.
[7] Möhrle, H.; Miller, C.; Wendisch, D. Chem Ber 1974, 107, 2675.
[8] Smith, H.E.; Cooper, N.E. J Org Chem 1970, 35, 2212.
[9] Chopde, H.N.; Meshram, J.S.; Pagadala, R.; Mungole, A.J.
Int J ChemTech Res 2010, 2, 1823.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

К. Е. Metlushka, D. N. Sadkova, L. N. Shaimardanova, A. I. Tufatullin, V. F. Zheltukhin,
О. N. Kataeva, and V. А. Alfonsov
Vol 000
[10] Mayekar, A.N.; Yathirajan, H.S.; Narayana, B.; Sarojini, B.K.;
Suchetha Kumari, N.; Harrison, W.T.A. Int J Chem 2011, 3, 74.
[11] Ray, F.E.; Moomaw, W.A. J Am Chem Soc 1933, 55, 3833.
[12] Cardellicchio, C.; Ciccarella, G.; Naso, F.; Schingaro, E.;
Scordari, F. Tetrahedron: Asymmetry 1998, 9, 3667.
[13] Jasinski, J.P.; Pek, A.E.; Mayekar, A.N.; Yathirajan, H.S.;
Narayana, B. Acta Crystallogr Sect E 2010, E66, o2053.
[14] Alfonsov, V.A.; Metlushka, K.E.; McKenna, C.E.;
Kashemirov, B.A.; Kataeva, O.N.; Zheltukhin, V.F.; Sadkova, D.N.;
Dobrynin, A.B. Synlett 2007, 488.
[15] Otwinowski, Z.; Minor, W. Methods Enzymol 1997,
276, 307.
[16] Blessing, R.H. Acta Crystallogr Sect A 1995, 51, 33.
[17] Blessing, R.H. J Appl Crystallogr 1997, 30, 421.
[18] Sheldrick, G.M. Acta Crystallogr Sect A 1990, 46, 467.
[19] Sheldrick, G.M. (1997) SHELXL97 a computer program for
crystal structure determination Unuversity for Gottingen
[20] Katritzky, A.R.; Wang, X.; Maimait, R. J Org Chem 2000,
65, 8077.
[21] Betti, M. Org Synth Coll Vol 1941, I, 381.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet