Studies on pyrimidine-annulated heterocycles: A short synthesis of novel 6,9-disubstituted cyclohepta[b]pyrimido[5,4-d]pyrrole-8(6h),10(9H)-diones

Article abstract of DOI:10.1055/s-2000-6384

A number of 6,9-disubstituted cyclohepta[b]pyrimido[5,4-d]pyrrole- 8(6H),10(9H)-dione derivatives have been synthesized in good to moderate yields by the reaction of 6-amino-3-methyluracil derivatives with 2- chlorotropone in an enamine-alkylation process

Full text of DOI:10.1055/s-2000-6384

PAPER
651
Studies on Pyrimidine-Annulated Heterocycles: A Short Synthesis of Novel
6,9-Disubstituted Cyclohepta[b]pyrimido[5,4-d]pyrrole-8(6H),10(9H)-diones
Makoto Nitta,* Yohei Tajima
Department of Chemistry, Materials Research Laboratory of Bioscience and Photonics, Waseda University, Tokyo 169-8555, Japan
Fax +81(3)32082735; E-mail: nitta@mn.waseda.ac.jp
Received 22 November 1999; revised 3 February 2000
of the products 3a-i are also summarized in Table 1. The
Abstract: A number of 6,9-disubstituted cyclohepta[b]pyrimi-
structures of the new compounds 3a-i were unequivocal-
do[5,4-d]pyrrole-8(6H),10(9H)-dione derivatives have been syn-
ly assigned on the basis of the microanalyses and the spec-
tral data (Tables 1, 2). The mass spectra showed the
thesized in good to moderate yields by the reaction of 6-amino-3-
methyluracil derivatives with 2-chlorotropone in an enamine-alk-
ylation process, subsequent condensation of the amino group with expected molecular ion peaks, and the IR spectra showed
the carbonyl function, dehydrochlorination, and dehydration.
two absorption bands in the region of n = 1685-1683 and
1637-1635 cm-1 due to the two carbonyl groups (Table
Key words: cyclohepta[b]pyrimido[5,4-d]pyrrole, 1-azaazulene, 2-
chlorotropone, 6-amino-3-methyluracil, enamine-alkylation
1
2). In the H NMR spectra, the characteristic chemical
shifts of H-1 were found at a low field of d = 9.26-9.37 as
a doublet, owing to the deshielding effect of the C-10 car-
bonyl group.16,20 Meanwhile, the 13C NMR spectra
showed two signals at d = 159.75-161.45 and 164.24-
165.15 due to the two carbonyl groups (Table 2). The
UV-VIS spectra of compounds 3a-i (Table 1) appeared
at longer wavelengths as compared to those of 7,9-di-
alkylcyclohepta[b]pyrimido[5,4-d]pyrrole-
The importance of fused pyrimidines, which are common
sources for the development of new potential therapeutic
agents,1,2 is well known. Among these, 5-deazaflavins (5-
deazaalloxazines and 5-deazaisoalloxazines) have been
studied extensively in both enzymatic3 and model
systems4,5 in the hopes of providing mechanistic insight
into flavin-catalyzed reactions. Several routes for the
preparation of 5-deaza-flavins have been previously de-
scribed.5-9 We have been interested recently in exploiting
8(7H),10(9H)diones.16
O
1
O
O
3
the
unique
reactivity
afforded
by
the
Dioxane
90°C
9
N
Me
O
Cl
vinyliminophosphoranes10,11 and related compounds12,13
in developing efficient strategies for the preparation of
fused heterocycles. In most cases, a few easy reaction
steps enable the synthesis of novel and highly interesting
types of condensed heterocycles, which are difficult to ob-
tain by other synthetic means. Since 1-azaazulene deriva-
tives have also attracted much attention in view of their
pharmacological activities,14,15 we have previously report-
ed a methodology to synthesize 7,9-dialkylcyclo-
hepta[b]pyrimido[5,4-d]pyrrole-8(7H),10(9H)-dione de-
rivatives (structural isomer of 5-deazaalloxazine).16 In
this context, as well as to pursue our interest in enzymatic
or catalytic functionalities, we now report a new facile
synthesis of novel cyclohepta[b]pyrimido[5,4-d]pyrrole-
8(6H),10(9H)-dione derivatives (structural isomer of 5-
deazaisoalloxazine), by the reaction of 6-amino-3-meth-
yluracil derivatives with 2-chlorotropone.
Me
O
N
+
Et3N
K2CO3
5
N
N
H
NHR
N
7
R
1a-i
2
3a-i
1, 3 R
Reaction
1, 3
R
Reaction
Time / h
Time / h
a
b
c
d
e
Me
Bn
25
4
f
4-ClC6H4CH2
Ph
5
20
1
g
h
i
4-MeOC6H4CH2
4-MeC6H4CH2
4-FC6H4CH2
3
4-MeOC6H4
4-ClC6H4
3
28
3
Scheme 1
Nucleophilic substitution onto a tropone carrying a mo-
bile substituent is known to take place at C-2 (usual sub-
stitution) or at C-7 (unusual substitution) to give 2-
substituted tropones.21 The present reaction of 1a-i with 2
to give 3a-i apparently does not involve a straightforward
displacement of the halide ion by the enamine-alkylation.
Thus, the reaction pathways were proven by labelling the
troponoid ring with deuterium. The reaction of 1a with 2-
chloro-3,5,7-trideuteriotropone (4) gave a mixture of 7
and 9 in a ratio of 3:1 (Scheme 2). The structural assign-
The starting 6-amino-3-methyluracil derivatives 1a, b17
and 1g-i18,19 are prepared easily as described in the liter-
ature. The new 6-amino-3-methyluracils 1c-f, also used
in this study, are prepared by a similar procedure.17-19 The
physical data of 1c-f are satisfactory and are summarized
in Tables 1 and 2. The reaction of uracils 1a-i with 2-
chlorotropone (2) in dioxane in the presence of Et3N and
K2CO3 at 90 °C leads directly to the 6,9-disubstituted
cyclohepta[b]pyrimido[5,4-d]pyrrole-8(6H),10(9H)-di-
one derivatives 3a-i, respectively (Scheme 1). The yields
1
ment of the mixture was based on HRMS and H NMR
spectral data. The HRMS of the mixture showed peaks for
Synthesis 2000, No. 5, 651–654 ISSN 0039-7881 © Thieme Stuttgart · New York

652
M. Nitta, Y. Tajima
PAPER
Table 1 6-Amino-3-methyluracils 1c-f and 6,9-Disubstituted Cyclohepta[b]pyrimido[5,4-d]pyrrole-8(6H),10(9H)-diones 3a-i
Com-
pound
Yield
(%)a
Mp (°C)
Molecular Formulab
(MW)
MS (70 eV) m/z (%)
UV (MeCN) lmax (log e) (nm)
1c
1d
1e
1f
93
94
97
93
78
85
89
86
87
74
87
93
49
273-275
277-279
288-290
288-290
298-300
269-270
238-240
232-234
285-286
293-295
>320
C13H15N3O3 (261.3)
C13H15N3O2 (245.3)
C12H12FN3O2 (249.2)
C12H12ClN3O2 (265.7)
C13H11N3O2 (241.3)
C19H15N3O2 (317.4)
C20H17N3O3 (347.4)
C20H17N3O2 (331.4)
C19H14FN3O2(335.3)
C19H14ClN3O2 (351.8)
C18H13N3O2 (303.3)
C19H15N3O3 (333.3)
C18H12ClN3O2(337.8)
261 (M+, 3), 121 (100)
245 (M+,10), 105 (100)
249 (M+, 63), 109 (100)
265 (M+, 6), 125 (100)
241 (M+, 100)
3a
3b
3c
3d
3e
3f
243 (4.19), 298 (4.74), 359 (4.01), 432 (3.46)
251 (4.28), 292 (4.44), 456 (4.33)
317 (M+, 24), 91 (100)
347 (M+, 40), 121 (100)
331 (M+, 5), 105 (100)
335 (M+, 61), 109 (100)
351 (M+, 5), 125 (100)
303 (M+, 13), 77 (100)
333 (M+, 100)
229 (4.38), 252 (4.39), 290 (4.53), 456 (4.46)
252 (4.41), 290 (4.55), 457 (4.37)
251 (4.34), 292 (4.49), 455 (4.38)
220 (4.36), 252 (4.34), 292 (4.49), 455 (4.37)
253 (4.35), 293 (4.46), 456 (4.38)
3g
3h
3i
>320
233 (4.41), 252 (4.38), 290 (4.35), 456 (4.34)
230 (4.36), 252 (4.33), 294 (4.42), 455 (4.38)
>320
339 (M+,18), 337 (100)
a Yield of isolated pure product based on 6-chloro-3-methyluracil for 1c-f and 6-amino-3-methyluracil for 3a-i.
b Satisfactory microanalysis: C 0.27, H 0.33, N 0.19.
1
Mps are uncorrected. IR and UV spectra were recorded on Horiba
FT-710 and Shimadzu UV-3101PC spectrophotometers. The H
C13H9D2N3O2 and for C13H8D3N3O2. The H NMR spec-
trum showed, besides the methyl group, three other sig-
nals at d = 9.26 (s, 1H, H-1), d = 7.87 (s, 1H, H-3), and d
= 7.74 (s, 1H, H-5) for 7 and one other signal overlapping
at d = 7.87 (s, 0.7H, H-2 and H-4) for 9. On the basis of
this assignment, the ratio of 7/9 was deduced as 3:1, and
the mechanistic pathways for the reaction of 1a with
tropone 4 were deduced as shown in Scheme 2. The initial
enamine- alkylation takes place at C-7 as well as at C-2,
and the following hydrogen migration and condensation
lead to the intermediates 6 and 8. Elimination of DCl and
HCl in addition to dehydration easily gives the final prod-
ucts 7 and 9, respectively. Compounds 1a-i are expected
to react with 2 in a similar way. In conclusion, 6-substitut-
ed-amino-3-methyluracils 1a-i are confirmed to react
with 2-chlorotropone (2) to provide a convenient route to
novel uracil-annulated 1-azaazulene derivatives, which
are the isomers of 5-deazaflavins (5-deazaisoalloxazines).
Interestingly, it was found that compounds 3a, b, g, like
the 5- deazaflavins, oxidize benzyl alcohol in the presence
of potassium carbonate and air to give benzaldehyde in
more than 100% yield based on the starting 3a, b, g. Un-
der these conditions, the 1,7-, 5,7-, or 3,7-dihydrocyclo-
hepta[b]pyrimido[5,4-d]pyrrole-8(6H),10(9H)-diones
initially formed are reoxidized to the original compounds
3a, b, g by adventitious oxygen, so that the compounds act
as turnover catalysts. The details will be reported in a sep-
arate paper in due course.
1
NMR spectra were recorded on a JEOL JNM-300 spectrometer; the
D
O
O
D
Cl
D
C-7
attack
O
Me
O
D
N
+
Me
O
Cl
D
N
O-
N
NHMe
D
H
N
H
NHMe
1a
4
5
C-2 attack
D
D
Cl
D
O
O
D
Me
Me
O
N
D
N
Cl
N
D
N
O
N
H
OH H
Me
N
OH H
Me
H
8
6
D
D
D
O
O
N
Me
O
Me
O
N
N
D
N
D/H
N
N
Me
Me
9
7
Scheme 2
Synthesis 2000, No. 5, 651–654 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Studies on Pyrimidine-Annulated Heterocycles
653
Table 2 Spectral Data of 6-Amino-3-methyluracils 1c-f and 6,9-Disubstituted Cyclohepta[b]pyrimido[5,4-d]pyrrole-8(6H),10(9H)-diones
3a-i
Com- IR n (cm-1)a 1H NMR (300 MHz) (solvent/TMS)b
13C NMR (126 MHz) (solvent/TMS) b
d
pound
d, J (Hz)
1c
1717, 1600
1718, 1604
1717, 1600
3.01 (s, 3 H, MeN), 3.73 (s, 3 H, MeO), 4.19 (d, 2 H, J = 25.74, 44.28, 54.97, 73.20, 113.83, 128.39, 129.53,
5.7, CH2), 4.55 (s, 1 H, H-5), 6.53 (br t, 1 H, NH-6), 6.91 150.78, 152.17, 158.43, 162.95
(d, 2 H, J = 8.8, H-3’, H-5’), 7.24 (d, 2 H, J = 8.8, H-2’, H-
6’)
1d
1e
1f
2.28 (s, 3 H, MePh), 3.01 (s, 3 H, MeN), 4.22 (d, 2 H, J = 20.56, 25.80, 44.51, 73.27, 126.99, 128.95, 134.77,
5.7, CH2), 4.53 (s, 1 H, H-5), 6.48 (br t, 1 H, NH-6), 7.16 136.22, 150.84, 150.22, 162.96
(d, 2 H, J = 8.0, H-3’, H-5’), 7.20 (d, 2 H, J = 8.0, H-2’, H-
6’), 10.23 (br s, 1 H, NH-1)
3.01 (s, 3 H, Me), 4.26 (d, 2 H, J = 6.0, CH2), 4.55 (s, 1 H, 5.81, 43.94, 73.33, 115.13 (d, J = 22), 129.02 (d, J = 9),
H-5), 6.55 (br t, 1 H, NH-6), 7.17 (t, 2 H, J = 8.8, H-2’,
H-6’), 7.35 (dd, 2 H, J = 5.7, 8.8, H-3’, H-5’), 10.29 (s,
1 H, H-1)
134.11 (d, J = 2), 150.86, 152.20, 161.53 (d, J = 242),
162.97
1729, 1691, 3.01 (s, 3 H, MeN), 4.28 (d, 2 H, J = 6.1, CH2), 4.52 (s,
1574
25.80, 43.94, 73.40, 128.32, 128.79, 131.57,137.07,
150.86, 152.21, 162.95
1 H, H-5), 6.58 (br t, 1 H, NH-6), 7.33 (d, 2 H, J = 8.4,
H-2’, H-6’), 7.40 (d, 2 H, J = 8.4, H-3’, H-5’), 10.33 (br s,
1 H, H-1)
3a
3b
3c
1684, 1636, 3.47 (s, 3 H, Me-9), 3.96 (s, 3 H, Me-6), 7.69-7.78 (m,
27.50, 28.42, 99.32, 121.60, 132.22, 135.52, 135.85,
1600
1 H, H-5), 7.85-7.96 (m, 3 H, H-2, H-3, H-4), 9.26 (d,1 H, 138.34, 143.14, 148.47, 159.60, 161.45, 164.23
J = 10.5, H-1)
1684, 1637, 3.52 (s, 3 H, Me-9), 5.69 (s, 2 H, CH2), 7.26-7.33 (m, 5 H, 27.58, 44.65, 99.36, 122.24, 128.67, 129.38,
1587 Ph), 7.66-7.90 (m, 4 H, H-2, H-3, H-4, H-5), 9.29 (d, 1 H, 132.49,133.10, 134.39, 135.80, 135.98, 138.68, 143.78,
J = 10.6, H-1) 148.10, 159.71, 161.57, 164.24
1684, 1636, 3.52 (s, 3 H, Me-9), 3.76 (s, 3 H, MeO), 5.62 (s, 2 H, CH2), 27.55, 44.87, 55.30, 99.26, 114.50, 122.53, 126.69,
1588 6.83 (d, 2 H, J = 8.6, H-3’, H-5’), 7.24 (d, 2 H, J = 8.6, 128.79, 132.35, 135.60, 135.96, 138.44, 143.66, 148.28,
H-2’, H-6’), 7.63-7.78 (m, 2 H, H-3, H-5), 7.82-7.93 (m, 159.56, 159.84, 161.68, 164.28
2 H, H-2, H-4), 9.28 (d, 1 H, J = 10.5, H-1)
3d
3ec
3f
1684, 1635, 2.30 (s, 3 H, MePh), 3.51 (s, 3 H, Me-9), 5.64 (s, 2 H, CH2), 21.10, 27.54, 45.15, 99.24, 122.63, 127.26, 129.78,
1598, 1588 7.11 (d, 2 H, J = 8.1, H-3’, H-5’), 7.16 (d, 2 H, J = 8.1, 131.60, 132.36, 135.63, 136.01, 138.19, 138.46, 143.65,
H-2’, H-6’), 7.63-7.93 (m, 4 H, H-2, H-3, H-4, H-5), 9.28 148.31, 159.86, 161.67, 164.28
(d, 1 H, J = 10.5, H-1)
1684, 1635, 3.51 (s, 3 H, Me-9), 5.65 (s, 2 H, CH2), 7.01 (t, 2 H, J = 8.6, 27.57, 44.62, 99.32, 116.17 (d, J = 22), 122.27, 129.15
1588
H-2’, H-6’), 7.27 (t, 2 H, J = 8.6, H-3’, H-5’), 7.68-7.80 (d, J = 8), 130.42 (d, J = 2), 132.48, 135.77, 135.97,
(m, 3 H, H-3, H-4, H-5), 7.91 (t, 1 H, J = 10.5, H-2), 9.29 138.63, 143.74, 148.15, 159.75, 162.58 (d, J = 246),
(d, 1 H, J = 10.5, H-1)
164.24
1685, 1635, 3.51 (s, 3 H, Me-9), 5.65 (s, 2 H, CH2), 7.22 (d, 2 H, J = 8.4, 27.57, 45.32, 99.31, 122.52, 127.21, 128.35, 129.15,
1597, 1588 H-2’, H-6’), 7.30 (d, 2 H, J = 8.4, H-3’, H-5’), 7.67-7.76 132.41, 134.61, 135.66, 136.01, 138.53, 143.70, 148.33,
(m, 3 H, H-2, H-3, H-5), 7.91 (t, 1 H, J = 9.5, H-4), 9.29
(d, 1 H, J = 10.6, H-1)
159.81, 161.69, 164.33
3g
3h
1685, 1635, 3.49 (s, 3 H, Me-9), 7.44 (d, 2 H, J = 7.7, H-2’, H-6’), 7.56- 27.54, 99.23, 123.27, 128.42, 130.18, 130.31, 132.63,
1602, 1583 7.75 (m, 6 H, H-2, H-4, H-5, H-3’, H-4’, H-5’), 7.90-7.98 132.81, 136.04, 136.21, 138.59, 143.32, 149.81, 159.64,
(m, 1 H, H-3), 9.37 (d, 1 H, J = 10.5, H-1) 161.75, 165.06
1684, 1635, 3.49 (s, 3 H, Me-9), 3.90 (s, 3 H, MeO), 7.11 (d, 2 H, J = 27.52, 55.75, 99.12, 115.54, 123.27, 125.12,
1595, 1584
9.2, H-3’, H-5’), 7.34 (d, 2 H, J = 9.2, H-2’, H-6’), 7.68- 129.50, 132.49, 135.88, 136.14, 138.45, 143.14, 150.13,
7.71 (m, 3 H, H-2, H-4, H-5), 7.88-7.98 (m, 1 H, H-3), 9.35 159.67, 160.75, 161.82, 165.15
(d, 1 H, J = 10.8, H-1)
3i
1683, 1635, 3.49 (s, 3 H, Me-9), 7.40 (d, 2 H, J = 8.6, H-2’, H-6’), 7.61 27.54, 99.17, 122.99, 129.74, 130.59, 131.15, 132.70,
1603, 1588
(d, 2 H, J = 8.6, H-3’, H-5’), 7.66-7.72 (m, 3 H, H-2, H-4, 136.23,136.39, 138.81, 143.44,145.90, 149.49, 159.49,
H-5), 7.73-7.98 (m, 1 H, H-3), 9.36 (d, 1 H, J = 10.8, H-1) 161.62, 164.89
a Recorded in KBr disk for 1c-f and in CHCl3 for 3a-i.
b Recorded in DMSO-d6 for 1c-f and in CDCl3 for 3a-i.
c One carbon signal was not recorded probably because of overlapping.
Synthesis 2000, No. 5, 651–654 ISSN 0039-7881 © Thieme Stuttgart · New York

654
M. Nitta, Y. Tajima
PAPER
13C NMR spectra were obtained at 126 MHz on a JNM Lambda 500
spectrometer in CDCl3; chemical shifts were related to TMS. Mass
spectra were recorded on a JMS-Automass 150 instrument.
Characterization Central Laboratory, Waseda University for techni-
cal assistance with the spectral data and elemental analyses.
6-Substituted-amino-3-methyluracils 1a, b17 and 1g-i18,19 were pre-
pared by the reaction of 6-chloro-3-methyluracil with appropriate
substituted amines according to the original procedure. All the com-
pounds gave correct spectral data.
References
(1) Brown, D. J. In Comprehensive Heterocyclic Chemistry, Vol.
3; Katritzky, A. R.; Rees, C. W., Eds.; Pergamon Press:
Oxford, 1984; pp 57-155.
(2) Wamhoff, H.; Dzenis, J.; Hirota, K. Adv. Heterocycl. Chem.
1992, 55, 129.
(3) Walsh, C. Acc. Chem. Res. 1986, 19, 216; and references cited
therein.
(4) Yoneda, F.; Tanaka, K. Med. Res. Rev. 1987, 7, 477; and
references cited therein.
(5) Yoneda, F.; Kokel, B. In Chemistry and Biochemistry of
Flavoenzymes, Vol. 1; Müller, F. Ed.; CRC Press: Boca
Raton, 1991; p 121; and references cited therein.
(6) Nishigaki, S.; Sato, J.; Shimizu, K.; Furukawa, K.; Senga, K.;
Yoneda, F. Chem. Pharm. Bull. 1980, 28, 142.
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1709.
(8) Tominaga, Y.; Okuda, H.; Tochiki, M.; Matsuda, Y.;
Kobayashi, G. Heterocycles 1981, 15, 679.
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references cited therein.
6-Amino-3-methyluracils (1c-f); General Procedure
A solution of 6-chloro-3-methyluracil (1.6 g, 10 mmol) and the ap-
propriate 4-substituted benzylamine (30 mmol) in n-BuOH (50 mL)
was heated under reflux for 3 h. The reaction mixture was cooled to
r.t., and the crystals were collected by filtration. The crystals were
washed with H2O, EtOH, and then Et2O, and were recrystallized
from n-BuOH to give 1c-f as colorless needles (Tables 1 and 2).
6,9-Disubstituted Cyclohepta[b]pyrimido[5,4-d]-pyrrole-
8(6H),10(9H)-diones (3a-i) and a mixture of 7 and 9; General
Procedure
To a solution of the appropriate 6-amino-3-methyluracil 1 (1.0
mmol) and 2-chlorotropone 2 or 4 (1.5 mmol) in dioxane (80 mL)
was added K2CO3 (414 mg, 3.0 mmol) and Et3N (20 mL). The re-
sultant mixture was stirred at 90 °C for the period recorded in
Scheme 1. The mixture was then filtered, washed with CH2Cl2, and
the filtrate concentrated under reduced pressure. The resultant resi-
due was chromatographed on Al2O3. The fractions eluted with
CH2Cl2/acetone (1:1) were concentrated and the residual solid was
recrystallized from EtOH to give 3 as light orange needles (Tables
1, 2).
(11) Nitta, M.; Iino, Y.; Mori, S.; Takayasu, T. J. Chem. Soc.,
Perkin Trans. 1 1995, 1001.
(12) Nitta, M.; Mori, S.; Iino, Y. Heterocycles 1991, 32, 23.
(13) Nitta, M.; Akie, T.; Iino, Y. J. Org. Chem. 1994, 59, 1309.
(14) Nishiwaki, T.; Fukui, T. J. Chem. Res. (S) 1986, 288.
(15) Nagahara, M.; Ieda, C.; Mimura, M.; Uchida, K.; Sato, S.;
Okamura, M. Eur. Patent. Appl. EP 376233; Chem. Abstr.
1991, 114, 23797b.
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(17) Nubel, G.; Pfleiderer, W. Chem. Ber. 1962, 95, 1605.
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1979, 16, 1365.
For a mixture of 2,4-dideuterio- and 1,3,5-trideuterio-6,9-dimethyl-
cyclohepta[b]pyrimido[5,4-d]pyrrole-8(6H),10(9H)-diones 7 and 9
in a ratio of 3:1.
Compound 7
1H NMR (300 MHz, CDCl3) d = 3.48 (s, 3H, Me-9), 3.95 (s, 3H,
Me-6), 7.74 (s, 1H, H-5), 7.87 (s, 1H, H-3), 9.26 (s, 1H, H-1).
HRMS: m/z calc for C13H9D2N3O2 (M+) 243.0978. Found:
243.0971.
(19) Yoneda, F.; Matsumoto, S.; Sakuma, Y. Chem. Pharm. Bull.
1975, 23, 2425.
(20) Abe, N.; Matsuda, H.; Sugihara, Y. J. Heterocycl. Chem.
1996, 33, 1323.
(21) Biggi, G.; Del Cima, F.; Pietra, F. J. Am. Chem. Soc. 1973, 95,
7101.
Compound 9
1H NMR (300 MHz, CDCl3) d = 3.48 (s, 3H, Me-9), 3.95 (s, 3H,
Me-6), 7.87 (s, 2H, H-2 and H-4).
HRMS: m/z calc for C13H8D3N3O2 (M+) 244.1039. Found:
244.1043.
Pietra, F. J. Chem. Soc., Chem. Commun. 1974, 544; and
references cited therein.
Acknowledgement
Article Identifier:
1437-210X,E;2000,0,05,0651,0654,ftx,en;F07299SS.pdf
Financial support from a Waseda University Grant for Special Re-
search Project is gratefully acknowledged. We thank the Materials
Synthesis 2000, No. 5, 651–654 ISSN 0039-7881 © Thieme Stuttgart · New York