Microwave assisted synthesis of 3-aminoindole-2-carbonitriles from anthranilonitriles via N-unprotected 2-(cyanomethylamino)benzonitriles

Article abstract of DOI:10.1016/j.tet.2009.11.067

Anthranilonitrile 3a, 4,5-dimethoxyanthranilonitrile 3b and 5-nitroanthranilonitrile 3c, react with paraformaldehyde, KCN and ZnCl₂ in acetic acid under acid catalysis (H₂SO₄) in a sealed tube at ca. 55 °C to give the corresponding 2-(cyanomethylamino)benzonitriles 4a-c in 96, 86 and 57% yields, respectively. Thorpe-Ziegler cyclisation of the N-unprotected 2-(cyanomethylamino)benzonitriles 4a-c with K₂CO₃ in EtOH at elevated temperatures and pressures using either microwave heating or conventional heating in a sealed tube gives 3-amino, 3-amino-5,6-dimethoxy, and 3-amino-5-nitroindole-2-carbonitriles 2a-c in moderate to good yields. All new compounds are fully characterised.

Full text of DOI:10.1016/j.tet.2009.11.067

Tetrahedron 66 (2010) 685–688
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Microwave assisted synthesis of 3-aminoindole-2-carbonitriles from
anthranilonitriles via N-unprotected 2-(cyanomethylamino)benzonitriles
*
Sophia S. Michaelidou, Panayiotis A. Koutentis
Department of Chemistry, University of Cyprus, PO Box 20537, 1678 Nicosia, Cyprus
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 August 2009
Received in revised form 26 October 2009
Accepted 12 November 2009
Available online 17 November 2009
Anthranilonitrile 3a, 4,5-dimethoxyanthranilonitrile 3b and 5-nitroanthranilonitrile 3c, react with
paraformaldehyde, KCN and ZnCl2 in acetic acid under acid catalysis (H2SO4) in a sealed tube at ca. 55 ꢀ
C
to give the corresponding 2-(cyanomethylamino)benzonitriles 4a–c in 96, 86 and 57% yields, re-
spectively. Thorpe–Ziegler cyclisation of the N-unprotected 2-(cyanomethylamino)benzonitriles 4a–c
with K2CO3 in EtOH at elevated temperatures and pressures using either microwave heating or con-
ventional heating in a sealed tube gives 3-amino, 3-amino-5,6-dimethoxy, and 3-amino-5-nitro-
indole-2-carbonitriles 2a–c in moderate to good yields. All new compounds are fully characterised.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
tosylindole-2-carbonitrile via a three-step synthesis.5 While the
second provided 3-(N-anilino)indole-2-carbonitriles via dehydrating
Many indoles are important in both the biological and material
sciences.1 More specifically, several substituted 2-cyanoindoles are
important intermediates in the synthesis of heteroaromatic mole-
cules and biologically active compounds.2,3 We recently discovered
a new route to 3-aminoindole-2-carbonitriles 2 starting from 2-
or elimination steps to introduce the cyano functionality at C-2.6 3-
Aminoindole-2-carbonitriles have been used as building blocks for
pyrido[3,2-b]indoles
(d
-carbolines),6 and for pyrimido[5,4-b]in-
doles.7 Interestingly, the isomeric 2-aminoindole-3-carbonitriles are
more readily available,8–11 and have found uses as scaffolds for the
construction of pyrimido[1,2-a]indoles,12 and pyrimido[4,5-b]in-
doles.9,13–15
(4-chloro-1,2,3-dithiazolylidenamino)benzonitriles
1 on reaction
with triphenylphosphine.4 This transformation however, did not
tolerate methoxysubstitution on the arene ring and specifically failed
to provide access to 3-amino-5,6-dimethoxyindole-2-carbonitrile.
Furthermore, it was stated that N-protection of the 2-(cyano-
methylamino)benzonitrile was necessary for the Thorpe–Ziegler
cyclisation to work.5 Similar Thorpe–Ziegler cyclisations of (Z)-3-
(cyanomethylamino)acrylonitriles to afford 3-aminopyrrole-2-
carbonitriles also required protection of the amino group since the
anion formed by the base abstraction of the NH proton would be
more stable than its methylene analogue.16,17
CN
NH2
PPh3, H2O
N
Cl
CN
N
R
R
S
N
H
S
CN
CN
N
CN
1
2
Base
N
H
CN
CN
N
H
CN
As such, we decided to develop a rational route to 3-aminoindole-
2-carbonitriles 2 that would tolerate both electron withdrawing and
donating substituents on the arene ring. To date there are only two
routes to 3-aminoindole-2-carbonitriles: The first involved N-tosy-
lation of the anthranilonitrile, followed by cyanomethylation to af-
ford 2-[N-(cyanomethyl)-N-tosylamino]benzonitrile, which can then
suffer base catalysed Thorpe–Ziegler cyclisation to give 3-amino-1-
Both N-methylation using diazomethane,18,19 bromomethane20
and N-carboalkoxylation using benzyl,21 methyl22 or ethyl chloro-
formate17,23–28 have been used to enhance the formation of the re-
quired carbanion intermediate in the cyclisation to afford pyrroles.
Owing to difficulties encountered during the detosylation of 3-
amino-1-tosylindole-2-carbonitrile,29 we considered the alternative
cyclisation of N-unprotected 2-(cyanomethylamino)benzonitrile 4a
rather than replace the tosyl protecting group.
* Corresponding author. Tel.: þ00357 22 892783; fax: þ00357 22 892809.
E-mail address: koutenti@ucy.ac.cy (P.A. Koutentis).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.11.067

686
S.S. Michaelidou, P.A. Koutentis / Tetrahedron 66 (2010) 685–688
Table 2
2. Results and discussion
Transformation of 2-(cyanomethylamino)benzonitriles 4a–c into 3-aminoindole-
2-carbonitriles 2a–c in EtOH (1 mL)
2.1. N-Unprotected Thorpe–Ziegler cyclisation
NH2
R
R
CN
Direct cyanomethylation of 2-aminobenzonitriles 3a–c using
chloroacetonitrile could not readily be achieved, however, an al-
ternative route that made use of paraformaldehyde, KCN and zinc
chloride in acetic acid catalysed by H2SO4 worked well.30 A partial
optimisation indicated that performing the reaction in a sealed
tube allowed the use of fewer equivalents of reagents, in particular
for the more electron rich aminobenzonitriles 3a and 3b, however
2-amino-5-nitrobenzonitrile 3c required the use of excess reagents
(Table 1).
K2CO3
EtOH
CN
N
N
H
CN
H
4a-c
2a-c
R (4a–c)
K2CO3 (equiv)
Temp (ꢀC)
Time (min)
Yields (%)
H
H
H
1
120a
120a
120a
120a
120a
140b
180b
140b
180b
140b
180b
5
8
20
45
5
90
25
90
66
60
15
2a (60)
2a (78)
2a (71)
2b (88)
2c (87)
2a (57)
2a (55)
2b (88)
2b (66)c
2c (37)
2c (56)
0.5
0.1
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
4,5-(MeO)2
5-NO2
H
Table 1
Reaction of 2-aminobenzonitriles 3a–c with paraformaldehyde, KCN, ZnCl2, and
catalytic H2SO4 (cat.) in AcOH
H
4,5-(MeO)2
4,5-(MeO)2
5-NO2
5-NO2
R
R
CN
CN
AcOH
+
(CH2O)n
+
+ ZnCl2
KCN
H2SO4 (cat.)
NH2
N
H
CN
a
MW 250 W, 180 PSI (max).
Sealed tube in preheated Wood’s metal bath.
2-Amino-5-nitrobenzonitrile 3c was also isolated in 25% yield.
b
c
3a-c
4a-c
R
(CH2O)n KCN
ZnCl2
Tempa (ꢀC) Time (h) Yields (%)
(equiv)
(equiv) (equiv)
H
H
H
H
3
3
8
4
2
1.1
4
2
8
10
10
55
25
3 min
6
3
48
2
1
48
48
11
4a (85)
4a (97)
4a (96)
IRc
3. Conclusions
1.5
1.1
1.1
1.5
1.1
1.1
1.5
1.1
3
55b
25–55b
25
3-Aminoindole-2-carbonitriles 2a–c supporting either NO2 and
MeO substituents on the arene were prepared from anthraniloni-
triles via the N-unprotected Thorpe–Ziegler cyclisation of the
2-(cyanomethylamino)benzonitriles 4a–c at elevated temperatures
and pressures, in two steps in best overall yields of 75, 76 and 50%,
respectively.
4,5-(MeO)2 1.5
4,5-(MeO)2 1.1
5-NO2
5-NO2
5-NO2
4b (83)
4b (86)
IRc
55b
55b
55
3
5
5
5
5
IRc
55b
4c (57)
a
Preheated oil bath temperature.
The reaction took place in a sealed tube.
IR¼Incomplete reaction.
b
c
4. Experimental
The attempted cyclisation of 2-(cyanomethylamino)benzoni-
4.1. General methods and materials
trile 4a into 3-aminoindole-2-carbonitrile 2a in EtOH at room
temperature using a variety of bases (2 equiv) (K2CO3, Cs2CO3,
NaOH, DBU) gave no reaction while at 60 ꢀC complex mixtures
were obtained. Nevertheless, repeating the reaction using K2CO3
(2 equiv) in EtOH, DMF or DMSO and heating in a CEM microwave
reactor at ca. 120 ꢀC at 180, 80 and 50 PSI, respectively gave the
desired 3-aminoindole-2-carbonitrile 2a in moderate yields (38–
50%). Of the solvents screened, EtOH gave the highest product
yields (50%) and the fastest reaction times (5 min), presumably
due to the higher reaction vessel pressures. As such, EtOH was
selected as the solvent for further optimisations. Indeed, in EtOH
the reactions proceeded readily using only a catalytic amount of
K2CO3 (0.5 equiv). Furthermore, by using a sealed tube and pre-
heated Wood’s metal baths the cyclisations could be achieved
using conventional heating (hot plate stirrers), although product
yields were somewhat lower and the reaction times longer
(Table 2).
The observed differences between the microwave and the
conventional heating were tentatively ascribed to the difficulty in
accurately recording the internal temperature and pressure of the
reactions performed in the microwave reactor using only the
available external temperature and pressure probes. Nevertheless,
at these elevated temperatures and pressures the formation of
sufficient quantities of the required cyanomethylene carbanion
allowed the desired Thorpe–Ziegler cyclisation to proceed without
the need for N-protection. Thus allowing a rapid two-step synthesis
of 3-aminoindole-2-carbonitriles 2a–c that tolerates both electron
withdrawing NO2 and electron releasing MeO substituents on the
benzo ring.
Reactions were protected from atmospheric moisture by CaCl2
drying tubes. Anhydrous Na2SO4 was used for drying organic ex-
tracts, and all volatiles were removed under reduced pressure. All
reaction mixtures and column eluents were monitored by TLC us-
ing commercial glass backed thin layer chromatography (TLC)
plates (Merck Kieselgel 60 F254). The plates were observed under
UV light at 254 and 365 nm. The technique of dry flash
chromatography was used throughout for all non-TLC scale chro-
matographic separations using Merck Silica Gel 60 (less than
0.063 mm).31 A CEM Discover Microwave Reactor was used for
microwave experiments. Chemglass heavy wall cylindrical pressure
vessels (15 mL) with a Teflon bushing as a pressure seal were used
for the sealed tube studies. Melting points were determined using
a PolyTherm-A, Wagner & Munz, Koefler–Hotstage Microscope
apparatus. Solvents used for recrystallisation are indicated after the
melting point. UV spectra were obtained using a Perkin–Elmer
Lambda-25 UV/vis spectrophotometer and inflections are identi-
fied by the abbreviation ‘inf’. IR spectra were recorded on a Shi-
madzu FTIR-NIR Prestige-21 spectrometer with a Pike Miracle Ge
ATR accessory and strong, medium and weak peaks are represented
by s, m and w, respectively. 1H and 13C NMR spectra were recorded
on a Bruker Avance 300 machine (at 300 and 75 MHz, respectively).
13C DEPT NMR was used to identify quaternary and tertiary carbons,
which are indicated by (s) and (d) notations, respectively. Deuter-
ated solvents were used for homonuclear lock and the signals are
referenced to the deuterated solvent peaks. Low resolution (EI)
mass spectra were recorded on a Shimadzu Q2010 GC–MS with
direct inlet probe.

S.S. Michaelidou, P.A. Koutentis / Tetrahedron 66 (2010) 685–688
687
4.1.1. 2-(Cyanomethylamino)benzonitrile 4a: (Typical procedure, see
Table 1). To a stirred solution of 2-aminobenzonitrile 3a (200 mg,
1.69 mmol) in acetic acid (5 mL), in a sealed tube at room temper-
ature, were added paraformaldehyde (55.8 mg, 1.86 mmol,
1.1 equiv), potassium cyanide (121.1 mg, 1.86 mmol, 1.1 equiv), zinc
chloride (461 mg, 3.38 mmol, 2 equiv) and sulfuric acid (1 drop, ca.
16 mg). The mixture was then warmed to ca. 55 ꢀC for 3 h until no
starting material remained (TLC). The reaction mixture was allowed
to cool to rt, poured onto ice and made pH neutral (Na2CO3). Fil-
tration of the precipitate gave the title compound 4a (255 mg, 96%)
white cotton, mp 95–96 ꢀC (from cyclohexane/EtOH); (Found: C,
68.7; H, 4.4; N, 26.7. C9H7N3 requires C, 68.8; H, 4.5; N, 26.7%);
(lit.,4 172–173 ꢀC) (from cyclohexane/EtOH); vmax/cmꢁ1 3356m (NH),
3309 (NH2), 3231w, 3059 (Ar CH), 2924w, 2212s (C^N), 1628m,
1597w, 1584w, 1557m, 1493w, 1450w, 1344s, 1310s, 1292w, 1248w,
1182m, 1159s, 1105w, 1090w, 1042w, 1016w, 1009w, 932w, 891w,
814m, 746s, 739s, 727s; dH(300 MHz; DMSO-d6) 10.67 (1H, br s, NH),
7.73(1H, d,J8.1, indoleH-4), 7.24(1H, ddd,1.1, 7.5, 7.5, indoleH-5), 7.18
(1H, d, J 7.8, indole H-7), 6.94 (1H, ddd, 1.2, 7.5, 7.5, indole H-6), 5.71
(2H, br s, NH2); dC(75 MHz; DMSO-d6) 139.0 (s), 136.8 (s), 126.1 (d),
120.2 (d),118.2 (s),118.0 (d),116.2 (s),111.6 (d), 86.6 (CC^N); m/z (EI)
157 (Mþ, 100%), identical to an authentic sample.
4.2.1. 3-Amino-5,6-dimethoxyindole-2-carbonitrile 2b. Yield 25.1 mg,
89%, yellow needles, mp 194–195 ꢀC (from cyclohexane/EtOH);
(Found: C, 60.8; H, 5.0; N,19.3. C11H11N3O2 requires C, 60.8; H, 5.1; N,
lmax(DCM)/nm 228 inf (log 3
3.84), 244 (4.06), 318 (3.79); vmax/cmꢁ1
3379m (NH), 2218m (C^N), 1603s, 1582m, 1522s, 1460m, 1427w,
1317m, 1273m, 1256w, 1165m, 1134w, 1076m, 986w, 880w, 845w,
818w, 752s; dH(300 MHz; DMSO-d6) 7.55–7.51 (2H, m, Ph H-4 and
6), 6.91 (1H, d, J 8.7, Ph H-3), 6.83 (1H, dd, J 7.7, 7.7, Ph H-5), 6.78 (1H,
br m, CH2NH), 4.36 (2H, d, J 6.0, CH2NH); dC(75 MHz; DMSO-d6)
148.5 (s), 134.6 (d), 133.4 (d), 118.1 (d), 117.8 (C^N), 117.4 (C^N),
111.7 (d), 96.2 (CC^N), 31.2 (CH2); m/z (EI) 157 (Mþ, 90%), 130
(MþꢁHCN, 49), 117 (13), 103 (100), 90 (39), 76 (17), 63 (17), 51 (13).
19.3%); lmax(DCM)/nm 232 (log 3 4.24), 248 (4.24), 311 (4.33); vmax/
cmꢁ1 3426w (NH), 3347m (NH2), 3007w (Ar CH), 2949w, 2907w,
2839w, 2185s (C^N), 1636m, 1591w, 1557s, 1485s, 1462m, 1439m,
1385w, 1331s, 1319s, 1240m, 1225s, 1204s, 1190s, 1169s, 1105m,
1032w, 1001m, 910w, 853m, 822w, 806m, 754m; dH(300 MHz;
CD2Cl2) 7.46 (1H, br s, NH), 6.86 (1H, s, indole H-4 or 7), 6.73 (1H, s,
indole H-4 or 7), 3.99 (2H, br s, NH2), 3.86 (6H, s, 2ꢂCH3O);
dC(75 MHz; CD2Cl2) 151.8 (s), 146.0 (s), 138.0 (s), 132.6 (s), 115.3 (s),
111.6 (s), 99.7 (d), 94.5 (d), 89.0 (s), 56.5 (OCH3), 56.2 (OCH3), m/z (EI)
217 (Mþ,100%), 202(MþꢁCH3, 28),189(5),174 (12),159(23),147 (23),
131 (7),120 (6),117 (6),109 (6),104 (10), 90 (4), 77 (11), 63 (4), 52 (7).
4.1.2. 2-(Cyanomethylamino)-4,5-dimethoxybenzonitrile 4b. Yield
209 mg, 86%, white cotton, mp 143–144 ꢀC (from cyclohexane/
EtOH); (Found: C, 60.8; H, 5.0; N,19.25. C11H11N3O2 requires C, 60.8;
H, 5.1; N, 19.3%); lmax(DCM)/nm 232 (log
3 4.53), 260 (4.10), 324
(3.88); vmax/cmꢁ1 3370m and 3358w (NH), 2986w, 2963w, 2934w
and 2833w (CH2, CH3), 2205s (C^N), 1618s, 1587m, 1531s, 1520s,
1477m,1462w, 1450w, 1437w, 1414m, 1360w, 1341m, 1294w, 1283s,
1261m, 1250w, 1231s, 1215s, 1146m, 1078s, 1045w, 1011s, 966w,
872s, 839w, 833m, 822m; dH(300 MHz; CD2Cl2) 6.94 (1H, s, Ph H-3
or 6), 6.32 (1H, s, Ph H-6 or 3), 4.78 (1H, br t, J 6.15, CH2NH), 4.22
(2H, d, J 6.6, CH2NH), 3.92 (3H, s, CH3O), 3.78 (3H, s, CH3O);
dC(75 MHz; CD2Cl2) 155.5 (s), 144.6 (s), 143.0 (s), 117.8 (C^N), 116.6
(C^N), 115.4 (d), 96.6 (d), 88.3 (CC^N), 56.9 (CH3O), 56.4 (CH3O),
32.9 (CH2); m/z (EI) 217 (Mþ, 95%), 202 (100), 190 (5), 177 (22), 175
(16), 174 (15), 150 (12), 147 (83), 132 (15), 117 (12), 104 (18), 90 (7),
77 (20), 76 (18), 68 (15), 64 (12), 53 (13).
4.2.2. 3-Amino-5-nitroindole-2-carbonitrile 2c. Yield 56 mg, 87%,
red cotton fibres, mp 310–311 ꢀC (lit.,4 310–311 ꢀC) (from PhH); vmax
/
cmꢁ1 3463w (NH2), 3376m and 3279m (NH), 3065w, 2204s (C^N),
1635m, 1614m, 1588m, 1533m, 1521w, 1476s, 1398w, 1327s, 1244w,
1190m, 1132w, 1064m, 942w, 914w, 846w, 814m, 778w, 755m;
dH(300 MHz; DMSO-d6) 11.62 (1H, br s, NH), 8.95 (1H, d, J 2.4, indole
H-4), 8.07 (1H, dd, J 2.3, 9.2, indole H-6), 7.33 (1H, d, J 9.3, indole H-7),
6.29 (2H, br s, NH2); dC(75 MHz; DMSO-d6) 141.0 (s), 139.4 (s), 138.5
(s),120.8 (d),118.9 (d),117.2 (s),115.0 (s),112.1 (d), 87.4 (CC^N); m/z
(EI) 202 (Mþ, 100%), identical to an authentic sample.
4.3. 3-Aminoindole-2-carbonitrile 2a: (Typical conventional
heating procedure, see Table 2)
4.1.3. 2-(Cyanomethylamino)-5-nitrobenzonitrile 4c. Yield 141.6 mg,
57%, yellow cotton, mp 138–139 ꢀC (from cyclohexane/EtOH);
(Found: C, 53.45; H, 2.9; N, 27.7. C9H6N4O2 requires C, 53.5; H, 3.0;
To a stirred solution of 2-(cyanomethylamino)benzonitrile 4a
(50 mg, 0.32 mmol) in EtOH (1 mL) was added K2CO3 (22 mg,
0.16 mmol, 0.5 equiv) and the mixture was sealed in a thick glass
walled tube and heated at ca. 140 ꢀC in a preheated Wood’s metal
bath, for 90 min until no starting material remained (TLC). The
reaction mixture was then allowed to cool to ca. 20 ꢀC, added to
water (50 mL) and extracted with DCM (3ꢂ10 mL). The combined
organic extracts were dried (Na2CO3) and the volatiles removed
under reduced pressure to give the title compound 2a (28.6 mg,
57%) as light yellow cotton fibres, mp 172–173 ꢀC (lit.,4 172–173 ꢀC)
(from cyclohexane/EtOH); identical to an authentic sample.
N, 27.7%); lmax(DCM)/nm 228 (log 3 4.11), 243 inf (3.93), 327 (4.31);
vmax/cmꢁ1 3345m (NH), 3096w (Ar CH), 2978w (CH2), 2226m
(C^N), 1611m, 1587s, 1537m, 1510s, 1449w, 1339s, 1312s, 1271w,
1256w, 1179m, 1159m, 1099s, 1070w, 989w, 924w, 914m, 903w,
833m, 808m, 748s, 725w; dH(300 MHz; DMSO-d6) 8.55 (1H, d, J 2.7,
Ph H-6), 8.39 (1H, dd, J 2.7, 9.3, Ph H-4), 7.94 (1H, br s, NH), 7.11 (1H,
d, J 9.3, Ph H-3), 4.53 (2H, s, CH2); dC(75 MHz; DMSO-d6) 152.8 (s),
137.6 (s), 130.4 (d), 130.0 (d), 116.9 (C^N), 115.4 (C^N), 111.5 (d),
95.7 (CC^N), 31.3 (CH2); m/z (EI) 202 (Mþ, 100%), 185 (10), 175
(MþꢁHCN, 49), 172 (12), 158 (12), 156 (14), 148 (26), 145 (80), 129
(56), 116 (58), 102 (46), 89 (31), 75 (27), 62 (24).
4.3.1. 3-Amino-5,6-dimethoxyindole-2-carbonitrile 2b. Yield 61 mg,
88%, as yellow needles, mp 194–195 ꢀC (from cyclohexane/EtOH),
identical to that described above.
4.2. 3-Aminoindole-2-carbonitrile 2a: (Typical microwave
procedure, see Table 2)
4.3.2. 3-Amino-5-nitroindole-2-carbonitrile 2c. Yield 23.9 mg, 37%,
red cotton fibres, mp 310–311 ꢀC (lit.,4 310–311 ꢀC) (from PhH);
identical to an authentic sample.
To a stirred solution of 2-(cyanomethylamino)benzonitrile 4a
(50 mg, 0.32 mmol) in EtOH (1 mL) was added K2CO3 (22 mg,
0.16 mmol, 0.5 equiv) and the mixture was sealed and heated to ca.
120 ꢀC in a microwave reactor (250 W, 180–160 PSI), for 8 min until
no starting material remained (TLC). The reaction mixture was then
allowed to cool to rt, added to water (50 mL) and extracted with DCM
(3ꢂ10 mL). The combined organic extracts were dried (Na2CO3) and
the volatiles removed under reduced pressure to give the title com-
pound 2a (39.2 mg, 78%) as light yellow cotton fibres, mp 172–173 ꢀC
Acknowledgements
The authors wish to thank the Cyprus Research Promotion
Foundation [Grant No. TEXNOLOGIA/QEPIS/0308(BE)/08] and the
following organisations in Cyprus for generous donations of
chemicals and glassware: the State General Laboratory, the

688
S.S. Michaelidou, P.A. Koutentis / Tetrahedron 66 (2010) 685–688
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establish the NMR facility in the University of Cyprus.
15. Dotzauer, B.; Gru¨nert, R.; Bednarski, P. J.; Lanig, H.; Landwehr, J.; Troschu¨tz, R.
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