Unprecedented photoinduced insertion reactions of N-methyl-1,2- naphthalenedicarboximide with phenylacetylene

Article abstract of DOI:10.3184/030823407X228795

Irradiation of N-methyl-1,2-naphthalendicarboximide 1 together with phenylacetylene in benzene afforded unprecedented reductive insertion products dihydronaphthazepinediones 2a and 2b, which were characterised by NMR spectroscopy (¹H, ¹³

Full text of DOI:10.3184/030823407X228795

JOURNAL OF CHEMICAL RESEARCH 2007
AUGUST, 437–438
RESEARCH PAPER 437
Unprecedented photoinduced insertion reactions of
N-methyl-1,2-naphthalenedicarboximide with phenylacetylene
Qingjian Liu
Department of Chemistry, Shandong Normal University, Jinan 250014, P. R. China
Irradiation of N-methyl-1,2-naphthalendicarboximide 1 together with phenylacetylene in benzene afforded
unprecedented reductive insertion products dihydronaphthazepinediones 2a and 2b, which were characterised
by NMR spectroscopy (1H, 13C), IR spectroscopy, MS, elemental analysis and assignments confirmed by X-ray
crystallographic analysis.
Keywords: photochemical reaction, N-methyl-1,2-naphthalenedicarboximide, phenylacetylene
CH3
The photochemistry of naphthalenedicarboximides with
alkenes has been intensively investigated.1-7 The main
reaction mode in the photoinduced reactions of N-methyl-1,2-
naphthalenedicarboximide 1 with alkenes is the insertion of
the alkenes between the C(=O)–N bond of the imide moiety to
give dihydronaphthazepinedione products.1,3
In the studies of photochemistry of naphthalenedi-
carboximides with alkynes, it was found that the
photoinduced cycloadditions of N-methyl-1,8-naphthalenedi-
carboximide with alkynes followed the pathway of N-methyl-
1,8-naphthalenedicarboximide with alkenes.8 But that is
not the case for 1. Irradiation of 1 with phenylacetylene in
benzene solution afforded unprecedented novel reductive
insertion products, dihydronaphthazepinediones 2a and 2b
(Scheme 1).
O
N
PhC CH
benzene
O
hν
1
H3C
Ph
N
O
O
Ph
CH3
N
+
O
O
2a
2b (60 : 40)
Scheme 1
The structures of 2a and 2b were fully established by NMR
(1H, 13C), MS, IR spectroscopy and elemental analysis. 2-
Methyl-4-phenyl-3,4-dihydro-1H-naphth[1,2-c]azepine-
1,5(2H)-dione 2a: colourless crystals from petroleum ether-
ethyl acetate, m.p. 161–162°C; δH (300 MHz) 8.50–8.47 (1H,
d, J = 6.9 Hz), 8.02 (1H, d, J = 8.4 Hz), 7.95–7.92 (1H, dd,
J = 9.6 and 4.0 Hz), 7.68–7.63 (2H, m), 7.42 (1H, d, J = 7.2
Hz), 7.31 (3H, m, br.), 7.10 (2H, s, br.), 4.42–4.33 (2H, m),
3.49 (1H, m), 3.39 (3H, s) ppm; δC (75 MHz) 205.2, 167.4,
135.8, 133.8, 132.0, 131.9, 130.8, 129.7, 129.6, 128.7, 128.6,
128.5, 128.4, 128.3, 128.1, 123.9, 60.2, 52.8, 34.6 ppm; νmax
:
1684 (imide), 1650 (imide), 1459, 1398, 1258, 775 cm-1;
m/z 315(M+, 6), 272(24), 211(39), 167(38), 126(47), 104(100).
Found: C 80.25, H 5.3, N 4.6; Calcd. for C21H17NO2: C 79.98,
H 5.43, N 4.44.
4-Methyl-2-phenyl-3,4-dihydro-1H-naphth[2,1-c]azepine-
1,5(2H)-dione 2b: Colourless crystals from petroleum ether-
ethyl acetate, m.p. 144–146°C. δH (300 MHz) 8.08 (1H, d,
J = 8.4 Hz), 7.93 (1H, d, J = 8.6 Hz), 7.90 (1H, d, J = 8.4 Hz),
7.58–7.53 (1H, m), 7.44–7.41 (2H, m), 7.31–7.25 (3H, m),
7.15–7.12 (2H, m), 4.47 (1 H, dd, J = 11.8 and 3.9), 4.31 (1H,
dd, J = 14.6 and 11.8) and 3.60 (1 H, dd, J = 14.6 and 3.9),
3.28 (3H, s) ppm; δC (75 MHz) 203.5, 169.3, 135.3, 135.1,
134.3, 132.7, 132.1, 131.3, 130.1, 129.6, 129.2, 128.7, 128.5,
128.2, 126.6, 125.6, 63.3, 52.5, 35.6 ppm; νmax: 1694 (imide),
1645 (imide), 1482, 1397, 1253, 763 cm-1; m/z 315(M+, 23),
272(38), 211(46), 167(42), 126(43), 104(100). Found: C
80.35, H 5.5, N 4.3; Calcd. for C21H17NO2: C 79.98, H 5.43,
N 4.44.
The structure of 2a has also been determined and confirmed
by single crystal X-ray crystallographic analysis (Fig. 1),
which unambiguously differentiated the two regioisomers 2a
and 2b which were incorrectly assigned before.3 Crystal data
for 2a: C21H17NO2, M = 315.37, monoclinic, a = 37.890(8),
b = 11.820(2), c = 15.020(3) Å, V = 6592(2) Å3, T = 293(2)
K, space group C2/c, Z = 16, 5884 reflections measured, 5792
Fig. 1 The X-ray crystal structure ORTEP diagram of 2a.
unique (Rint = 0.025), which were used in all calculations.
The final wR (F2) was 0.257 (all data).
It may be rationalised that 2a and 2b resulted from reduction
of primary products 3a and 3b which were the insertion
products of phenylacetylene between the C(=O)–N bond of
the imide moiety. A similar observation has also been made for
the photoinduced reaction of 1 with t-butylacetylene.9 Alibés
et al.10 reported that the photocycloaddition of acetylene and
furanones gave rise to cyclobutanes and not the expected
cyclobutenes. The mechanisms of the C=C bond reduction in
the naphthazepinediones need to be further investigated.
H3C
Ph
N
O
O
Ph
CH3
N
O
O
* Correspondent. E-mail: liuqj@sdnu.edu.cn
3a
3b
PAPER: 07/4464

438 JOURNAL OF CHEMICAL RESEARCH 2007
the supplementary crystallographic data for this paper.
The data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request.cif.
Experimental
Melting points are uncorrected. 1H NMR spectra were measured on a
Bruker DPX 300 spectrometer at 300 MHz or 500 MHz with CDCl3
as solvent. 13C NMR spectra were measured on a Bruker Avance 300
spectrometer at 100 MHz with CDCl3 as solvent. IR spectra were
recorded with a Shimadzu IR 440 spectrometer in KBr pellets. Mass
spectra were taken on a VG ZAB-HS spectrometer in the electron
impact ionisation mode. Elemental analyses were performed with a
Perkin-Elmer 240 C analyser.
Received 7 February 2007; accepted 9 July 2007
Paper 07/4464 doi: 10.3184/030823407X228795
References
A solution of N-methyl-1, 2-naphthalenedicarboximide 1 (633 mg,
3.0 mmol) and phenylacetylene (2.04 g, 20 mmol) in benzene
(100 ml) was irradiated with UV light of λ > 330 nm using a medium-
pressure mercury lamp (500 W) for 12 h. After evaporation of the
solvents under reduced pressure, the residue was subjected to flash
chromatography on a silica gel (300–400 mesh) column to afford 2a
(458 mg, 57%) and 2b (305 mg, 38%), and recovered 1 (95 mg, 85%
conversion).
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The author gratefully acknowledges Professor Jianhua Xu of
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National Natural Science Foundation of China (NSFC) for
financial support.
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Supporting Information (SI) available
9
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1H NMR spectra of compounds 2a and 2b are available
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PAPER: 07/4464