Novel photo-induced coupling reaction of 9-fluorenylidenemalononitrile with 10-methyl-9,10-dihydroacridine

Article abstract of DOI:10.1039/b201239a

9-Fluorenylidenemalononitrile reacts with 10-methyl-9,10-dihydroacridine in deaerated acetonitrile under irradiation with λ > 320 nm to give a coupling product 9-dicyanomethyl-9-(10′-methyl-9′-acridinyl)fluorene, characterized by X-ray crystallographic, MS and NMR analyses.

Full text of DOI:10.1039/b201239a

Novel photo-induced coupling reaction of 9-fluorenylidenemalononitrile
with 10-methyl-9,10-dihydroacridine
Hong Jiang,a You-Cheng Liu,*a Jing Li,a Guan-Wu Wang,a Yun-Dong Wu,b Quan-Ming Wangc and
Thomas C. W. Mak*c
a Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, P. R.
China. E-mail: ycliu@ustc.edu.cn; Fax: 86 551 3631760; Tel: 86 551 3603254
b Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay,
Kowloon, Hong Kong SAR, P. R. China
c
Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
SAR, P. R. China
Received (in Cambridge, UK) 6th February 2002, Accepted 8th March 2002
First published as an Advance Article on the web 22nd March 2002
9-Fluorenylidenemalononitrile reacts with 10-methyl-
9,10-dihydroacridine in deaerated acetonitrile under irra-
diation with l > 320 nm to give a coupling product
9-dicyanomethyl-9-(10A-methyl-9A-acridinyl)fluorene, char-
acterized by X-ray crystallographic, MS and NMR analy-
ses.
was continuously irradiated with a 250 W high-pressure
mercury lamp for 24 h, a reaction took place. The reaction
mixture was worked up by a conventional procedure to give a
solid product in 70% yield. High resolution mass spectrometry
of the product gave molecular weight 423.1729, in conformity
with the molecular formula C30H21N3 (molecular weight
423.1730), which indicated that it was the coupling product 4 of
1 with AcrH2.
The mechanism of reduction reaction with 1,4-dihydropyridine
derivatives has been of continued interest because of the
important role played by the coenzyme nicotinamide adenine
dinucleotide (NADH) in biological reduction–oxidation proc-
esses.1 The two most often employed models for NADH in the
mechanistic studies are 1-benzyl-1,4-dihydronicotinamide
(BNAH) and 10-methyl-9,10-dihydroacridine (AcrH2).2,3 Pre-
viously we4 reported that the reduction of 2-bromo-1-phenyl-
ethylidenemalononitrile with BNAH produced 2-phenyl-
1,1-cyclopropanedinitrile apparently via a hydride transfer
mechanism, while the reduction of the same substrate with
AcrH2 gave the reductively debrominated dinitrile via an
electron transfer mechanism. It was also reported5,6 that the
reduction of 9-fluorenylidenemalononitrile (1) with BNAH
gave 9-dicyanomethylfluorenide carbanion 3 through the inter-
mediacy of the radical anion 2 (Scheme 1).
In order to gain further insight into the nature and reactivity
of NADH model compounds, we have investigated the reaction
of 1 with AcrH2.
Compound 1 (0.05 mmol) and AcrH2 (0.06 mmol) were
dissolved in dry, deaerated acetonitrile (10 ml) and the solution
was allowed to stand at 60 °C under argon for 24 h in the dark.
No reaction occurred. When the solution in a pyrex glass tube
The structure of 4 has been elucidated by single crystal X-ray
analysis (Fig. 1).7 The molecule is composed of a linkage of
9-dicyanomethylfluorenyl and 10A-methyl-9A-acridinyl moieties
at the C9 and C9A positions. The C9–C9A bond length is 1.582 Å,
almost 0.04 Å longer than the average length of a normal
covalent (sp3–sp3) C–C bond.8 The six-membered ring com-
posed of atoms N10A, C10A, C8AA, C9A, C9AA and C4AA is boat-
shaped with C9A and N10A as its bow and stern. The bond
configuration at the N10A atom is planar as shown by the three
bond angles C4AA–N10A–C10A, C4AA–N10A–C11A and C10A–
N10A–C11A being all very close to 120°. The structure of 4 was
1
further established by NMR spectroscopy9 including H–1H
COSY, 1H–13C COSY and 1H–13C HMBC.
Compound 4 has no sharp melting point, as it decomposes on
heating over 80 °C. It is colourless when pure but discolours
upon standing in the air.
m-Dinitrobenzene is a strong electron acceptor and an
efficient inhibitor for electron transfer reaction. When m-
dinitrobenzene (0.05 mmol) was added to the reaction mixture,
the yield of 4 was reduced to 30%.
When the reaction of 1 (0.05 mmol) with AcrH2 (0.115
mmol) was carried out in oxygen-saturated acetonitrile under
Fig. 1 Perspective view of the molecular structure of 4. The atoms are drawn
at the 30% probability level.
Scheme 1
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CHEM. COMMUN., 2002, 882–883
This journal is © The Royal Society of Chemistry 2002

irradiation for 24 h, 9H-fluoren-9-one (5) in 72.5% (on the basis
of 1) and 10-methylacridin-9(10H)-one (6) in 96.0% (on the
basis of AcrH2) were obtained (Scheme 2). In a control
experiment, when a solution of 1 in oxygen-saturated aqueous
acetonitrile was irradiated for 24 h, no 9H-fluoren-9-one was
obtained.
Scheme 4
29832040) and Special Fund for Doctoral Program from the
Ministry of Education of China (Grant No. 98035818).
Scheme 2
Notes and references
Fukuzumi et al. reported that irradiation of a solution of
AcrH2 in air-saturated acetonitrile with UV light for 25 h
produced 10-methylacridin-9(10H)-one and hydrogen perox-
ide.2a Hoz et al. reported that the superoxide radical anion
reacted with the activated olefin to give the corresponding
ketone through the intermediacy of a peroxide radical anion of
the olefin.10
We have reported that in the reaction of 1,1-diphenyl-
2,2-dinitroethylene with BNAH in oxygen-saturated acetoni-
trile, benzophenone was formed along with 1,1-diphenyl-
2,2-dinitroethane.11
In the present case, it is probable that in oxygen saturated
acetonitrile electron transfer between AcrH2 (lmax = 286 nm)
and FDCN (lmax = 347 nm) takes place under irradiation to
generate the radical cation AcrH2·+ and the radical anion 2, the
latter reacts with oxygen to produce a peroxide radical anion,
and the two radical ions then transform to the corresponding
ketones, as shown in Scheme 3.
1 (a) D. M. Strout and A. I. Meyers, Chem. Rev., 1982, 82, 223; (b) S.
Yasuo and A. Ohno, Bioorg. Chem., 1986, 14, 70; (c) F. H. Westheimer,
in Pyridine Nucleotide Coenzyme, eds. D. Dolphin, R. Poulson and O.
Avramovic, 1988, Part A, Wiley-Interscience, New York, p. 253; (d) Y.
Kim, D. G. Truhlar and M. M. Kreevoy, J. Am. Chem. Soc., 1991, 113,
7837; (e) Y. Murakami, J. Kikuchi, Y. Hisaeda and O. Hayashida,
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2 (a) S. Fukuzumi, M. Ishikawa and T. Tanaka, J. Chem. Soc., Perkin
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Am. Chem. Soc., 1983, 105, 4722; (c) L. P. Olson and T. C. Bruice,
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Chem. Soc., 1992, 114, 4694; (b) J.-M. Savéant, Acc. Chem. Res., 1993,
26, 455; (c) A. Anne, P. Hapiot, J. Moiroux, P. Neta and J.-M. Savéant,
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C. Liu, B. Li and Q. X. Guo, Tetrahedron, 1995, 9671.
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1996, 150.
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Zhu, Y. C. Liu, H. Y. Wang and W. Wang, J. Org. Chem., 1999, 64,
8982.
7 Crystal data for 4: C30H21N3, Mr = 423.50, monoclinic, P21/c, a =
9.7538(5), b = 9.4805(5), c = 24.491(1) Å, b = 95.071(1)°, V =
2255.9(2) Å3, Z = 4, m = 0.074 mm21, q-range 1.67–25.04°, 3996
independent reflections, refinement on F2 for 299 parameters, wR (F2,
all refl.) = 0.106, R1[2281 obs. refl. with I > 2s(I)] = 0.041. CCDC
175312. See http://www.rsc.org/suppdata/cc/b2/b201239a/ for elec-
tronic files in .cif or other electronic format.
8 M. J. S. Dewar and W. Thiel, J. Am. Chem. Soc., 1977, 99, 4907.
9 Selected spectral data for 4. 1H NMR (500 MHz, C6D6): d 7.23 (d, J =
7.2 Hz, 2H, H4, H5), 7.04 (d, J = 7.4 Hz, 2H, H1, H8), 6.98 (t, J = 7.2
Hz, 2H, H2, H7), 6.95 (m, 2H, H1A, H8A), 6.94 (m, 2H, H3, H6), 6.93 (m,
2H, H3A, H6A), 6.62 (t, J = 7.3 Hz, 2H, H2A, H7A), 6.27 (d, J = 8.2 Hz,
2H, H4A, H5A), 4.94 (s, 1H, H9A), 3.83 (s, 1H, H10), 2.31 (s, 1H, H11A);
13C NMR (125.8 MHz, C6D6): d 143.58 (C4AA, C10AA), 142.72 (C4A,
C4B), 142.14 (C8A, C9A), 130.22 (C1A, C8A), 129.53 (C2, C7), 128.67
(C3A, C6A), 127.22 (C3, C6), 125.12 (C4, C5), 120.87 (C2A, C7A), 120.42
(C1, C8), 119.95 (C8AA, C9AA), 112.96 (C4A, C5A, C11, C12), 59.08
(C9), 49.89 (C9A), 32.83 (C11A), 30.38 (C10). The signals of the 1H
NMR and 13C NMR spectra were assigned on the basis of 1H–1H
COSY, 1H–13C COSY and 1H–13C HMBC spectra.
Scheme 3
From the results described above it seems likely that the
coupling reaction in deaerated acetonitrile occurs via a single
electron transfer pathway. According to the quantum mechanics
calculation made on 9-fluorenylmalononitrile radical anion
(2),12 there are 0.348 units of negative charge on the Ca but little
charge on the C9, whereas the spin densities on the Ca and C9
are 0.195 and 0.246, respectively. Thus, it is conceivable that
when the radical ion pair AcrH2·+ and 2 is formed, proton
transfer from C9’ of AcrH2·+ to Ca of 2 is followed by radical
coupling between C9 and C9’ to form the product 4 (Scheme
4).
This provides a rare example of a radical coupling reaction in
the reactions of NADH models13 since, instead of the usual
electron transfer–proton transfer–electron transfer or electron
transfer–hydrogen abstraction mechanism, the reaction appears
to take place via an electron transfer–proton transfer–radical
coupling pathway.
10 S. Hoz and D. Speizman, J. Org. Chem., 1983, 48, 2904.
11 Y. C. Liu, H. Y. Wang, Q. C. Yang and T. C. W. Mak, J. Chem. Soc.,
Perkin Trans. 2, 2000, 649.
12 B. R. Li, D. P. Wang and Y. D. Wu, unpublished results.
13 (a) S. Fukuzumi, Y. Fujii and T. Suenobu, J. Am. Chem. Soc., 2001, 123,
10191; (b) M. Fujita, A. Ishida, S. Takamuku and S. Fukuzumi, J. Am.
Chem. Soc., 1996, 118, 8566.
This work was supported by National Natural Science
Foundation of China (Grant No. 20072036, Grant No.
CHEM. COMMUN., 2002, 882–883
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