Synthesis of novel pyrano[2,3-b]quinolines from simple acetanilides via intramolecular 1,3-dipolar cycloaddition

Article abstract of DOI:10.1016/j.tetlet.2006.08.086

Some novel isoxazole and pyrazole fused pyrano[2,3-b]quinolines were synthesized from simple acetanilides via intramolecular 1,3-dipolar cycloaddition reactions involving nitrones, nitrile oxides and nitrile imines as 1,3-dipoles, in a regioselective mann

Full text of DOI:10.1016/j.tetlet.2006.08.086

Tetrahedron Letters 47 (2006) 7779–7782
Synthesis of novel pyrano[2,3-b]quinolines from simple
acetanilides via intramolecular 1,3-dipolar cycloaddition
Pabitra K. Kalita, Biswajita Baruah and Pulak J. Bhuyan*
Medicinal Chemistry Division, Regional Research Laboratory, Jorhat 785 006, Assam, India
Received 3 July 2006; revised 17 August 2006; accepted 23 August 2006
Available online 15 September 2006
Abstract—Some novel isoxazole and pyrazole fused pyrano[2,3-b]quinolines were synthesized from simple acetanilides via intra-
molecular 1,3-dipolar cycloaddition reactions involving nitrones, nitrile oxides and nitrile imines as 1,3-dipoles, in a regioselective
manner.
Ó 2006 Elsevier Ltd. All rights reserved.
The importance of quinoline and its annelated deriva-
tives is well recognized by synthetic and biological chem-
ists.1 Compounds possessing this ring system have wide
applications as drugs and pharmaceuticals.2 Pyrano-
quinolines are an important class of compounds that
constitute the basic frameworks of a number of alka-
loids of biological significance, for example, geibalasine,
ribalinine, flindersine, etc. (Fig. 1).3 Therefore, consider-
able efforts have been directed towards the preparation
and synthetic manipulation of these molecules.4 As a
result, a number of compounds have been obtained with
diverse biological activities.
found extensive use as efficient regio- and stereoselective
methods for the synthesis of a variety of natural prod-
ucts6 and other heterocyclic compounds of biological
significance.7 Cycloaddition reactions, particularly
hetero Diels–Alder reactions, are effective procedures
employed for the preparation of pyranoquinolines.8
Isoxazoles and pyrazoles are important classes of bio-
logically active compounds. They have a rich chemistry
because of their easy reductive cleavage and susceptibil-
ity to ring transformations.9
In continuation of our interest10 in the development of
highly expedient methods and syntheses of heterocyclic
compounds of biological importance, we report here
the synthesis of novel tetrahydroisoxazolo-, dihydro-
isoxazolo- and dihydropyrazolo-fused pyrano[2,3-b]-
quinolines from simple acetanilides and via intramole-
cular 1,3-dipolar cycloaddition reactions involving
nitrones, nitrile oxides and nitrile imines as 1,3-dipoles,
in a regioselective manner.
Cycloaddition reactions are among the most useful reac-
tions in synthetic and mechanistic organic chemistry.5
They allow the direct construction of a new ring with
a wide variety of substituents by simple addition of
two or more reagents. Within this class, inter- and intra-
molecular 1,3-dipolar cycloaddition reactions have
OMe
O
O
Acetanilides 1 were chosen as the parent molecules
(Scheme 1). The 2-chloro-3-formyl quinolines 2 were
prepared from 1 by modifying the existing method.11
Thus acetanilide 1a (R1 = H) on treatment with the Vils-
meier reagent (DMF + POCl3) gave 2-chloro-3-formyl
quinoline 2a in excellent yield.12 The ether derivative
3a with an isolated dipolarophile site was prepared from
2a by treatment with allyl alcohol in the presence of
sodium hydroxide (50% aqueous solution) under phase
transfer catalytic conditions.13 Allyl ether 3a, on treat-
ment with N-methylhydroxylamine hydrochloride in
OH
OH
N
O
N
O
N
H
O
Me
geibalansine
Figure 1.
ribalinine
flindersine
Keywords: Quinolines; Pyrano[2,3-b]quinolines; 1,3-Dipolar cycloaddi-
tion reaction; Nitrones; Nitrile oxides; Nitrile imines.
Corresponding author. E-mail: pulak_jyoti@yahoo.com
*
0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.08.086

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P. K. Kalita et al. / Tetrahedron Letters 47 (2006) 7779–7782
1
Table 1. Synthesis of novel pyrano[2,3-b]quinoline derivatives 5, 6, 8
and 11 via intramolecular 1,3-dipolar cycloaddition
1
R
CHO
Allyl alcohol,
R
CH3
O
DMF
POCl3
R1
R2
Mp (°C)
Yield (%)
N
H
NaOH,
TBAB
Entry
Product
N
Cl
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
5a
6a
H
H
H
H
CH3
CH3
C6H5
C6H5
CH3
CH3
C6H5
C6H5
CH3
CH3
—
153
109
167
162
142
104
139
127
149
106
203
216
224
232
214
197
75
7
67
5
73
76
75
6
78
7
87
85
78
85
83
80
2a-c
1a-c
R2
O
N
O
1
R
5b
6b
1
CHO
R
R2NHOH
5c
6c
CH3
CH3
CH3
CH3
OCH3
OCH3
H
CH3
OCH3
H
N
O
N
3a-c
4a-f
5d
6d
R2
H
R2
O
8
9
N
O
8
N7
7
5e
6e
1
H
9
R
1
6b
R
6
5
4
6b
6a
5a
1a
9a
10
5
H
6
1
4
6a
11a
5a
1a
9a
+
H
11a
2
3
1
11
8a
8b
10
3
2
11
N
O
N
O
—
—
—
—
6a-e
5a-e
8c
R2
11a
11b
11c
R2
O
N
CH3
OCH3
N
O
O
1
1
—
R
R
N
O
N
[X]
4a-f
N OH
1
1
R
CHO
R
NH2OH
Scheme 1.
N
O
N
O
3a-c
7a-c
-
the presence of triethylamine afforded the nitrone 4a as a
white solid (mp 102 °C).14 The structure of 4a was ascer-
O
N
+
O
N
1
1
R
R
NaOCl
Et3N
1
tained from the spectroscopic data. The H NMR spec-
N
8a-c
O
N
O
tra showed the presence of the N-Me protons of the
nitrone at d 3.96 as a singlet. The allylic protons
appeared at d 6.21 (m, 1H), 5.29 (dd, 2H), 5.47 (d, 2H).
On refluxing 4a in toluene at 110 °C, two isomers, 5a
(cis) and 6a (trans) of tetrahydroisoxazolo[3040:4,5]pyr-
ano[2,3-b]quinolines were obtained in 70% and 7%
yields, respectively. The structures of 5a and 6a were
determined from spectroscopic data and elemental anal-
ysis.15 The stereochemistries were determined from the
coupling constant of the H-6b and H-9a protons (for
the cis isomer J = 3.0 Hz and for the trans isomer
J = 9.0 Hz). The chemical shifts of the N-Me protons
at d 2.90 and d 2.85, respectively, as singlets further con-
firmed the involvement of the nitrone in the cycloaddi-
tion process. Both stereoisomers 5a and 6a exhibited
strong molecular ion peaks (M+H)+ at 243 (using posi-
tive ionization technique). Similarly, tetrahydroisox-
azolo[30,40:4,5]pyrano[2,3-b]quinoline derivatives 5a–e
and 6a–e were synthesized by N-methyl- and N-phenyl-
hydroxylamine with compound 4 (Table 1). It is note-
worthy that although the nitrones form easily, the
cycloaddition required forcing conditions (110 °C,
refluxing toluene). The reaction is totally regioselective
and there was no evidence of the formation of any
1,5-electrocyclized product [X].
[A]
N
N OH
O
O
1
1
R
R
NaOCl
Et3N
N
N
O
7
[Y]
Scheme 2.
data and elemental analysis (Table 1). The 1,5-electro-
cyclization product [Y] was not formed.
For the preparation of pyrazolo[30,40:4,5]pyrano[2,3-b]-
quinolines, we first synthesized hydrazone 9a via reac-
tion of aldehyde 3a with phenylhydrazine (Scheme 3).18
Chlorination of 9a with N-chlorosuccinimide in carbon
tetrachloride at 50 °C afforded chloride 10a in very good
yield.19 This intermediate could not be purified due to
decomposition. Hence, the nitrile imine was generated
in situ from the reaction of 10a with triethylamine at
80 °C which underwent intramolecular cyclization to
give exclusively, the desired dihydropyrazolo-[30,40:4,5]-
pyrano[2,3-b]quinoline 11a without the formation of
any of the 1,5-electrocyclization product [Z].20 The struc-
ture of 11a was ascertained from the spectroscopic data
and elemental analysis. Similarly, compounds 11b–c
were synthesized and characterized (Table 1). Unlike
the nitrones, the nitrile oxides and nitrile imines were
found to be highly reactive and gave the desired com-
pounds in high yields.
In order to prepare the dihydroisoxazolo[30,40:4,5]pyr-
ano[2,3-b]quinolines, we first prepared oximes 7 from 3
by treatment with hydroxylamine hydrochloride in the
presence of aqueous sodium hydroxide (Scheme 2).16
The oximes on treatment with NaOCl in the presence
of Et3N at 0–20 °C afforded the desired dihydroisox-
azolo[30,40:4,5]pyrano[2,3-b]quinolines
8 in excellent
In conclusion, we have reported the synthesis of several
novel tetrahydroisoxazolo-, dihydroisoxazolo- and
dihydropyrazolo-fused pyrano[2,3-b]quinolines from
yields via the formation of the nitrile oxides [A].17 The
structures of 8a–c were determined from spectroscopic

P. K. Kalita et al. / Tetrahedron Letters 47 (2006) 7779–7782
7781
N
NHPh
1
R
R1
CHO
O
PhNHNH2
N
N
O
Ph
3a-c
9a-c
N
N
N
O
NHPh
Cl
1
R
1
R
NCS
CCl4
Et3N
Ph
N
O
N
11a-c
10a-c
N
N
N
O
NHPh
Cl
R1
R
Et3N
N
O
N
10
[Z]
Scheme 3.
5. (a) Carruthers, W. In Cycloaddition Reactions in Organic
Synthesis. Tetrahedron Organic Chemistry Series; Perg-
amon Press: Oxford, UK, 1990; Vol. 8, (b) Oppolzer, W.
In Comprehensive Organic Synthesis; Trost, B. M., Flem-
ing, I., Paquette, L. A., Eds.; Pergamon Press: Oxford,
UK, 1991; Vol. 5, Chapter 4:1, (c) Tietze, L. F. Chem. Rev.
1996, 96, 115; (d) Broggini, G.; Chiesa, K.; Marchi, I. De.;
Martinelli, M.; Pilati, T.; Zecchi, G. Tetrahedron 2005, 61,
3525; (e) Coldham, I.; Hufton, R. Chem. Rev. 2005, 105,
2765.
6. (a) Kitahara, Y.; Kato, T.; Funanizu, M.; Otatani, N.;
Izuumi, H. Chem. Commun. 1968, 1632; (b) Crooaert, W.
N.; Clercq, E. De. Tetrahedron Lett. 1982, 23, 3291, and
references cited therein; (c) Benwell, M.; Flyan, B.;
Hockless, D. Chem. Commun. 1997, 2259.
simple acetanilides via intramolecular 1,3-dipolar cyclo-
addition reactions involving nitrones, nitrile oxides and
nitrile imines as 1,3-dipoles, in a regioselective manner.
The present intramolecular 1,3-dipolar cycloaddition
reaction strategy, which is the first example in quinoline
chemistry can be further explored for the synthesis of
various heterocycle-fused quinoline derivatives.
Acknowledgement
The authors thank the Department of Science and
Technology, India, for financial support.
7. (a) Le Bel, N. A.; Whang, J. J. J. Am. Chem. Soc. 1959, 81,
6334; (b) Jung, M. E.; Yuk-Sun, L. P.; Mansuri, M. M.;
Speltz, L. M. J. Org. Chem. 1985, 50, 1087; (c) Coldham,
L.; Hufton, R. Chem. Rev. 2005, 105, 2765.
References and notes
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J.; Breen, A. G.; Brown, J. E.; Cox, M. F.; Croft, S. L.;
Gokcek, Y.; Kendrick, H.; Phillips, R. M.; Pollet, P. L. J.
Med. Chem. 2001, 44, 3187; (c) Sahu, N. S.; Pal, C.;
Mandal, N. B.; Banerjee, S.; Raha, M.; Kundu, A. P.;
Basu, A.; Ghosh, M.; Roy, K.; Bandyopadhyay, S. Bioorg.
Med. Chem. 2002, 10, 1687; (d) Bringmann, G.; Reichert,
Y.; Kane, V. Tetrahedron 2004, 60, 3539; (e) Kournetsov,
V. V.; Mendez, L. Y. V.; Gomez, C. M. M. Curr. Org.
Chem. 2005, 9, 141.
8. (a) Magesh, C. J.; Makesh, S. V.; Perumal, P. T. Bioorg.
Med. Chem. Lett. 2004, 14, 2035; (b) Sabitha, G.; Reddy,
M. S. K.; Arundhathi, K.; Yadav, J. S. ARKIVOC 2000,
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S. K.; Kunwar, A. C. Tetrahedron 2002, 39, 7891.
9. (a) Jaeger, V.; Buss, V.; Schwab, W. Tetrahedron Lett.
1978, 3133; (b) Kotera, K.; Takano, Y.; Matsuura, A.;
Kitahonoki, K. Tetrahedron 1970, 26, 539; (c) Lang, S. A.,
Jr.; Lin, Y. I. In Comprehensive Heterocyclic Chemistry;
Katritzky, A. R., Rees, C. W., Eds.; Pergamon Press:
Oxford, 1984; Vol. 6.
2. Antimalarial Drugs II; Peters, W., Richards, W. H. G.,
Eds.; Springer Verlag: Berlin Heidelberg, New York,
Tokyo, 1984.
3. (a) Corral, R. A.; Orazi, O. O. Tetrahedron Lett. 1967, 7,
583; (b) Sekar, M.; Rajendra Prasad, K. J. J. Nat. Prod.
1998, 61, 294; (c) Puricelli, L.; Innocenti, G.; Delle
Monache, G.; Caniato, R.; Filippini, R.; Cappelletti, E.
M. Nat. Prod. Lett. 2002, 16, 95; (d) Marco, J. L.;
Carreiras, M. C. J. Med. Chem. 2003, 6, 518.
4. (a) Pozzo, J. L.; Samat, A.; Guglielmeth, R.; Dubest, R.;
Aubard, J. Helv. Chim. Acta 2004, 80, 725; (b) Ghorab, M.
M.; Abdel-Hamide, S. G.; Farrag, H. A. Acta Pol. Pharm.
2001, 58, 175; (c) Wang, Y. G.; Lin, X.-F.; Cui, S.-U.
Synlett 2004, 1175; (d) Bowman, R. M.; Grundon, M. F.;
James, K. J. J. Chem. Soc., Perkin Trans.1 1973, 10, 1055;
(e) Morel, A. F.; Larghi, E. L. Tetrahedron: Asymmetry
2004, 15, 9.
10. (a) Devi, I.; Bhuyan, P. J. Synlett 2004, 283; (b) Devi, I.;
Bhuyan, P. J. Tetrahedron Lett. 2004, 45, 8625; (c) Devi, I.;
Bhuyan, P. J. Tetrahedron Lett. 2004, 45, 7727; (d) Deb,
M. L.; Bhuyan, P. J. Tetrahedron 2005, 46, 6453.
11. Meth-Cohn, O.; Narine, B.; Tarnowski, B. Tetrahedron
Lett. 1979, 33, 3111.
12. POCl3 (9 ml, 98.28 mmol) was added dropwise to DMF
(2.7 ml, 34.65 mmol) whilst maintaining the temperature
at 0–5 °C. The mixture was allowed to stir for about
5 min. Acetanilide 1a (10.37 mmol) was then added and
the resulting solution heated for 8 h at 75–80 °C. The
reaction mixture was cooled to room temperature and
then poured into crushed ice with stirring. A pale yellow
precipitate appeared immediately and was filtered and
washed with water and then dried. The crude compound
was recrystallized from ethyl acetate. Aldehydes 2b (74%)
and 2c (67%) were prepared similarly.

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P. K. Kalita et al. / Tetrahedron Letters 47 (2006) 7779–7782
13. To a solution of 2-chloro-3-formyl quinoline 2a (8 mmol)
in dichloromethane (10 ml) were added allyl alcohol
(0.4 ml, 10 mmol) and a catalytic amount of tetrabutyl-
ammonium bromide. To this was added, 10 ml of 50%
aqueous KOH solution and the mixture was allowed to stir
for 8 h. The organic layer was separated and washed
2–3 times with water. The solvent was evaporated and the
crude product was purified by column chromatography
using 5% ethyl acetate in hexane as eluent. Compound 3a,
extraction with dichloromethane. The organic extract was
dried over anhydrous sodium sulfate and then evaporated
under reduced pressure to obtain 7a. Yield 98%, mp 156–
158 °C. H NMR (300 MHz, CDCl3): d 5.12 (dd, J = 9.6,
5.8 Hz, 2H), 5.46 (d, J = 6.4 Hz, 2H), 6.10 (m, 1H), 7.20–
7.60 (m, 4H), 8.15 (s, 1H), 8.46 (s, 1H). Compounds 7b
(94%) and 7c (88%) were prepared similarly.
1
17. To a mixture of oxime 7a (2 mmol) and Et3N (202 mg,
2 mmol) in dichloromethane (8 ml), 10% aqueous NaOCl
solution (3.5 ml) was added dropwise at ꢀ10 °C. The
reaction mixture was allowed to stir for 1 h at room
temperature. The organic phase was separated and the
solvent was removed under reduced pressure. Product 8a
was purified by preparative TLC using dichloromethane
and hexane (7:3) as eluent. Yield 87%, mp 203 °C. 1H
NMR (300 MHz, CDCl3): d 4.07 (m, 2H), 4.35 (m, 1H),
4.86 (m, 2H), 7.20–7.75 (m, 4H), 7.95 (s, 1H). 13C NMR
(75 MHz, CDCl3): d 152.2 (C-11a), 153.96 (C-1a), 147.80
(C-5a), 132.10 (C-6b), 130.55 (C-6a), 127.00 (C-6), 126.15
(C-3), 124.20 (C-2), 123.95 (C-4), 112.00 (C-5), 66.85 (C-
10), 65.50 (C-9), 30.5 (C-9a). m/z [M+H]+ 227. CHN
analysis (calcd%) C, 69.02; H, 4.43; N, 12.39; C13H10N2O2
(found%) C, 68.98; H, 4.38; N, 12.34. Compounds 8b–c
were prepared similarly.
18. Compound 3a (2 mmol) and phenylhydrazine (2.5 mmol)
in 15 ml of ethanol were reacted at room temperature for
half an hour and then warmed for 10 min. The reaction
mixture was filtered hot. The solution was evaporated and
the solid compound obtained was recrystallized from
ethanol. Compound 9a, yield 87%, mp 161–162 °C. 1H
NMR (300 MHz, CDCl3): d 5.05 (dd, J = 9.8, 6.7 Hz, 2H),
5.32 (d, J = 6.2 Hz, 2H), 5.95 (m, 1H), 6.90–7.40 (m, 9H),
8.00 (s, 1H), 8.32 (s, 1H). Compounds 9b (82%) and 9c
(77%) were prepared similarly.
1
yield 78%, mp 56 °C. H NMR (300 MHz, CDCl3) d 5.30
(dd, J = 9.7, 6.8 Hz, 2H), 5.40 (d, J = 6.00 Hz, 2H), 6.29
(m, 1H), 6.95–7.80 (m, 4H), 8.20 (s, 1H), 9.80 (s, 1H).
Compound 3b (75%) and 3c (70%) were prepared as above.
14. To a solution of 2-allyloxy 3-formylquinoline 3a (2 mmol)
in 5 ml toluene was added MeNHOHÆHCl (2 mmol), and
the reaction stirred at room temperature. NaHCO3
(168 mg, 2 mmol) was added portionwise over a period
of 5 min (NaHCO3 was not required in the case of
PhNHOH) and stirring was continued for 2 h. The solvent
was removed under reduced pressure and the product 4a
was purified by preparative TLC using CHCl3 as eluent.
Compound 4a, yield 90%, mp 102 °C. 1H NMR
(300 MHz, CDCl3) d 3.96 (s, 3H), 5.29 (dd, J = 9.8,
6.2 Hz, 2H), 5.47 (d, J = 6.0 Hz, 2H), 6.21 (m, 1H), 7.20–
7.90 (m, 4H), 8.34 (s, 1H), 8.60 (s, 1H).
15. Compound 4a (1 mmol) was refluxed in toluene (5 ml) for
10 h. The solvent was removed under reduced pressure.
The residue was purified by preparative TLC using ethyl
acetate/hexane (4:6) as eluent to give 5a and 6a. Com-
pound 5a: yield 75%, mp 153–154 °C. 1H NMR
(300 MHz, CDCl3): d 2.90 (s, 3H), 3.22 (m, 1H), 4.30
(m, 2H), 4.43 (m, 2H), 3.86 (d, J = 3.0 Hz, 1H), 7.20–7.90
(m, 4H), 8.10 (s, 1H). 13C NMR (75 MHz, CDCl3): d
152.96 (C-1a), 149.1 (C-11a), 147.89 (C-5a), 130.45 (C-6a),
127.36 (C-6), 127.22 (C-3), 123.92 (C-2), 123.84 (C-4),
112.51 (C-5), 66.8 (C-10), 65.5 (C-9), 30.5 (N-CH3), 29.5
(C-9a), 28.3 (C-6b). m/z [M+H]+ 243. CHN analysis
(calcd%) C, 69.43; H, 5.78; N, 11.57; C14H14N2O2
(found%) C, 69.40; H, 5.72; N, 11.52. Compound 6a:
yield 7%, mp 109 °C. 1H NMR (300 MHz, CDCl3): d 2.85
(s, 3H), 3.22 (m, 1H), 4.30 (m, 2H), 4.45 (m, 2H), 3.90 (d,
J = 9.0 Hz, 1H), 7.2–8.0 (m, 4H), 8.15 (s, 1H). 13C NMR
(75 MHz, CDCl3): d 152.80 (C-1a), 149.01 (C-11a), 147.00
(C-5a), 131.15 (C-6a), 126.86 (C-6), 126.20 (C-3), 124.00
(C-2), 123.70 (C-4), 113.00 (C-5), 67.5 (C-10), 65.5 (C-9),
31.0 (N-CH3), 29.5 (C-9a), 28.3 (C-6b). m/z [M+H]+ 243.
CHN analysis (calcd%) C, 69.43; H, 5.78; N, 11.57;
C14H14N2O2 (found%) C, 69.50; H, 5.91; N, 11.48.
19. To a suspension of phenylhydrazone 9a (2 mmol) in
carbon tetrachloride (10 ml) was added a solution of N-
chlorosuccinimide (2.5 mmol) in 10 ml of carbon tetra-
chloride. The reaction mixture was heated at 50 °C for 1 h,
then cooled and filtered. The filtrate was concentrated in
vacuo to afford the hydrazonyl chloride 10a. Chlorides
10b–c were prepared in a similar way and used in the next
step without further purification.
20. A mixture of compound 10a (2 mmol) and triethylamine
(2 mmol) was refluxed in toluene (15 ml) for 2 h. The
solvent was removed under reduced pressure and the
residue was purified by preparative TLC using chloroform
and hexane (1:2) as eluent to give 11a, yield 85%, mp
189 °C. 1H NMR (300 MHz, CDCl3): d 4.12 (m, 1H), 4.21
16. Compound 3a (2 mmol) in 6 ml of EtOH/H2O mixture
(1:1) was reacted with an aqueous solution of hydroxyl-
amine prepared by adding NaOH (175 mg in 4 ml H2O) to
a solution of NH2OHÆHCl (166.7 mg, 2 mmol in 3 ml
water), with stirring at room temperature. After 10 min,
the solution was clear. The reaction mixture was allowed
to stir at room temperature for 1 h after which the EtOH
was evaporated and the compound was separated by
(m, 2H), 4.69 (m, 2H), 6.95–7.72 (m, 9H), 7.82 (s, 1H). 13
C
NMR (75 MHz, CDCl3): d 154.05 (C-1a), 151.25 (C-11a),
148.00 (C-5a), 128.20 (C-6b), 129.55 (C-6a), 127.00 (C-6),
126.85, 126.20, 125.10, 124.30, 123.53 (two C), 122.19 (two
C), 121.00 [all Ar], 67.25 (C-10), 65.00 (C-9), 31.15 (C-9a).
m/z [M+H]+ 302. CHN analysis (calcd%) C, 75.75; H,
4.98; N, 13.95; C19H15N3O (found%) C, 75.65; H, 4.94; N,
13.90. Compounds 11b–c were synthesized similarly.