Photoreaction of 2-morpholinoacrylonitrile with substituted 1-acetonaphthones. Part II

Article abstract of DOI:10.1039/b006835g

Photochemical reactions of substituted 1-acetonaphthones in the presence of 2-morpholinoacrylonitrile were investigated. The type of reaction, photocycloaddition vs. photosubstitution, is dependent on the nature of the additional substituent. The location of the additional substituent on the ring also affects the type of addition, [2 + 2] vs. [4 + 2].

Full text of DOI:10.1039/b006835g

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Photoreaction of 2-morpholinoacrylonitrile with substituted
1-acetonaphthones. Part II¤
Hamid R. Memarian,*a Masoud Nasr-Esfahania and Dietrich Doppb
a Department of Chemistry, Faculty of Sciences, University of Esfahan, 81744 Esfahan, Iran.
Fax ]98 (31) 689 732
b Institut fur Synthesechemie, Gerhard-Mercator-Universitat-GH-Duisburg, D-47048 Duisburg,
Germany. Fax ]49 (203) 379 4192
Received (in Montpellier, France) 16th August 2000, Accepted 4th December 2000
First published as an Advance Article on the web 7th February 2001
Photochemical reactions of substituted 1-acetonaphthones in the presence of 2-morpholinoacrylonitrile were
investigated. The type of reaction, photocycloaddition vs. photosubstitution, is dependent on the nature of the
additional substituent. The location of the additional substituent on the ring also a†ects the type of addition,
[2 ] 2] vs. [4 ] 2].
In the course of our studies on the photochemical behaviour
of acylnaphthalenes,1h6 especially substituted 1-aceto-
naphthones 1bÈe,7 towards captodative alkenes,8 especially 2-
morpholinoacrylonitrile, 2, we investigated the photochemical
reactions of further substituted 1-acetonaphthones. Our
earlier studies showed the occurrence of two types of reac-
tions: photosubstitution and photoaddition, which is dependent
on the nature of the additional substituent on the naphthalene
ring of 1-acetonaphthone. Our earlier results also indicated
that the type of addition, [2 ] 2] vs. [4 ] 2], is dependent on
the location of the additional substituent on the ring.7 Only in
the case of the 4-bromo derivative 1b, has photosubstitution
of bromine been observed.7 In continuation of this work,
we prepared 4-chloro-, 4-Ñuoro-, 4-methyl- and 2-
methylsubstituted 1-acetonaphthones 1fÈi, respectively, and
investigated their photochemical behaviour in the presence of
2, to ascertain the e†ect of an additional substituent on the
type of reaction.
4-chloro 1f only photosubstitution and 4-Ñuoro 1g both reac-
tions were observed, irradiation of 4-methyl 1h and 2-methyl
1i derivatives in the presence of 2 resulted in the addition of 2
to the naphthalene skeleton of 1h and 1i. IR, 1H NMR and
UV data gave useful information for the structural assignment
of the photoproducts. Characterization of the photo-
substitution product 3 in the case of 1f and 1g was achieved
by comparison of its physical and spectroscopic data with
those of 3 obtained upon irradiation of the 4-bromo derivative
1b in the presence of 2.7 Irradiation of a mixture of 1g and 1i
with 2 causes the formation of [2 ] 2]-cycloadducts 4d and
4e, respectively. 1H NMR spectra of 4d and 4e showed the
resonance of an acetyl group at 2.04 and 1.99 ppm, respec-
tively, which indicates the attachment of this group to the
cyclobutane ring.4,7 This observation is also supported by
comparison of the 1H NMR data of 4d and 4e with those of
4aÈc, which are summarized in Table 1. The UV spectra (in
chloroform solution) exhibit intense (lg e \ 3.73 and 3.52)
absorptions at 276 nm for 4d and 4e, respectively, consistent
with 1,2-adducts with styrene-type conjugation of the benzoid
ring and a residual double bond.
Results and discussion
Irradiation (j P 280 nm) of equimolar solutions of ketones
1fÈi with 2 resulted in the occurrence of one or both reactions,
depending on the type of substituent. Whereas in the cases of
The exo orientation of the morpholino group was con-
Ðrmed by exact analysis of the 500 MHz 1H NMR spectrum
of compound 4d. The 1-CH protons form an AX pattern with
2
d \ 3.28 (endo-1-H), d \ 2.67 (exo-1-H) and a geminal coup-
A
X
ling of 12.17 Hz, the high-Ðeld portion of which is additionally
split by 0.73 Hz due to a long range (W type) interaction with
2a-H (d \ 3.32). On the other side, the anisotropic e†ect of the
¤ Taken in part from the doctoral thesis work of M. Nasr-Esfahani,
University of Esfahan. For Part I, see: ref. 7.
476
New J. Chem., 2001, 25, 476È478
DOI: 10.1039/b006835g
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2001

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Table 1 Structurally relevant 1H NMR chemical shifts (d values) and
1H, 1H coupling J (Hz) of 4d and 4e in comparison with 4a, 4b and 4c
1H NMR spectrum of a crude reaction mixture after 12 h irra-
diation showed only peaks characteristic of both compounds
1e and 2.
CH CO
2a-H
3-H
4-H
J
3
2av3
4a
4b
4c
4d
4e
2.01
2.00
2.00
2.04
1.99
3.24
3.40
3.30
3.32
3.24
5.67
6.59
4.74
5.36
5.62
6.73
È
È
È
È
5.7
Experimental
6.15
6.41
6.30
5.61
All melting points were determined with a Stuart ScientiÐc
SMP2 and are uncorrected. IR spectra were obtained on a
Shimadzu IR-435 and PerkinÈElmer 983 spectrometers. UV
spectra were recorded on a Shimadzu UV-160. 1H NMR
spectra were collected on Bruker AW 80 (80 MHz), Bruker
WM 300 (300 MHz), and Bruker drx 500 (500 MHz) appar-
atus. 13C NMR spectra were recorded on a Bruker drx 500
(500 MHz) spectrometer; the DEPT technique was employed
for compound 4d. MS (EI and FD mode) spectra were
obtained on an AMD 604. Elemental analyses were run on
Heraeus CHN-O-RAPID and Carlo Erba 1106 CHN
analyzers. Preparative layer chromatography (PLC) was
carried out on 20 ] 20 cm2 plates, coated with a 1 mm layer
cyano group cis to the endo-1-H causes a deshielding e†ect on
this proton, which consequently shows this signal at a lower
Ðeld in comparison to the exo-1-H, which is cis to the morph-
olino group. A four-spin system was also observed for 2a-H,
3-H, 4-F and 1-H . The resonance for 2a-H shows a vicinal
coupling of 6.30 Hz with 3-H, coupling with 4-F (4.73 Hz) and
exo
long-range coupling with 1-H (0.73 Hz). These data indicate
that the X part of the AX system at higher Ðeld is cis to the
exo
of Merck silica gel PF , prepared by applying the silica as a
slurry and drying in air.
morpholino group, which displays an exo orientation of the
morpholino group. Such an orientation has also been
observed earlier in the case of 4c by an X-ray crystal structure
analysis as well as by an NOE signal intensity di†erence
determination for 4b.7
The formation of the [4 ] 2]-cycloadduct 5c was observed
upon irradiation of a mixture of 1i and 2. Since the structures
of 5a and 5b have been unambiguously determined an earlier
from X-ray structural analysis1 and by a NOE signal intensity
di†erence determination experiment,7 respectively, the assign-
ment for 5c was based on comparison of its 1H chemical shifts
and couplings with those obtained for 5a and 5b (Table 2) and
254
All irradiations were carried out in a pyrex cell (j [ 280
nm) using a 400 W high pressure Hg vapour lamp from
NARVA (with a 150 W high pressure mercury burner from
Philips in the case of 1g) through a water-cooled immersion
well made of Duran glass. A solution of 1 mmol of each of the
ketones 1f, h, i and 2 was irradiated in 15 mL dry benzene
(c \ 0.067 M) and in the case of 1g in 20 mL acetonitrile
(c \ 0.05 M) and continuously purged with a stream of argon
for the times given below.
on its UV spectrum. The resonance of the CH CO group at
2.53 ppm, compared with the same resonance for 5a and 5b,
Irradiation of 4-chloro-1-acetonaphthone 1f in the presence of
2-morpholinoacrylonitrile 2
3
and also the AX pattern for 3-H and 4-H with a vicinal coup-
ling of 6.32 Hz indicate 1,4-addition of 2 to 1i. The UV spec-
trum (in chloroform solution) exhibits absorption, lg e \ 2.86
and 3.27, at 273 and 242 nm, respectively, indicative of a non-
conjugated benzoid ring and residual double bond and forma-
tion of the 1,4-ethanonaphthalene skeleton. Most of the
cycloadducts are thermally unstable and undergo retro-
cleavage to the starting material on heating. Our new results
on cycloaddition support the formation of an exciplex inter-
mediate, which we proposed earlier.7
The solution was irradiated for 8 h. The solvent was evapo-
rated and PLC of the residue (tolueneÈethyl acetate, 7 : 1)
gave zone 1 (R \ 0.45, 170 mg of 1f), zone 2 (R \ 0.42, 120
f
f
mg of 2) and zone 3 (R \ 0.36, 39 mg of 3; 13% based on 1f
f
used, 74% based on 1f consumed). The latter was re-
crystallized from n-hexaneÈethyl acetate (10 : 1), m.p. 186È
187 ¡C (lit. m.p.,7 186È187 ¡C).
Irradiation of 4-Ñuoro-1-acetonaphthone 1g in the presence of 2
Product 5b was hydrolyzed to give the 1,4-diketone 6 fol-
lowing a published procedure.9 The IR spectrum of 6 showed
a broad band for both CO groups at 1714 cm~1 and the loss
of the CN group. The 1H NMR spectrum also supports the
hydrolysis of 5b and formation of 6.
The solution was irradiated for 15 h. The solvent was evapo-
rated and PLC of the residue (tolueneÈethyl acetate, 10 : 1)
gave zone 1 (R \ 0.67, 125 mg of 1g), zone 2 (R \ 0.49, 12
f
f
mg of 2) and zone 3 (R \ 0.36, 28 mg of 3), which was re-
f
crystallized from n-hexaneÈethyl acetate (10 : 1), m.p. 186È
187 ¡C (18% based on 1g used) and zone 4 (R \ 0.12, 44 mg
f
of 4d), which was recrystallized from n-hexaneÈethyl acetate
(5 : 1), m.p. 189È190 ¡C (27% based on 1g used).
rel-(2R,2aS,8bS)-8b-Acetyl-4-Ñuoro-1,2,2a,8b-tetrahydro-2-
morpholinocyclobuta[a]naphthalene-2-carbonitrile, 4d. IR
(KBr): l 2220 (CN), 1705 (CO) cm~1. 1H NMR (500 MHz,
CDCl ):d 2.04 (s, 3H, CH ), 2.38 (m , 2H, CH N), 2.50 (m ,
An interesting result was obtained upon irradiation of 5b at
253.8 nm. Whereas upon irradiation photoisomerization of 5a
into
a dihydrobenzosemibullvalene product4 by a di-p-
3
3
c
ax
c
2H, CH N), 2.67 (dd, o 2J o \ 12.17, 4J
\ 0.72, 1-exo-H),
methane rearrangement10,11 has been reported, a retro photo-
DielsÈAlder reaction was observed on irradiation of 5b. The
eq
1, 2a
3.28 (d, o 2J o \ 12.17, 1-endo-H), 3.32 (ddd, 3J
\ 6.30,
2a, 3
4J
\ 4.73, 4J
\ 0.72, 2a-H), 3.72 [m , 4H,
2a, F
2 2
2a, 1vexovH
c
(CH ) O], 5.36 (dd, 3J \ 12.81, 3J
\ 6.30 Hz, 3-H),
3, F
3, 2a
Table 2 Structurally relevant 1H NMR chemical shifts (d values)
and 1H, 1H coupling J (Hz) of 5c in comparison with 5a and 5b
6.98 (m , 1H, 8H), 7.34 (m , 2H, 6- and 7-H), 7.56 (m , 1H,
c
c
c
5-H). 13C NMR (CDCl ): d 25.13 (CH ), 42.40 (C-1), 45.51
3
3
and 45.58 ( o 3J o \ 9.47, C-2a), 47.19 [(CH ) N],48.17 (C-
CH CO
2-H
3-H
4-H
J
C, F 2 2
3
3,4
8b), 63.45 and 63.48 ( o 4J o \ 3.98, C-2), 66.57 [(CH ) O],
C, F
2 2
97.50 and 97.66 ( o 2J o \ 20.43, C-3), 116.33 (CN), 122.84
5a
5b
5c
2.53
2.53
2.53
6.93
È
È
6.77
5.32
a
4.45
4.31
4.41
7.8
7.16
6.32
C, F
and 122.90 ( o 3J o \ 6.49, C-5), 127.07 (C-8a), 127.24 and
C, F
127.28 ( o 4J o \ 4.49, C-6), 128.92 and 130.84 (C-7, C-8),
C, F
135.32 and 135.37 ( o 2J o \ 6.49, C-4a), 158.50 and 160.54
a Overlapped by aromatic hydrogen.
C, F
( o 1J o \ 257.43 Hz, C-4), 204.56 (CO). EI-MS (70 eV,
C, F
New J. Chem., 2001, 25, 476È478
477

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150 ¡C): m/z (%) 325 [M` [ 1, (0.05), 299 [M` [ HCN] (0.8),
283 [M` [ COCH ] (8), 196 [M` [ morpholine[ COCH ]
Anal. calc. for C
8.69%. Found. C, 73.77; H, 6.78; N, 8.34%.
H
N O (322.395): C, 74.51; H, 6.87; N,
20 22
2 2
3
3
(9), 188 [M` [ 2] (22), 173 [M` [ 2 [ CH ] (81), 145 [M`
3
[ 2 [ COCH ] (25), 138 [M` [ 1g] (100). UV (CHCl ): j
Irradiation of 5b
3
3
max
(lg e) 276 (3.73), 268 nm (3.74). Anal. calc. for C
(326.368): C, 69.92; H, 5.87; N, 8.58%. Found: C, 69.72; H,
5.92; N, 8.61%.
H
N O F
19 19
2 2
A solution of 50 mg (0.15 mmol) of 5b in 3 mL of acetonitrile
(c \ 0.05) contained in a quartz cell was irradiated in a
Rayonet reactor at 253.8 nm for 12 h. The reaction was fol-
lowed by TLC. TLC showed the retro-DielsÈAlder reaction of
5b and formation of 1e and 2. Solvent was evaporated. 1H
NMR of the residue showed characteristic peaks of 1e and 2.
Irradiation of 4-methyl-1-acetonaphthone 1h in the presence
of 2
The solution was irradiated for 8 h. The solvent was evapo-
rated and PLC of the residue (tolueneÈethyl acetate, 3 : 1)
gave zone 1 (R \ 0.73, 168 mg of 1h), zone 2 (R \ 0.6, 110
Hydrolysis of 5b
f
f
In adaptation of a published procedure, a suspension of 60 mg
(0.23 mmol) of CuSO É 5H O and 16 mg (0.005 mmol) of
mg of 2), and zone 3 (R \ 0.49, 35 mg of 4e; 11% based on 1h
f
used, 80% based on 1h consumed). The latter was re-
crystallized from n-hexaneÈethyl acetate (10 : 1), m.p. 138È
4
2
Na HPO É 12H O in 1 mL of water, 1.5 mL of methanol and
2
4
2
1.5 mL of acetone was stirred for 10 min, then 50 mg (0.15
mmol) of 5b was added, the mixture stirred for 6 h, and a
further 11 mg (0.003 mmol) of Na HPO É 12H O was added.
139 ¡C (decomp.).
rel-(2R,2aS,8bS)-8b-Acetyl-4-methyl-1,2,2a,8b-tetrahydro-2-
morpholinocyclobuta[a]naphthalene-2-carbonitrile, 4e. IR
(KBr): l 2220 (CN), 1710 (CO) cm~1. 1H NMR (500 MHz,
CDCl ): d 1.99 (s, 3H, COCH ); 2.22 (s, 3H, CH ); 2.41È2.54
2
4
2
After stirring for 72 h at room temperature, the organic
material was extracted with 5 mL of chloroform, the extract
was dried with MgSO and concentrated to give 40 mg of 6.
4
3
3
3
PLC, tolueneÈethyl acetate, (7 : 1), R \ 0.36, gave 32 mg
[m, 4H, (CH ) N]; AX (d \ 2.64, d \ 3.29, o 2J o \ 12.07,
2 2 AX
f
A
X
(90%) of 6 as a viscose oil.
1-CH ), 3.73È3.75 [m, 4H, (CH ) O]; AX (d \ 3.24, d \
2
2 2
A
X
5.62, 3J \ 5.61 Hz; 2a-H, 3-H); 6.95È7.41 (m, 4H,
AX
rel-(1R,4R)-1-Acetyl-1,4-dihydro-2-methoxy-1,4-ethano-
aromatics). EI-MS (70 eV, 125 ¡C): m/z (%) 295 [M` [ HCN]
naphthalene-9-one, 6. IR (Ðlm): l 1714 cm~1 (CO, br). 1H
(0.35), 279 [M` [ COCH ] (2.25), 264 [M` [ COCH
3
3
NMR (80 MHz, CDCl ):
d AB (d \ 2.15, d \ 2.60,
[ CH ] (0.45), 236 [M` [ morpholine] (0.1), 221 [M`
3
A
B
3
o 2J o \ 18, 2H, CH ); 2.51 (s, 3H, COCH ); 3.60 (s, 3H,
[ morpholine[ CH ] (0.31), 209 [M` [ morpholine
AB
2
3
3
OCH ); AX (d \ 4.21, d \ 5.32, 3J \ 6.4 Hz, 3-H, 4-H),
[ HCN] (0.71), 184 [M` [ 2] (73), 169 [1h [ CH ] or
3
A
X
AX
3
7.01È7.30 (m, 4H, aromatic H).
[M` [ 2 [ CH ] (100), 141 [1h [ COCH ] or [M` [ 2
3
3
[ COCH ] (19), 138 [M` [ 1c] (16). UV (CHCl ): j
3
3 max
H N O
(lg e) 276 (3.52), 246 nm (3.59). Anal. calc. for C
Acknowledgements
20 22
2 2
(322.395): C, 74.51; H, 6.87; N, 8.69%. Found: C, 73.97; H,
6.94; N, 8.74%.
We are thankful to the Esfahan University Research Council
for partial support of this work. H. R. M. is indebted to the
German Academic Exchange Service (DAAD) for a scholar-
ship during the period JulyÈAugust 1998.
Irradiation of 2-methyl-1-acetonaphthone 1i in the presence of 2
The solution was irradiated for 12 h. The solvent was evapo-
rated and PLC of the residue (tolueneÈethyl acetate, 3 : 1)
gave zone 1 (R \ 0.76, 165 mg of 1i), zone 2 (R \ 0.61, 120
References
f
f
mg of 2), and zone 3 (R \ 0.47, 25 mg of 5c; 8% based on 1i
1
2
3
D. Dopp, C. Kruger, H. R. Memarian and Y.-H. Tsay, Angew.
Chem., 1985, 97, 1059; D. Dopp, C. Kruger, H. R. Memarian and
Y. H. Tsay, Angew. Chem., Int. Ed. Engl., 1985, 24, 1048.
D. Dopp and H. R. Memarian, in Substituent E†ects in Radical
Chemistry, ed. H. G. Viehe, Z. Janousek and R. Merenyi, D.
Reidel Publishing Co., Dordrecht, Germany, 1986, pp. 383È385.
D. Dopp, H. R. Memarian, C. Kruger and E. Raabe, Chem. Ber.,
1989, 122, 585.
D. Dopp and H. R. Memarian, Chem. Ber., 1990, 123, 315.
D. Dopp, J. Bredehorn, A. W. Erian, A. Jung, H. Lanfermann, H.
R. Memarian, B. Muhlbacher and M. Pies, Proc. Indian Acad.
Sci., 1993, 105, 583.
f
used, 72% based on 1i consumed). The latter was re-
crystallized from n-hexaneÈethyl acetate 10 : 1), m.p. 140È
141 ¡C (decomp.).
rel-(1S,4R,9R)-1-Acetyl-1,4-dihydro-2-methyl-9-morpholino-
1,4-ethanonaphthalene-9-carbonitrile, 5c. IR (KBr): l 2210
(CN), 1705 (CO) cm~1. 1H NMR (300 MHz, CDCl ): d AB
4
5
3
(d \ 1.90, d \ 2.20, o 2J o \ 12.52, 2H, 10-CH ); 2.33 (s,
A
B
AB
2
3H, CH ); 2.53 (s, 3H, COCH ); 2.55 (m , 2H, CH N); 2.74
3
3
c
ax
(m , 2H, CH N); 3.50 (m , 2H, CH O); 3.59 (m , 2H,
eq ax
c
c
c
6
7
D. Dopp, Proc. Indian Acad. Sci., 1995, 107, 863.
H. R. Memarian, M. Nasr-Esfahani, R. Boese and D. Dopp,
L iebigs Ann./Recueil, 1997, 1023.
CH O); AX (d \ 4.41, d \ overlapped with aromatic Hs,
eq
A
X
3J \ 6.32 Hz); 6.72È7.20 (m, 5H, aromatic H and 3-H).
AX
EI-MS (70 eV, 100 ¡C); m/z (%) 322 [M`] (0.17), 307 [M`
8
9
H. G. Viehe, Z. Janousek, R. Merenyi and L. Stella, Acc. Chem.
Res., 1985, 18, 148.
G. Buchi, P. H. Liang and H. Wuest, T etrahedron L ett., 1978,
2763.
[ CH ] (0.8), 295 [M` [ HCN] (0.28), 279 [M` [ COCH ]
3
3
(0.55), 226 [M` [ COCH [ CN] (1.58), 211 [M` [ COCH
3
3
[ CN [ CH ] (0.71), 198 (1.89), 184 [M` [ 2] (55), 169 [M`
3
10 D. Dopp and H. E. Zimmerman, in Methoden der Organischen
Chemie, ed. E. Muller, Georg Thieme, Stuttgart, Germany, 1975,
vol. IV, ch. 5, pp. 413È432.
11 S. S. Hixon, P. S. Mariano and H. E. Zimmerman, Chem. Rev.,
1973, 73, 531.
[ 2 [ CH ] 100), 155 (22), 141 [M` [ 2 [ COCH ] (36),
3
3
138 [M` [ 1i] (4), 115 [M` [ 2 [ COCH [ CN] (26).
3
FD-MS (0.005 V): m/z (%) 322 [M`] (100), 226 (33), 184 (52),
138 (14). UV (CHCl ): j
(lg e) 273 (2.86), 242 nm (3.27).
3
max
478
New J. Chem., 2001, 25, 476È478