Base-induced transformations of ortho-nitrobenzylketones: Intramolecular displacement of nitro group versus nitro-nitrite rearrangement

Article abstract of DOI:10.1016/j.tet.2012.05.034

Reactions of 4-bromo-5-nitrophthalonitrile (BNPN) with enolates of alkyl 4-R-2,4-dioxobutanoates gave alkyl 3-acyl-5,6-dicyanobenzofuran-2-carboxylates, 4-(2-R-2-oxoethyl)-5-nitrophthalonitriles, or 3-acyl-1,2-benzoxazole-5,6- dicarbonitriles. With a base, 4-(2-R-2-oxoethyl)-5-nitrophthalonitriles either undergo nitro-nitrite rearrangement resulting in 3-acyl-1,2-benzoxazole-5,6- dicarbonitriles or yield 2-R-benzofuran-5,6-dicarbonitriles with a nitro group displacement.

Full text of DOI:10.1016/j.tet.2012.05.034

Tetrahedron 68 (2012) 5991e5997
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Base-induced transformations of ortho-nitrobenzylketones: intramolecular
displacement of nitro group versus nitro-nitrite rearrangement
,
a
,
,
,
z
Sergey I. Filimonov a , Zhanna V. Chirkova y, Igor G. Abramova y, Sergey I. Firgang b
,
*
Galina A. Stashina b z, Yuri A. Strelenko b z, Dmxitriy V. Khakimov b z, Tatyana S. Pivina b
,
,
,
,
,
z
Alexander V. Samet b z, Kyrill Yu. Suponitsky c
,
,
a Yaroslavl State Technical University, 88 Moskovsky Pr, 150023 Yaroslavl, Russian Federation
b N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky Pr., 119991 Moscow, Russia
c A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilov St., 119991 Moscow, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of 4-bromo-5-nitrophthalonitrile (BNPN) with enolates of alkyl 4-R-2,4-dioxobutanoates gave
alkyl 3-acyl-5,6-dicyanobenzofuran-2-carboxylates, 4-(2-R-2-oxoethyl)-5-nitrophthalonitriles, or 3-acyl-
1,2-benzoxazole-5,6-dicarbonitriles. With a base, 4-(2-R-2-oxoethyl)-5-nitrophthalonitriles either un-
dergo nitro-nitrite rearrangement resulting in 3-acyl-1,2-benzoxazole-5,6-dicarbonitriles or yield 2-R-
benzofuran-5,6-dicarbonitriles with a nitro group displacement.
Received 27 February 2012
Received in revised form 27 April 2012
Accepted 8 May 2012
Available online 18 May 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
4-Bromo-5-nitrophthalonitrile
4-(2-R-2-Oxoethyl)-5-nitrophthalonitriles
1,2-Benzoxazole-5,6-dicarbonitriles
Alkyl 5,6-Dicyanobenzofuran-2-
carboxylates
1-Hydroxyindole-5,6-dicarbonitriles
Nitro-nitrite rearrangement
1. Introduction
position via SNAr-reaction of 4-bromo-5-nitrophthalonitrile (BNPN)
with sodium enolates of alkyl 2,4-dioxobutanoates 2aed. The use of
SNAr-reactions are of significant interest both from theoretical1
and practical2,3 points of view. Consecutive C-,O-nucleophilic sub-
stitution of ortho-located leaving groups (Hal, NO2) in various
substrates with 1,3-dicarbonyl compounds results in 2,3-
disubstituted benzofurans.4e6 At the same time, 2-
carboxybenzofurans were not obtained via SNAr-reaction so far.
Known methods for the synthesis of these compounds include
intramolecular cyclization of the corresponding O-substituted sal-
icylaldehyde derivatives7 or ortho-alkynyl phenyl ethers.8 Interest
in the synthesis of 2-carboxybenzofurans is due to the fact that the
latter are used as precursors in the synthesis of biologically active
compounds.9e11
these compounds as ambident nucleophiles was not described
previously. At the same time, BNPN 1 is well-known as one of the
active substrates for the preparation of various heterocyclic sys-
tems annulated with a phthalonitrile fragment.12e14 ortho-Dicar-
bonitriles serve as
a starting material for the synthesis of
macroheterocycles15 (hexazocyclanes, phthalocyanines).
2. Results and discussion
We found that, depending on the temperature, the reaction of 1
with 2 in 1:2 ratio (or reaction between 1 and alkyl 2,4-
dioxobutanoates (1:1) in the presence of K2CO3) affords either 4,
5, 6 or their mixtures. Detailed 1H NMR study of the reaction of
substrate 1 with 2a (DMSO-d6, 25 ꢀC) revealed the formation and
accumulation of a single compound, which was assigned the
structure of 3a. Such assignment is based on upfield 1H NMR
chemical shifts of the protons of phthalonitrile moiety (7.55 and
8.34 ppm) compared to those of the same protons in products 4, 5,
6. When the reaction mixture was diluted with water, enolates 3
were found to undergo hydrolytic cleavage16e18 (retro-Claisen
Our work was aimed at the synthesis of previously unknown
benzofuran-5,6-dicarbonitriles with alkoxycarbonyl group in 2-
* Corresponding author. Fax: þ7 4852 44 07 29; e-mail addresses: filimonovsi@
ystu.ru (S.I. Filimonov), sametav@server.ioc.ac.ru (A.V. Samet).
y
Fax: þ7 4852 44 07 29.
z
Fax: þ7 495 135 53 28.
x
Fax: þ7 499 135 92 02.
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.05.034

5992
S.I. Filimonov et al. / Tetrahedron 68 (2012) 5991e5997
reaction) yielding a mixture of 5 and 6; meanwhile, when the re-
action occurred at rt and the reaction mixture was diluted with 5%
aqueous HCl, only 4-(2-aryl-2-oxoethyl)-5-nitrophthalonitriles
5aec were formed in 67e75% yields (Scheme 1).
Intramolecular cyclization reactions of ortho-substituted nitro-
aromatic compounds (such as 5) are known.21,22 Usually they afford
derivatives of anthranyl (2,1-benzoxazole) 10, while in our case
only 1,2-benzoxazoles 6 were formed. To the best of our knowledge,
formation of 6 from 5 was not previously described in literature.
The structure of 5 and 6 was confirmed by NMR- and mass-
spectroscopy data.
When the reaction was carried out at rt as in the previously
described synthesis,6 formation of benzofurans 4 was not observed.
The latter were isolated together with the corresponding 1,2-
benzoxazoles 6aec upon heating of the starting reagents 1 and 2
in 1:2 ratio at 60e80 ꢀC for 12 h. Low yields of the target products
4aec (20e30%) are caused by side reactions (primarily, by the
formation of 6). Increasing temperature to 80e100 ꢀC afforded 1,2-
benzoxazoles 6 in yields up to 23%. As target products, benzofurans
4 were prepared in moderate yields (up to 35%) from alkyl 2,4-
dioxobutanoates 20aed in the presence of K2CO3 (2-fold excess)
at 60e80 ꢀC for 6e8 h.
Unequivocal proof of the position of O and N atoms in hetero-
cycles 6 was obtained by a single crystal X-ray study of 6b.23 The
single crystals were obtained from THF solution. A general view of
6b is shown in Fig. 2. The asymmetric unit cell contains two crys-
tallographically independent molecules A and A0. Both molecules
have more planar structure in comparison to 4a. The structures of A
and A0 can be described as built up of two
p-conjugated fragments
linked by single C3eC8 bond. The difference between the two in-
dependent molecules is in the relative orientation of these planar
fragments (torsion angles N2eC3eC8eC9 are equal to 8.3(8)ꢀ and
26.4(8)ꢀ for A and A0, respectively). Another difference is in orien-
tation of methoxy group. In both molecules it is in the plane of
corresponding Ph-cycle, but in A, it is oriented cis while in A0, it is
trans to C11eC12 bond.
Formation of the products 6 from 5 became evident from further
investigations. Thus, heating 5 in DMF at 80 ꢀC for 5e6 h afforded
products 6 in up to 85% yields, while the addition of Et3N shortened
the reaction time to 1e2 h.
Cyclization of the intermediates 3 could afford two isomeric
benzofurans 4 and 7. Strong evidence in favor of formation of the
products 4 is provided by mass-spectra where the most intensive
peaks (100%) correspond to benzoyl-cations (COeRþ).
O
O
COOR1
R
R
N
N
N
N
COOR1
O
O
We found that upon addition of Et3N (2 equiv) to a solution of
compounds 5aec in DMSO (or DMF) the mixture turned bluish-
7
4
green due to the formation of anionic intermediate24e26
8
(Scheme 2), which was studied by 2D 1He1H and 1He13C NMR
spectroscopy (in an NMR-tube). Thus, 1H NMR spectrum of 8a
(Table 1) showed a strong downfield shift of H-6 signal (9.86 ppm)
while the signal of methylene group disappeared and a signal of
methyn proton appeared instead (7.31 ppm). In addition, 13C NMR
spectrum showed an upfield shift of C-4 (91.2 ppm) and C-5
(113.7 ppm) signals thus indicating partial loss of aromaticity of the
benzene ring.
The structure of the products was confirmed by X-ray diffraction
data for 4a.19 The single crystals of 4a were obtained from methy-
lene chloride solution. A general view of 4a is depicted in Fig. 1. The
structure of 4a demonstrates some similarities to a dicyanobenzo-
furan studied recently.20 The benzofuran cycle adopts a planar
structure. The O]COCH3 substituent is coplanar to benzofuran
while the COAr group is rotated about C3eC8 bond so that
C2eC3eC8eC9 torsion angle is equal to ꢁ109.1(2)ꢀ, which is
explained by steric hindrance.
Evidently, heating intermediate 8 at 80e100 ꢀC for 1e2 h with
Et3N did not cause intramolecular nitro group displacement but
O
O
R
R
N
N
N
COOR1
COOR1
-
-
- NO2
O
O
N
N
R
O
Br
NO2
N
COOR1
4 a-d
+
NO2
-
Na+
O
O
R
N
N
1
2 a-d
H+
O
R
COOR1
OH
O
NO2
N
N
COOR1
-Na+
5 a-c
R
B
O
O
NO2
R
B
N
2' a-d
3 a-d
N
O
N
6 a-c
2, 3, 4: a – R = 4-MeC6H4, R1 = Me; b – R = 4-MeOC6H4, R1 = Me;
c – R = 2-thienyl, R1 = Me; d – R = 4-MeOC6H4, R1 = Et
5, 6: a – R = 4-MeC6H4; b – R = 4-MeOC6H4; c – R = 2-thienyl
Scheme 1.

S.I. Filimonov et al. / Tetrahedron 68 (2012) 5991e5997
5993
Table 1
Chemical shifts of H and C atoms for compounds 5a and 8a
H
5a (ppm)
8a (ppm)
C
5a (ppm)
8a (ppm)
H-3
H-6
CH2/CH
H-20/60
H-30/50
Me
8.91
8.40
5.00
7.95
7.40
2.42
8.30
9.86
7.31
7.72
7.22
2.34
C-1
C-2
C-3
C-4
C-5
C-6
CH2/CH
CeO
C-10
C-40
C-20/60
C-30/50
1-C^N
2-C^N
Me
118.7
115.1
130.1
151.1
137.0
139.2
43.1
194.0
133.1
144.7
129.5
128.4
114.9
114.6
21.3
134.1
133.1
133.6
91.2
113.7
139.0
92.3
184.7
140.6
139.6
128.6
126.8
116.8
117.6
20.9
instead resulted in nitro-nitrite rearrangement27e30 to yield nitrite
9, which, in turn, underwent cyclization to 1,2-benzoxazole 6 with
a concomitant color change of the reaction mixture from blue-
green to orange-yellow. Though aromatic nitrites like 9 are
known to undergo homolytic cleavage of the OeN bond29 under the
rearrangement conditions, in our case the nitrite function un-
dergoes intramolecular ‘trapping’ with adjacent benzyl anion to
yield 6.
Fig. 1. ORTEP view of compound 4a showing 50% probability displacement ellipsoids
and the atom-numbering scheme.
At the same time, heating of 8 in DMSO with a strong base
(MeONa, 1 equiv) at 80e100 ꢀC for 1e3 h resulted in displacement
of the nitro group to afford benzofuran 11 as a major product in
52e76% yields.
These results explain the poor yields of benzofurans 4. Thus,
interaction of the starting reagents yielded enolates 3, and hydro-
lytic cleavage of the latter afforded products 5, which were easily
converted to 1,2-benzoxazoles 6 upon treatment with the weak
bases. The latter process (formation of 1,2-benzoxazoles 6) in most
cases dominates over the formation of benzofurans 4.
The formation of 1,2-benzoxazoles 6 instead of 2,1-benzoxazoles
10 from o-nitrobenzylketones 5 is by far the most unexpected result
of this study since such transformations have never been described
in literature. At the same time, published data on aromatic nitro-
nitrite rearrangement indicate that this process is facilitated by
Fig. 2. ORTEP view of compound 6b showing 50% probability displacement ellipsoids
and the atom-numbering scheme. Only the first independent molecule (A) is shown.
R
R
O
R
O
R
O-
O
N
N
N
N
N
N
N
N
Et3N
O
+O-
N
N
NO2
NO2
O-
5 a-c
10
8
MeONa
DMF
N
N
N
N
100 oC
(Et3N)
80-100 0C
-
R
O
NO2
-
R
O-
- NO2
R
O
N
N
N
N
R
N
O
O
ONO
6 a-c
11 a-c
9
5, 6, 8, 11: a – R = 4-MeC6H4; b – R = 4-MeOC6 H4; c – R = 2-thienyl
Scheme 2.

5994
S.I. Filimonov et al. / Tetrahedron 68 (2012) 5991e5997
the presence of (1) ortho-substituents and (2) acceptor substituents
in para-position to the nitro group28,30dthat is exactly the case in
the molecules of 5. Our results show that polar solvents (like DMSO
or DMF) could facilitate this rearrangement as well.
Starting BNPN was prepared according to a known procedure.32
Alkyl 2,4-dioxobutanoates 2aed were synthesized according to
a known procedure.33
The nitro group in compounds 5 was reduced with various re-
ducing agents (method 1dwith stannous chloride in ethanolic HCl;
method 2dwith zinc in THF solution of ammonium chloride;
method 3dwith sodium dithionite in water/ethanol medium). In
all cases 1-hydroxy-2-arylindole-5,6-dicarbonitriles31 12aec were
formed selectively (Scheme 3). The best yields (76e81%) were
achieved by method 1. Side products, such as acyclic hydroxyl-
amines or amines were not observed. With sodium dithionite, the
target 1-hydroxyindole-5,6-dicarbonirtrile was obtained in anionic
form 13 which was converted to 12 upon treatment with HCl.
4.2. Alkyl 3-acyl-5,6-dicyanobenzofuran-2-carboxylates 4aed
(general procedure)
To a solution of BNPN (1.01 g, 4 mmol) in DMF (5 mL) were
added alkyl 2,4-dioxobutanoate 20aed (4 mmol) and K2CO3 (1.10 g,
8 mmol) under vigorous stirring. Stirring was continued for 6e8 h
at 60e80 ꢀC. The mixture was cooled and diluted with water
(10 mL). The resulting precipitate of benzofuran 4 was filtered off
and recrystallized from EtOH.
N
N
R
N
OH
SnCl2, H+
CH3I
12 a-c
O
R
Zn, NH4Cl
N
N
N
H+
R
NO2
N
O
Na2S2O4
N
N
5 a-c
14b
R
N
O-
+
N
Na
13 a-c
5, 12, 13, 14: a – R = 4-MeC6H4 ; b – R = 4-MeOC6H4 ; c – R = 2-thienyl
Scheme 3.
Formation of N-hydroxyindole was confirmed both by spectral
data and chemicallydby methylation of 12b with methyl iodide. An
additional signal of methoxy group (3.90 ppm) is observed in 1H
NMR spectrum of the methylation product 14b.
4.2.1. Methyl 5,6-dicyano-3-(4-methylbenzoyl)-1-benzofuran-2-
carboxylate 4a. Yield 48%, mp 207e209 ꢀC (EtOH). Mass-
spectrum (EI, 70 eV), m/z (Irel (%)): 344 [Mþ] (48.5), 329 [MþꢁMe]
(15.8), 313 [MþꢁOMe] (7.8), 285 [MþꢁCOOMe] (27.8), 119
[MeC6H4COþ] (100). IR (nmax, KBr): 2238, 1734, 1671, 1604, 1318,
897 cmꢁ1 1H NMR (DMSO-d6, J/Hz): 2.41 (s, 3H, Me), 3.72 (s, 3H,
.
3. Conclusion
OMe), 7.36 (d, J¼8.2, 2H, H(50), H(30)), 7.81 (d, J¼8.2, 2H, H(20),
H(60)), 8.56 (s, 1H, H(7)), 8.91 (s, 1H, H(4)). 13C NMR (DMSO-d6):
21.4, 53.1, 110.6, 113.2, 115.7, 115.9, 119.9, 125.1, 129.5, 129.6 (2C),
129.7 (2C), 130.0, 133.8, 145.4, 146.2, 154.1, 157.6, 187.8. Found (%): C,
69.77; H, 3.51; N, 8.14. C20H12N2O4. Calculated (%): C, 69.59; H, 3.34;
N, 8.08.
Thus, depending on the reaction conditions, reactions of 4-
bromo-5-nitrophthalonitrile (BNPN) with enolates of alkyl 4-aryl-
2,4-dioxobutanoates
dicyanobenzofuran-2-carboxylates,
nitrophthalonitriles, or 3-acyl-1,2-benzoxazole-5,6-dicarbonitriles.
Upon treatment with base, 4-(2-aryl-2-oxoethyl)-5-
could
yield
alkyl
3-acyl-5,6-
4-(2-aryl-2-oxoethyl)-5-
a
nitrophthalonitriles undergo either nitro-nitrite rearrangement
with subsequent cyclization resulting in 3-acyl-1,2-benzoxazole-
5,6-dicarbonitriles (when Et3N is used as a base) or intramolecular
nitro group displacement to afford 2-arylbenzofuran-5,6-
dicarbonitriles (when MeONa is used).
4.2.2. Methyl 5,6-dicyano-3-(4-methoxybenzoyl)-1-benzofuran-2-
carboxylate 4b. Yield 45%, mp 201e203 ꢀC (EtOH). Mass-spectrum
(EI, 70 eV), m/z (Irel (%)): 360 [Mþ], 301 [MþꢁCOOMe] (21), 253
(14), 135 [MeOC6H4COþ] (100), 107 (18), 82 (32), 77 (46), 64 (19). IR
(
nmax, KBr): 2233, 1733, 1599, 1571, 1313, 1261 cmꢁ1 1H NMR
.
(DMSO-d6, J/Hz): 3.74 (s, 3H, OMe), 3.87 (s, 3H, OMe), 7.07 (d, J¼8.9,
2H, H(50), H(30)), 7.90 (d, J¼8.9, 2H, H(20), H(60)), 8.55 (s, 1H, H(7)),
8.91 (s, 1H, H(4)). 13C NMR (DMSO-d6): 53.1, 55.8, 110.5, 113.2, 114.3
(2C), 115.7, 115.9, 119.9, 125.3, 129.2, 129.5, 130.1, 132.2 (2C), 145.9,
154.1, 157.6, 164.4, 186.4. Found (%): C, 66.51; H, 3.28; N, 7.65.
C20H12N2O5. Calculated (%): C, 66.67; H, 3.36; N, 7.77.
4. Experimental
4.1. General
NMR spectra were recorded on a Bruker-DRX500 spectrometer
(500.13 MHz for 1H,125.75 MHz for 13C) in DMSO-d6 at 30 ꢀC. Mass-
spectra were registered on a FINNIGAN MAT.INCOS 50 spectrome-
ter, ionization energy 70 eV.
The single crystal X-ray crystallographic study was carried out
with SMART APEX2 CCD diffractometer (
graphite monochromator, -scans) at 100 K.
4.2.3. Methyl 5,6-dicyano-3-(2-thienylcarbonyl)-1-benzofuran-2-
carboxylate 4c. Yield 52%, mp 210e212 ꢀC (EtOH). Mass-spectrum
(EI, 70 eV), m/z (Irel (%)): 336 [Mþ] (17.6), 253 [Mþꢁthienyl] (10.1),
111 [thienylꢁCOþ] (100). IR (nmax, KBr): 2237, 1734, 1630, 1410,
ꢀ
l
(Mo K
a
)¼0.71073 A,
u

S.I. Filimonov et al. / Tetrahedron 68 (2012) 5991e5997
5995
1315 cmꢁ1
.
1H NMR (DMSO-d6, J/Hz): 3.79 (s, 3H, OMe), 7.24 (dd,
was stirred for 10 h at 60e70 ꢀC and then for 14 h at rt. The mixture
was diluted with water (10-fold amount) and the resulting pre-
cipitate of 6 was filtered off and recrystallized from EtOH.
J¼3.9, J¼4.8, 1H, H(40)), 7.77 (br d, J¼3.9, 1H, H(30)), 8.23 (br d, J¼4.8,
1H, H(50)), 8.64 (s, 1H, H(4)), 8.91 (s, 1H, H(7)). 13C NMR (DMSO-d6):
53.2, 110.6, 113.2, 115.7, 115.9, 119.9, 124.7, 129.2, 129.4, 129.8, 137.6,
137.8,143.0,146.2,154.0,157.5,179.8. Found (%): C, 60.56; H, 2.33; N,
8.26. C17H8N2O4S. Calculated (%): C, 60.71; H, 2.40; N, 8.33.
Method B: To
nitrophthalonitrile
a
solution of 4-(2-R-2-oxoethyl)-5-
5
(2 mmol) in DMF (5 mL), Et3N (0.40 g,
4 mmol) was added and the mixture was heated at 80e100 ꢀC for
4e6 h until the initial deep-green color changed to orange-yellow.
Then the mixture was cooled and diluted with water (5 mL). The
resulting precipitate was filtered off and recrystallized from EtOH.
4.2.4. Ethyl 5,6-dicyano-3-(4-methoxybenzoyl)-1-benzofuran-2-
carboxylate 4d. Yield 46%, mp 191e193 ꢀC (EtOH). Mass-spectrum
(EI, 70 eV), m/z (Irel (%)): 374 [Mþ] (73.5), 346 [MþꢁEt] (13.8), 330
[MþꢁOEt] (81.8), 135 [MeOC6H4COþ] (93.5). IR (nmax, KBr): 2235,
1731, 1602, 1570, 1311, 1258 cmꢁ1. 1H NMR (DMSO-d6, J/Hz): 1.04 (t,
J¼7.0, 3H, Me), 3.88 (s, 3H, OMe), 4.18 (q, J¼7.0, 2H, CH2), 7.03 (d,
J¼8.8, 2H, H(50), H(30)), 7.86 (d, J¼8.8, 2H, H(20), H(60)), 8.41 (s, 1H,
H(4)), 8.83 (s, 1H, H(7)). 13C NMR (DMSO-d6): 13.4, 55.8, 62.3, 110.5,
113.1, 114.3 (2C), 115.8, 116.0, 119.9, 125.1, 129.4, 129.5, 130.2, 132.2
(2C), 146.1, 154.2, 157.1, 164.4, 186.5. Found (%): C, 67.22; H, 3.68; N,
7.34. C21H14N2O5. Calculated (%): C, 67.38; H, 3.77; N, 7.48.
4.4.1. 3-(4-Methylbenzoyl)-1,2-benzoxazole-5,6-dicarbonitrile
6a. Method B. Yield 82%, mp 221e223 ꢀC (EtOH). Mass-spectrum
(EI, 70 eV), m/z (Irel (%)): 287 [Mþ] (2.9), 140 (6,4), 119
[MeC6H4COþ] (100), 91 [MeC6H4þ] (60). IR (nmax, KBr): 2240, 1646,
1601, 1221, 886 cmꢁ1 1H NMR (DMSO-d6, J/Hz): 2.45 (s, 3H, Me),
.
7.49 (d, J¼8.2, 2H, H(50), H(30)), 8.19 (d, J¼8.2, 2H, H(20), H(60)), 8.98
(s, 1H, H(3)), 9.08 (s, 1H, H(6)). 13C NMR (DMSO-d6): 21.4, 111.2,
115.5, 115.6, 116.0, 117.8, 124.0, 129.6 (2C), 130.7 (2C), 131.4, 132.4,
146.0, 155.0, 162.7, 183.8. Found (%): C, 70.95; H, 3.09; N, 14.56.
C17H9N3O2. Calculated (%): C, 71.08; H, 3.16; N, 14.63.
4.3. 4-(2-R-2-Oxoethyl)-5-nitrophthalonitriles 5aec (general
procedure)
4.4.2. 3-(4-Methoxybenzoyl)-1,2-benzoxazole-5,6-dicarbonitrile
6b. Method B. Yield 87%, mp 215e217 ꢀC (EtOH). Mass-spectrum
(EI, 70 eV), m/z (Irel (%)): 303 [Mþ] (10), 169 (5), 135
[OMeC6H4COþ] (100), 107 [C6H4COþ] (11.7), 92 (23.9), 89 (23.8), 77
(43.7), 64 (77), 43 (34). IR (nmax, KBr): 2237, 1605, 1590, 1281,
To a solution of BNPN (1.01 g, 4 mmol) in DMF (5 mL), sodium
enolates of alkyl 2,4-dioxobutanoates 2aed (8 mmol) were added
under vigorous stirring. Stirring was continued for 18e24 h at rt.
The mixture was diluted with 5% aqueous HCl water (10-fold ex-
cess). The resulting crystalline precipitate of 5 was filtered off and
recrystallized from EtOH.
1226 cmꢁ1 1H NMR (DMSO-d6, J/Hz): 3.91 (s, 3H, OMe), 7.19 (d,
.
J¼8.9, 2H, H(50), H(30)), 8.26 (d, J¼8.9, 2H, H(20), H(60)), 8.89 (s, 1H,
H(3)), 8.99 (s, 1H, H(6)). 13C NMR (DMSO-d6): 55.8, 110.9, 114.4 (2C),
115.4, 115.4, 115.9, 117.7, 123.9, 127.5, 131.3, 133.0 (2C), 154.9, 162.5,
164.7, 182.2. Found (%): C, 67.28; H, 2.90; N, 13.81. C17H9N3O3. Cal-
culated (%): C, 67.33; H, 2.99; N, 13.86.
4.3.1. 4-[2-(4-Methylphenyl)-2-oxoethyl]-5-nitrophthalonitrile
5a. Yield 68%, mp 159e160 ꢀC (EtOH). Mass-spectrum (EI, 70 eV),
m/z (Irel (%)): 305 [Mþ] (0.4), 257 (1.2), 215 (3.7), 119 [MeC6H4COþ]
(100), 91 [MeC6Hþ4 ] (43). IR (nmax, KBr): 2243, 1680, 1605, 1526,
1331 cmꢁ1. 1H NMR (DMSO-d6, J/Hz): 2.42 (s, 3H, Me), 5.00 (s, 2H,
CH2), 7.41 (d, J¼8.2, 2H, H(50), H(30)), 7.96 (d, J¼8.2, 2H, H(20), H(60)),
8.41 (s, 1H, H(3)), 8.92 (s, 1H, H(6)). For 13C NMR see Table 1. Found
(%): C, 66.72; H, 3.54; N, 13.68. C17H11N3O3. Calculated (%): C, 66.88;
H, 3.63; N, 13.76.
4.4.3. 3-(2-Thienylcarbonyl)-1,2-benzoxazole-5,6-dicarbonitrile
6c. Method B. Yield 81%, mp 225e227 ꢀC (EtOH). Mass-spectrum
(EI, 70 eV), m/z (Irel (%)): 279 [Mþ] (3.8), 113 (5.9), 112 (6.3), 111
[C4H3S-COþ] (100). IR (nmax, KBr): 2238, 1624, 1410, 1406, 836,
760 cmꢁ1
.
1H NMR (DMSO-d6, J/Hz): 7.38 (dd, J¼3.7, J¼5.0, 1H,
H(40)), 8.32 (d, J¼5.0,1H, H(50)), 8.42 (d, J¼3.7, 1H, H(30)), 8.91 (s, 1H,
H(3)), 9.01 (s, 1H, H(6)). 13C NMR (DMSO-d6): 111.4, 115.4, 115.5,
116.1, 117.9, 123.5, 127.6, 131.3, 137.8, 138.9, 140.3, 154.6, 162.8, 175.5.
Found (%): C, 60.05; H, 1.72; N, 14.96. C14H5N3O2S. Calculated (%): C,
60.21; H, 1.80; N, 15.05.
4.3.2. 4-[2-(4-Methoxyphenyl)-2-oxoethyl]-5-nitrophthalonitrile
5b. Yield 74%, mp 175e177 ꢀC (EtOH). Mass-spectrum (EI, 70 eV),
m/z (Irel (%)): 321 [Mþ] (11), 303 [MþꢁH2O] (5), 231(1.2), 135
[MeOC6H4COþ] (100), 107, 92, 77, 64. IR (nmax, KBr): 2243, 1673,
1595,1530,1345,1220, 1165 cmꢁ1. 1H NMR (DMSO-d6, J/Hz): 3.88 (s,
3H, OMe), 4.97 (s, 2H, CH2), 7.12 (d, J¼8.9, 2H, H(50), H(30)), 8.04 (d,
J¼8.9, 2H, H(20), H(60)), 8.40 (s, 1H, H(3)), 8.91 (s, 1H, H(6)). 13C NMR
(DMSO-d6): 42.7, 55.2, 114.1 (2C), 114.5, 114.8, 114.9, 118.5, 128.3,
129.9, 130.6 (2C), 137.0, 139.1, 151.1, 163.7, 192.6. Found (%): C, 63.36;
H, 3.38; N, 13.02. C17H11N3O4. Calculated (%): C, 63.55; H, 3.45; N,
13.08.
4.5. 2-R-Benzofuran-5,6-dicarbonitriles 11aec (general
procedure)
To a solution of 5aec (1 mmol) in DMSO (3 mL) were added Et3N
(0.20 g, 2 mmol) and MeONa (55 mg, 1 mmol) (in that order), and
the mixture was heated at 80e100 ꢀC for 1e2 h until the color of
the solution changed from deep-blue to brown. After cooling, water
(3e5 mL) was added, the resulting precipitate was filtered off and
recrystallized from EtOH.
4.3.3. 4-Nitro-5-[2-oxo-2-(2-thienyl)ethyl]phthalonitrile 5c. Yield
72%, mp 158e161 ꢀC (EtOH). Mass-spectrum (EI, 70 eV), m/z (Irel
(%)): 297 [Mþ] (2.1), 279 [MþꢁH2O] (9), 111 [C4H3SꢁCO] (100), 39
(28). IR (nmax, KBr): 2237, 1658, 1671, 1527, 1410, 1342 cmꢁ1. 1H NMR
(DMSO-d6, J/Hz): 4.96 (s, 2H, CH2), 7.30 (dd, J¼3.7, J¼5.0, 1H, H(40)),
8.11 (d, J¼5.0, 1H, H(50)), 8.17 (d, J¼3.7, 1H, H(30)), 8.41 (s, 1H, H(3)),
8.80 (s, 1H, H(6)). 13C NMR (DMSO-d6): 43.8, 114.4, 114.7, 115.2,
118.6, 128.9, 130.0, 134.4, 135.9, 136.0, 139.1, 142.0, 150.9, 187.2.
Found (%): C, 56.42; H, 2.32; N, 14.08. C14H7N3O3S. Calculated (%): C,
56.56; H, 2.37; N, 14.13.
4.5.1. 2-(4-Methylphenyl)-1-benzofuran-5,6-dicarbonitrile
11a. Yield 64%, mp 243e244 ꢀC. Mass-spectrum (EI, 70 eV), m/z (Irel
(%)): 258 [Mþ] (100), 129, 115. IR (nmax, KBr): 2230, 1585, 1505, 1468,
1307, 807 cmꢁ1. 1H NMR (DMSO-d6, J/Hz): 2.39 (s, 3H, Me), 7.34 (d,
J¼8.1, 2H, H(30), H(50)), 7.54 (s, 1H, H(3)), 7.84 (d, J¼8.1, 2H, H(20),
H(60)), 8.39 (s, 1H, H(7)), 8.43 (s, 1H, H(4)). 13C NMR (DMSO-d6):
21.0, 101.6, 108.8, 109.4, 116.4, 116.5, 117.5, 125.3, 125.6 (2C), 127.7,
129.8 (2C), 133.6, 140.7, 154.4, 161.2. Found (%): C, 79.00; H, 3.82; N,
10.82. C17H10N2O. Calculated (%): C, 79.06; H, 3.90; N, 10.85.
4.4. 3-Acyl-1,2-benzoxazole-5,6-dicarbonitriles 6aec
Method A. A solution of BNPN (1.01 g, 4 mmol) and sodium
enolate of alkyl 2,4-dioxobutanoates 2aed (8 mmol) in DMF (5 mL)
4.5.2. 2-(4-Methoxyphenyl)-1-benzofuran-5,6-dicarbonitrile
11b. Yield 60%, mp 248e249 ꢀC. Mass-spectrum (EI, 70 eV), m/z (Irel

5996
S.I. Filimonov et al. / Tetrahedron 68 (2012) 5991e5997
(%)): 274 [Mþ] (100). IR (nmax, KBr): 2231, 1583, 1505, 1470,
1175 cmꢁ1 1H NMR (DMSO-d6, J/Hz): 3.84 (s, 3H, OMe), 7.11 (d,
(EI, 70 eV), m/z (Irel (%)): 265 [Mþ] (40), 248 [MþꢁOH] (100), 204
.
(69), 139 (47), 124 (37), 11 (46), 88 (27), 69 (46), 45 (85). IR (nmax,
J¼8.8, 2H, H(30), H(50)), 7.52 (s, 1H, H(3)), 7.92 (d, J¼8.8, 2H, H(20),
H(60)), 8.43 (s, 1H, H(7)), 8.50 (s, 1H, H(4)). 13C NMR (DMSO-d6):
54.4, 100.5, 108.3, 109.2, 114.7 (2C), 116.5, 116.6, 117.3, 120.3, 127.3
(2C), 127.4, 133.7, 154.2, 161.0, 161.1. Found (%): C, 74.38; H, 3.67; N,
10.15. C17H10N2O2. Calculated (%): C, 74.45; H, 3.67; N, 10.21.
KBr): 3250e3100 (br), 2229, 1478, 711 cmꢁ1. 1H NMR (DMSO-d6, J/
Hz): 7.07 (s, 1H, H(3)), 7.27 (dd, J¼3.8, J¼4.9, 1H, H(40)), 7.81 (d,
J¼4.9, 1H, H(50)), 7.91 (d, J¼3.9, 1H, H(30)), 8.21 (s, 1H, H(6)), 8.34 (s,
1H, H(6)), 12.46 (s, 1H, OH). 13C NMR (DMSO-d6): 96.3, 104.1, 104.6,
115.4, 117.4, 117.5, 124.8, 127.5, 128.0, 128.5, 129.2, 129.4, 133.6, 137.0.
Found (%): C, 63.19; H, 2.54; N, 15.82. C14H7N3OS. Calculated (%): C,
63.38; H, 2.66; N, 15.84.
4.5.3. 2-(2-Thienyl)-1-benzofuran-5,6-dicarbonitrile 11c. Yield 46%,
mp 238e239 ꢀC. Mass-spectrum (EI, 70 eV), m/z (Irel (%)): 250 [Mþ]
(55), 83 [C4H3Sþ] (100). IR (nmax, KBr): 2230, 1586, 1502, 1465,
1315 cmꢁ1. 1H NMR (DMSO-d6, J/Hz): 7.28 (dd, J¼3.7, 4.9, 1H, H(40)),
7.51 (s, 1H, H(3)), 7.86 (d, J¼3.7, 1H, H(30)), 7.87 (d, J¼4.9, 1H, H(50)),
8.46 (s, 1H, H(7)), 8.56 (s, 1H, H(4)). 13C NMR (DMSO-d6): 101.4,
108.8, 109.6, 116.4, 116.5, 117.5, 127.6, 128.3, 128.9, 130.0 (2C), 133.5,
154.0, 156.2. Found (%): C, 66.98; H, 2.37; N, 11.15. C14H6N2OS.
Calculated (%): C, 67.19; H, 2.42; N, 11.19.
4.7. 1-Methoxy-2-(4-methoxyphenyl)-1H-indole-5,6-
dicarbonitrile 14b
To a solution of 1-hydroxyindole 12b (0.29 g, 1 mmol) in DMF
(5 mL) were added MeI (0.21 g, 1.5 mmol) and K2CO3 (0.28 g,
2 mmol), and the mixture was stirred at 40e50 ꢀC for 1e2 h,
cooled, diluted with water (5 mL), the resulting precipitate was
filtered off and recrystallized from EtOH. Yield 82%, mp 184e186 ꢀC
(EtOH). Mass-spectrum (EI, 70 eV), m/z (Irel (%)): 303 [Mþ] (79), 288
[MþꢁMe] (9), 272 [MþꢁOMe] (100), 257 (12), 245 (24), 228 (27),
202 (21), 176 (7), 152 (8), 136 (8), 115 (6), 63 (7). IR (nmax, KBr): 2228,
1607, 1490, 1265, 827 cmꢁ1. 1H NMR (DMSO-d6, J/Hz): 3.85 (s, 3H,
OMe), 3.91 (s, 3H, OMe), 6.99 (s, 1H, H(3)), 7.14 (d, J¼8.9, 2H, H(50),
H(30)), 7.90 (d, J¼8.9, 2H, H(20), H(60)), 8.38 (s, 1H, H(3)), 8.43 (s, 1H,
H(6)). 13C NMR (DMSO-d6): 55.3, 66.1, 98.3, 104.8, 105.2, 114.6 (2C),
115.5, 115.6, 117.3, 120.2, 125.2, 127.5, 129.2 (2C), 132.2, 140.7, 160.3.
Found (%): C, 71.11; H, 4.26; N, 3.82. C18H13N3O2. Calculated (%): C,
71.28; H, 4.32; N, 3.85.
4.6. 2-R-1-Hydroxy-1H-indole-5,6-dicarbonitriles 12aec
Method A. To a solution of stannous chloride (1.90 g, 0.01 mol) in
concd HCl (2 mL) and EtOH (2 mL), 4-(2-R-2-oxoethyl)-5-
nitrophthalonitrile 5 (3 mmol) was added, and the mixture was
stirred at 50 ꢀC for 0.5e1 h. The precipitate formed upon cooling of
the solution was filtered off and recrystallized from EtOH.
Method B. To a solution of 4-(2-R-2-oxoethyl)-5-nitrophthalonitrile
5 (1 mmol) in THF (5 mL), aqueous solution of ammonium chloride
(0.11 g, 2 mmol in 1 mL of water) and zinc dust (0.20 g, 3 mmol) were
added. The reaction mixture was stirred at 40e50 ꢀC for 1e2 h until
the green color of the solution disappeared. Then unreacted zinc was
removed by filtration, the filtrate poured into water (10 mL), and the
precipitate was filtered off and recrystallized from EtOH.
Method C. To a suspension of 4-(2-R-2-oxoethyl)-5-nitrophth-
alonitrile 5 (1 mmol) in EtOH (10 mL), a solution of sodium
hydrosulfite (0.52 g, 3 mmol) in 5 mL of water was added, and the
resulting mixture was heated at 40e50 ꢀC for 1e2 h until the green
color of the solution disappeared. The suspension was cooled, the
resulting precipitate filtered off, stirred with 5 mL of 50% aqueous
EtOH containing concd HCl (0.5 mL), and recrystallized from EtOH.
References and notes
1. Terrier, F. Nucleophilic Aromatic Displacement: the Influence of the Nitro Group;
VSH: New York, NY, 1991; 460 p.
2. Radl, S. Adv. Heterocycl. Chem. 2002, 83, 189e257.
3. Rusanov, A. L.; Komarova, L. G.; Likhatchev, D. Yu.; Shevelev, S. A.; Tartakovsky,
V. A. Russ. Chem. Rev. 2003, 72, 899e911.
4. Cartwright, M. W.; Parks, E. L.; Pattison, G.; Slater, R.; Sandford, G.; Wilson, I.;
Yufit, D. S.; Howard, J. A. K.; Christopher, J. A.; Miller, D. D. Tetrahedron 2010, 66,
3222e3227.
5. Lu, B.; Wang, B.; Zhang, Y.; Ma, D. J. Org. Chem. 2007, 72, 5337e5341.
6. Filimonov, S. I.; Chirkova, Zh. V.; Abramov, I. G.; Shashkov, A. S.; Firgang, S. I.;
Stashina, G. A. Mendeleev Commun. 2009, 19, 332e333.
7. Dann, O.; Char, H.; Grießmeier, H. Liebigs Ann. Chem. 1982, 1836e1869.
8. Hu, J.; Wu, L.-Y.; Wang, X.-C.; Hu, Y.-Y.; Niu, Y.-N.; Liu, X.-Y.; Yang, S.; Liang, Y.-M.
Adv. Synth. Catal. 2010, 352, 351e356.
9. Ono, S.; Inoue, Y.; Yoshida, T.; Maeda, K.; Kosaka, K.; Imada, T.; Fukaya, C.;
Nakamura, N. Chem. Pharm. Bull. 1999, 47, 1694e1712.
10. Sall, D. J.; Arfsten, A. E.; Bastian, J. A.; Denney, M. L.; Harms, C. S.; McCowan, J.
R.; Morin, J. M.; Rose, J. W.; Scarborough, R. M.; Smyth, M. S.; Um, S. L.; Ut-
terback, B. G.; Vasileff, R. T.; Wikel, J. H.; Wyss, V. L.; Jakubowski, J. A. J. Med.
Chem. 1997, 40, 2843e2857.
11. Li, J.; Rush, Th. S.; Li, W.; DeVincentis, D.; Du, X.; Hu, Y.; Thomason, J. R.; Xiang,
J. S.; Skotnicki, J. S.; Tam, S.; Cunningham, K. M.; Chockalingam, P. S.; Morris, E.
A.; Levin, J. I. Bioorg. Med. Chem. Lett. 2005, 15, 4961e4966.
12. Abramov, I. G.; Smirnov, A. V.; Ivanovskii, S. A.; Abramova, M. B.; Plakhtinskii,
V. V. Heterocycles 2001, 55, 1161e1163.
4.6.1. 1-Hydroxy-2-(4-methylphenyl)-1H-indole-5,6-dicarbonitrile
12a. Method A. Yield 76%, mp 197e199 ꢀC (EtOH). Mass-spectrum
(EI, 70 eV), m/z (Irel (%)): 273 [Mþ] (100), 256 [MþꢁOH] (23). IR
(
nmax, KBr): 3550e3400 (br), 2227, 1490, 1342, 819 cmꢁ1 1H NMR
.
(DMSO-d6, J/Hz): 2.37 (s, 3H, Me), 6.97 (s, 1H, H(3)), 7.37(d, J¼8.2,
2H, H(50), H(30)), 7.87 (d, J¼8.2, 2H, H(20), H(60)), 8.25 (s, 1H, H(4)),
8.36 (s, 1H, H(7)), 12.11 (s, 1H, OH). 13C NMR (DMSO-d6): 20.8, 97.8,
103.7, 104.6, 115.6, 117.4, 117.6, 124.5, 125.9, 127.6, 128.1 (2C), 127.4
(2C), 134.1, 139.0, 142.3. Found (%): C, 74.62; H, 3.98; N, 15.32.
C17H11N3O. Calculated (%): C, 74.71; H, 4.06; N, 15.38.
13. Abramov, I. G.; Smirnov, A. V.; Ivanovskii, S. A.; Abramova, M. B.; Plakhtinskii,
V. V.; Belysheva, M. S. Mendeleev Commun. 2001, 11, 80e81.
14. Filimonov, S. I.; Chirkova, Zh. V.; Abramov, I. G.; Firgang, S. I.; Stashina, G. A.;
Suponitsky, K. Yu Heterocycles 2011, 83, 755e763.
15. Sharman, W. M.; van Lier, J. E. In Porphyrin Handbook; Kadish, K. M., Smith, K. M.
, Guilard, R., Eds.; Elsevier Science: USA, 2003; Vol. 15, pp 1e60.
16. Artamkina, G. A.; Beletskaya, I. P. Russ. Chem. Rev. 1987, 56, 983e1001.
17. Bray, D. J.; Jolliffe, K. A.; Lindoy, L. F.; McMurtrie, J. C. Tetrahedron 2007, 63,
1953e1958.
4.6.2. 1-Hydroxy-2-(4-methoxyphenyl)-1H-indole-5,6-dicarbonitrile
12b. Method A. Yield 81%, mp 204e206 ꢀC (EtOH). Mass-spectrum
(EI, 70 eV), m/z (Irel (%)): 289 [Mþ] (39), 273 [MþꢁO] (74), 272
[MþꢁOH] (73), 258 [MþꢁOMe] (100), 245 (25), 230 (34), 202 (19),
77 (69), 51 (47), 44 (60). IR (nmax, KBr): 3500e3300 (br), 2222, 2237,
1490, 1254, 1180 cmꢁ1. 1H NMR (DMSO-d6, J/Hz): 3.84 (s, 3H, OMe),
6.91 (s, 1H, H(3)), 7.12 (d, J¼8.9, 2H, H(50), H(30)), 7.92 (d, J¼8.9, 2H,
H(20), H(60)), 8.22 (s, 1H, H(3)), 8.33 (s, 1H, H(6)), 12.10 (s, 1H, OH).
13C NMR (DMSO-d6): 55.4, 97.3, 103.8, 104.4, 114.4 (2C), 115.6, 117.6,
117.7, 121.1, 124.7, 127.4, 129.8 (2C), 134.1, 142.3, 160.1. Found (%): C,
70.46; H, 3.75; N, 14.48. C17H11N3O2. Calculated (%): C, 70.58; H,
3.83; N, 14.52.
18. Zeevaart, J. G.; Parkinson, C. J.; Koning, C. B. Tetrahedron Lett. 2007, 48,
3289e3293.
19. Crystallographic data for 4a: C20H12N2O4, triclinic, space group P-1: a¼6.
ꢀ
ꢀ
ꢀ
7222(5) A, b¼8.3646(7) A, c¼14.5905(12) A,
a
¼101.6360(10)ꢀ,
b
¼92.353(2)ꢀ,
3
ꢀ
g
¼91.182(2)ꢀ, V¼802.51(11) A , Z¼2, M¼344.32, dcalcd¼1.425 g/cm3, wR2¼0.
1140, GOF¼1.036 for 4217 independent reflections with 2
q
<58ꢀ, R1¼0.0422 for
3413 reflections with I>2s(I). Crystallographic data (excluding structure fac-
tors) have been deposited at the Cambridge Crystallographic Data Centre
(CCDC) as supplementary publication no. CCDC 855324.
4.6.3. 1-Hydroxy-2-(2-thienyl)-1H-indole-5,6-dicarbonitrile
12c. Method A. Yield 79%, mp 215e217 ꢀC (EtOH). Mass-spectrum
20. Filimonov, S. I.; Chirkova, Zh. V.; Abramov, I. G.; Firgang, S. I.; Stashina, G. A.;
Suponitsky, K. Yu Mendeleev Commun. 2011, 21, 46e47.

S.I. Filimonov et al. / Tetrahedron 68 (2012) 5991e5997
5997
21. Kovalenko, S. V.; Artamkina, G. A.; Terent’ev, P. B.; Shevtsov, V. K.; Beletskaya, I.
P.; Reutov, O. A. Chem. Heterocycl. Compd. 1990, 26, 357e361.
26. Olson, E. J.; Xiong, T. T.; Cramer, C. J.; Buhlmann, P. J. Am. Chem. Soc. 2011, 133,
12858e12865.
22. Wunsch, K. H.; Boulton, A. J. Adv. Heterocycl. Chem. 1967, 8, 277e379.
27. Korolev, V. L.; Pivina, T. S.; Porollo, A. A.; Petukhova, T. V.; Sheremetev, A. B.;
23. Crystallographic data for 6b: C17H9N3O3, monoclinic, space group P21/c: a¼16.
Ivshin, V. P. Russ. Chem. Rev. 2009, 78, 945e969.
28. Khrapkovskii, G. M.; Shamov, A. G.; Nikolaeva, E. V.; Chachkov, D. V. Russ. Chem.
Rev. 2009, 78, 903e942.
29. Cohen, R.; Zeiri, Y.; Wurzberg, E.; Kosloff, R. J. Phys. Chem. A 2007,111,11074e11083.
30. Fayet, G.; Joubert, L.; Rotureau, P.; Adamo, C. J. Phys. Chem. A 2008, 112,
4054e4059.
3
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
061(6) A, b¼25.068(10) A, c¼6.885(3) A,
b
¼99.621(7) , V¼2732.8(18) A , Z¼8,
M¼303.27, dcalcd¼1.474 g/cm3, wR2¼0.1957, GOF¼1.046 for 5365 independent
reflections with 2
q
<52ꢀ, R1¼0.0824 for 2565 reflections with I>2
s
(I). Crystal-
lographic data (excluding structure factors) have been deposited at the Cam-
bridge Crystallographic Data Centre (CCDC) as supplementary publication no.
CCDC 855325.
31. Nicolaou, K. C.; Estrada, A. A.; Freestone, G. C.; Lee, S. H.; Alvarez-Mico, X.
24. Snyder, S. E.; Carey, J. R.; Shvets, A. B.; Pirkle, W. H. J. Org. Chem. 2005, 70,
4073e4081.
25. Gololobov, Yu. G.; Gol’ding, I. R.; Terrier, F.; Petrovskii, P. V.; Lyssenko, K. A.;
Garbuzova, I. A. Russ. Chem. Bull. 2009, 58, 2443e2448.
Tetrahedron 2007, 63, 6088e6114.
32. Ivanovskii, S. A.; Dorogov, M. V.; Abramov, I. G.; Smirnov, A. V. Russian Patent
2167855, 2001.
33. Maurin, C.; Bailly, F.; Cotelle, P. Tetrahedron 2004, 60, 6479e6486.