Synthesis and photochromism of 1,3-diazabicyclo[3.1.0]hex-3-ene phenol rings

Article abstract of DOI:10.1016/j.mencom.2009.07.010

The facile synthesis of mono and bis 1,3-diazabicyclo[3,1,0]hex-3-ene derivatives containing phenol ring, which behave as photochromic materials, is reported.

Full text of DOI:10.1016/j.mencom.2009.07.010

Mendeleev
Communications
Mendeleev Commun., 2009, 19, 203–205
Synthesis and photochromism of
1,3-diazabicyclo[3.1.0]hex-3-ene phenol rings
Hamzeh Kiyani, Nosrat O. Mahmoodi,* Khalil Tabatabaeian and Mohammad A. Zanjanchi
Department of Organic Chemistry, University of Guilan, P.O.Box 1914, Rasht, Iran.
Fax: +98 131 322 0066; e-mail: mahmoodi@guilan.ac.ir
DOI: 10.1016/j.mencom.2009.07.010
The facile synthesis of mono and bis 1,3-diazabicyclo[3,1,0]hex-3-ene derivatives containing phenol ring, which behave as
photochromic materials, is reported.
Photochromism is a well-known phenomenon associated with
reversible transformations of A and B, each exhibiting different
absorption characteristics upon irradiation with UV and visible
light.1–5 Photochromic compounds reversibly change not only
HN
O
R1
R2
the absorption spectra but also their geometrical and electronic
structures upon irradiation.6 Although many types of photochromic
compounds have been reported, those that exhibit photochromic
reactions in a crystal state are very rare.7,8 1,3-Diazabicyclo-
[3.1.0]hex-3-ene derivatives possess exclusive photochromic
properties. These compounds show photochromic behaviour
even in a crystalline state. Depending on the particular structure,
1,3-diazabicyclo[3.1.0]hex-3-ene derivative crystals turn yellow,
purple, blue or green upon UV irradiation.9–13 Recently, we use
novel potentiometric membrane sensors based on 6-(4-nitro-
8 R = H, R2 = NO2
9 R = NO2, R2 = H
NH4OAc, EtOH
1–7
+
OH
CHO
or
OMe
O
phenyl)-2,4-diphenyl-1,3-diazabicyclo[3.1.0]hex-2-ene
and
O
CHO
OHC
6-(4-nitrophenyl)-2-phenyl-4,4-dipropyl-3,5-diazabicyclo[3,1,0]-
hex-2-ene for the detection of tin(II)14 and strontium(II)15 at
trace levels in environmental samples, respectively. In this com-
munication, we report the synthesis of new mono-photochromic
compounds 1–5 and bis-photochromic compounds 6, 7 (Figure 1).
The general preparation of photochromic compounds 1–7 is
depicted in Scheme 1. The reaction of vanillin with 1,4-dibromo-
butane in the presence of K2CO3 in DMF leads to bis-aldehyde
10 in 80% yield.16 Reaction of either one equivalent of hydroxy
benzaldehydes or a half-equivalent of bis-aldehyde 10, and one
equivalent of ketoaziridines (8 or 9), and 10 equivalents of
ammonium acetate under anhydrous conditions afforded desired
compounds 1–7 in good yields (60–80%).†
MeO
10
Scheme 1 Synthetic route for the preparation of compounds 1–7.
The colourless solids A1–A5 after 5–25 s standing under a
fluorescence lamp or sunlight change to pale yellow and pink
solids for B1 and B5, and to blue solids for B2–B4 (Scheme 2).
Visible light did not cause photoinduced (open) form B to occur.
However, sunlight and fluorescent UV light initiated the photo-
choromism. Compounds 6 and 7, which contain two photo-
chromic centres linked by an O-alkyl spacer, upon exposure to
the above light sources undergo reversible photocyclization
R1
R2
R2
R1
OMe
N
N
N
N
N
N
O
O
R3
R4
MeO
R1
R5
R2
1 R1 = R4 = R5 = H, R2 = NO2, R3 = OH
2 R1 = R3 = R5 = H, R2 = NO2, R4 = OH
3 R1 = R3 = R4 = H, R2 = NO2, R5 = OH
4 R1 = R3 = H, R2 = NO2, R4 = OMe, R5 = OH
5 R1 = NO2, R2 = R3 = R5 = H, R4 = OH
6 R1 = H, R2 = NO2
7 R1 = NO2, R2 = H
Figure 1
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© 2009 Mendeleev Communications. All rights reserved.

Mendeleev Commun., 2009, 19, 203–205
between their closed-closed ring isomer (cc), closed-open ring
R2
R1
isomer (co) and open-open ring isomer (oo) forms (Scheme 3).
The pale orange AA6 after 15 s exposure to sunlight converted
to deep orange BB6, while colourless AA7 changes to yellow
BB7 (Scheme 3). Irradiation of the EtOH solution of 1A–5A,
6AA and 7AA at 254 nm generated the coloured open forms
1B–5B, 6BB and 7BB, which reverted to the original species
upon heating at 80–90 °C for 4–5 min.
H
N
N
H
R3
The pronounced photochromic behaviour of 2 over 5 can be
attributed to the electron-withdrawing effect of para-NO2 sub-
stitution (Scheme 2). The nitrile ylide of photoisomer 2B with
a para-NO2 group is more highly stabilized than photoisomer
5B with meta-NO2 substitution. Upon alternating irradiation
with UV and visible light, the bis- and mono-bicyclic aziridine
R5
R4
A colourless
hv1
hv2 or heat
R2
R1
R2
R1
H
H
†
Melting points were measured on a Mettler Fp5 apparatus and are
N
N
N
N
uncorrected. The IR spectra were recorded on a Shimadzu IR-470
spectrophotometer. The 1H NMR spectra were recorded on a Bruker
500 MHz instrument using solvent as an internal standard (CDCl3 at
7.26 ppm, [2H6]DMSO at 2.50 ppm). The absorption spectra in the range
200–800 nm (EtOH, c 1.0×10–4 mol dm–3), as well as the positions of
absorption band maxima for initial A (lAmax/nm) and photoinduced B
(lBmax/nm) forms were measured with a Shimadzu UV-2100 spectrophoto-
meter. The photoinduced (open) form B was formed upon UV irradiation
(Hg lamp DRSh-260+ UV-transmitting glass filters). Reversion to the
initial form A was achieved upon either storage in the dark for 1–7 days
or by heating at 80–90 °C for 4–5 min. TLC analysis was performed on
silica gel plates and column chromatography was conducted over silica
gel (mesh 200–300).
General procedure for the synthesis of mono and bis 1,3-diazabicyclo-
[3.1.0]hex-3-ene derivatives 1–7. A mixture of ketoaziridine 8 or 9 (268 mg,
1 mmol), hydroxy aldehyde (1 mmol), and ammonium acetate (750 mg,
10 mmol) in absolute ethanol (7 ml) was vigorously stirred at room tem-
perature for 2–4 days. The colour of the reaction mixture gradually
changed, and after completion of reaction solid compounds precipitated.
The reaction mixture was filtered, solids washed with EtOH (3×15 ml),
purified by column chromatography (ethyl acetate/light petroleum, 3:1)
to yield the desired compounds. Bis-1,3-diazabicyclo[3.1.0]hex-3-ene
6 and 7 were prepared analogously using bis-aldehyde 10 instead of
hydroxy aldehydes.
H
H
R3
R3
R5
R4
R5
R4
B coloured
Scheme 2 Photochromic reactions of 1,3-diazabicyclo[3,1,0]hex-3-enes
1–5.
derivatives undergo reversible cycloreversion/cyclization photo-
chromic reactions between the cc, co and oo isomers.8–11,17,18
The photochromic behaviour of 1–7 in ethanol induced by
photoirradiation at room temperature was also studied. Mono- and
bis-1,3-diazabicyclo[3.1.0]hex-3-enes showed good photochromic
properties and could be switched between their colourless closed-
ring isomers [1A–5A, 6AA (pale orange) and 7AA] and coloured
open-ring isomers (1B–5B, 6BB and 7BB) (Schemes 2 and 3).
Figure 2 shows the UV-visible spectra of 3 in EtOH (c =
= 1.0×10–4 mol dm–3). Compound 3 exhibits absorption maxima
at 205 and 262 nm at 0 s (closed form), UV irradiation causes
4-{3-Methoxy-4-[4-(2-methoxy-4-{6-(4-nitrophenyl)-4-phenyl-1,3-diaza-
bicyclo[3.1.0]hex-3-en-2-yl}phenoxy)butoxy]phenyl}-6-(4-nitrophenyl)-
2-phenyl-3,5-diazabicyclo[3.1.0]hex-2-ene 6: yield 72%, mp 195–196 °C,
pale orange solid, after irradiation with UV light converted to deep orange.
IR (KBr, n/cm–1): 3010, 2880, 1600, 1520, 1340, 1260. Closed form,
6AA: 58%, 1H NMR (500 MHz, CDCl3) d: 1.94–1.96 (q, 4H, J 2.8 and
6.0 Hz), 2.44 (s, 2H), 3.69 (s, 6H), 3.80 (s, 2H), 4.02 (t, 4H, J 6.7 Hz),
6.67 (s, 2H), 6.76 (d, 2H, J 8.5 Hz), 6.95 (d, 2H, J 7.2 Hz), 6.98–7.02
(m, 2H), 7.33 (dd, 4H, J 1.6 and 8.6 Hz), 7.41–7.44 (m, 4H), 7.48 (d,
4H, J 7.9 Hz), 7.91 (d, 4H, J 7.2 Hz), 8.09 (d, 4H, J 8.6 Hz). Open form,
6BB: 42%, 1H NMR (500 MHz, CDCl3) d: 1.94–1.96 (q, 4H, J 2.8 and
6.0 Hz), 2.70 (d, 2H, J 1.2 Hz), 3.71 (s, 6H), 3.82 (s, 6H), 4.04 (t, 4H,
J 6.8 Hz), 6.13 (d, 2H, J 2.7 Hz), 6.85 (d, 2H, J 8.5 Hz), 6.98–7.02 (m,
4H), 7.41–7.44 (m, 4H), 7.48 (d, 4H, J 7.9 Hz), 7.91 (d, 4H, J 7.2 Hz),
8.14 (d, 4H, J 8.6 Hz). UV-Vis (EtOH, lmax/nm): 206, 240 before irradia-
tion and 206, 230, 275, 315, 390 after irradiation.
2-{6-(4-Nitrophenyl)-4-phenyl-1,3-diazabicyclo[3.1.0]hex-3-en-2-yl}-
phenol 1: yield 75%, mp 167–168 °C, colourless solid, after irradiation
with UV light converted to pale pinkish. IR (KBr, n/cm–1): 3400, 3010,
1600, 1515, 1325. 1H NMR (500 MHz, CDCl3) d: 2.51 (s, 1H), 3.81 (s,
1H), 6.69 (s, 1H), 6.75 (t, 1H, J 7.5 Hz), 6.85 (d, 1H, J 8.1 Hz), 7.14
(t, 1H, J 7.7 Hz), 7.28 (d, 1H, J 7.7 Hz), 7.42–7.46 (m, 4H), 7.53 (t, 1H,
J 7.5 Hz), 7.87 (d, 2H, J 7.4 Hz), 8.16 (d, 2H, J 8.6 Hz), 9.40 (s, 1H).
UV-Vis (EtOH, lmax/nm): 205, 245, 256, 276 (sh.) before irradiation and
205, 245, 262, 405 after irradiation.
4-{6-(4-Nitrophenyl)-4-phenyl-1,3-diazabicyclo[3.1.0]hex-3-en-2-yl}-
phenol 3: yield 75%, mp 180–181 °C, colourless solid, after irradiation
with UV light converted to blue. IR (KBr, n/cm–1): 3400, 3010, 1605,
1520, 1340. Closed form, 3A: 61%, 1H NMR (500 MHz, CDCl3) d: 2.43
(s, 1H), 3.59 (s, 1H), 6.55 (s, 1H), 6.65 (d, 2H, J 8.5 Hz), 7.15 (d, 2H,
J 8.4 Hz), 7.24 (d, 2H, J 8.6 Hz), 7.33 (t, 2H, J 3.5 and 7.6 Hz), 7.37 (t,
1H, J 4.2 and 7.4 Hz), 7.80 (d, 2H, J 8.2 Hz), 7.98 (d, 2H, J 8.6 Hz),
8.50 (s, 1H). Open form, 3B: 39%, 1H NMR (500 MHz, CDCl3) d: 2.60
(d, 1H, J 1.3 Hz), 3.57 (d, 1H, J 2.1 Hz), 6.02 (d, 1H, J 2.6 Hz), 6.72 (d,
2H, J 8.4 Hz), 7.15 (d, 2H, J 8.4 Hz), 7.33 (t, 2H, J 3.5 and 7.6 Hz), 7.38
(t, 1H, J 4.2 and 7.4 Hz), 7.38 (d, 2H, J 8.7 Hz), 7.80 (d, 2H, J 8.2 Hz),
8.03 (d, 2H, J 8.6 Hz), 8.53 (s, 1H). UV-Vis (EtOH, lmax/nm): 205, 240,
262, 278 (sh.) before irradiation and 205, 240, 280, 415 after irradiation.
2-Methoxy-4-{6-(4-nitrophenyl)-4-phenyl-1,3-diazabicyclo[3.1.0]hex-
3-en-2-yl}phenol 4: yield 80%, mp 189–190 °C, colourless solid, after
irradiation with UV light converted to deep blue. IR (KBr, n/cm–1): 3400,
4-{3-Methoxy-4-[4-(2-methoxy-4-{6-(3-nitrophenyl)-4-phenyl-1,3-diaza-
bicyclo[3.1.0]hex-3-en-2-yl}phenoxy)butoxy]phenyl}-6-(3-nitrophenyl)-
2-phenyl-3,5-diazabicyclo[3.1.0]hex-2-ene 7: yield 68%, mp 175–176 °C,
colourless (almost white) solid, after irradiation with UV light converted
to yellow. IR (KBr, n/cm–1): 3010, 2900, 1600, 1515, 1340, 1260. Closed
1
form, 7AA: 52%, H NMR (500 MHz, CDCl3) d: 1.94–1.96 (m, 4H),
2.46 (s, 2H), 3.70 (s, 6H), 3.80 (s, 2H), 4.01 (t, 4H, J 6.7 Hz), 6.67 (d,
2H, J 4.2 Hz), 6.68 (s, 2H), 6.77 (d, 2H, J 8.5 Hz), 6.95 (d, 2H, J 6.7 Hz),
6.98–7.02 (m, 2H), 7.37–7.49 (m, 9H), 7.92 (d, 4H, J 7.3 Hz), 8.03–8.09
(m, 4H), 8.17 (s, 2H). Open form, 7BB: 48%, 1H NMR (500 MHz,
CDCl3) d: 1.94–1.96 (m, 4H), 2.71 (d, 2H, J 1.3 Hz), 3.73 (s, 6H), 3.82
(s, 2H), 4.04 (t, 4H, J 7.5 Hz), 6.13 (d, 2H, J 2.8 Hz), 6.85 (d, 2H, J 8.5 Hz),
6.98–7.02 (m, 4H), 7.37–7.49 (m, 9H), 7.92 (d, 4H, J 7.3 Hz), 8.03–8.09
(m, 4H). UV-Vis (EtOH, lmax/nm): 205, 242 before irradiation and 205,
280, 320, 420 after irradiation.
1
3020, 1595, 1510, 1340, 1264. H NMR (500 MHz, CDCl3) d: 2.50 (s,
1H), 3.79 (s, 1H), 3.84 (s, 3H), 6.73 (s, 1H), 6.87 (d, 1H, J 8.2 Hz), 7.00
(d, 1H, J 8.0 Hz), 7.10 (s, 1H), 7.42 (d, 2H, J 8.6 Hz), 7.51 (d, 2H,
J 7.26 Hz), 7.58 (t, 1H, J 7.5 Hz), 8.02 (d, 2H, J 7.3 Hz), 8.18 (d, 2H,
J 8.6 Hz). UV-Vis (EtOH, lmax/nm): 220, 280 before irradiation and 220,
280, 420 after irradiation.
For characteristics of compounds 2 and 5, see Online Supplementary
Materials.
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Mendeleev Commun., 2009, 19, 203–205
O2N
R2
6
R1
5
2.5
2.0
1.5
1.0
1 N
N3
H
2
25 min
20 min
15 min
10 min
5 min
N
N
N
N
3 min
1 min
HO
30 s
R1
0 s
0.5
0.0
(cc)
AA
R2
R2
190
262
334
406
478
550
hv2 or heat
hv1
l/nm
R1
Figure 2 UV-Vis absorption spectra of 3 upon irradiation under 254 nm
light in EtOH (c = 1.0×10–4) before and after successive UV irradiation
(lmax = 205, 262 nm for 3A and 205, 280, 415 nm for 3B).
N
N
N
N
absorption at 280, 415 nm for 3B due to the formation of
zwitterionic double charged imine ylide (open form).
At different irradiation times between 0–25 min, a well-defined
isosbestic point at 258 nm is observed, which indicates that clean
photochemical transformations occur (Figure 2).
R1
(co)
R2
AB
R2
3B was also converted to 3A either by stirring in the dark for
two days or after being held at 90 °C for 4–5 min. Compounds
1, 2 and 4–7 showed photochromic behaviour both in solid form
and EtOH solution comparable to 3.
hv2 or heat
hv1
R1
1
The H NMR spectrum of compound 3 in CDCl3 solution
N
N
N
N
indicates the equilibrium ratio for 3A:3B isomers at steady state
to be 61:39 upon exposure to room light. The identity of the two
isomers was easily assigned based on an analysis of the integra-
tion of four characteristic signals for each isomer: 2-H, 5-H, 6-H
and phenolic OH. Thus, the ratio of the combined integral for the
peaks at d 6.55 (s, 2-H), 3.59 (s, 5-H), 2.43 (s, 6-H) and 8.50 (s,
OH) for 3A to corresponding peaks 3B lmax = 205, 262 nm for
3A, and 205, 280, 415 nm for 3B at d 6.02 (d, 2-H), 3.57 (d, 5-H),
2.60 (d, 6-H) and 8.53 (s, OH) was ca. 1.12 to 2.86 for 3B:3A,
~39:61% at equilibrium. This ratio for bis-photochromic 6BB:6AA
or 7BB:7AA was 42:58 or 48:52, respectively (6AB and 7AB
are not distinguishable by this method). The presence of an
ortho-hydroxyphenyl group at the 2-position of the imidazoline
ring was found to induce large chemical shifts in either the
closed or open-ring forms of 1 due to hydrogen bonding with
N1 or N3 [d 9.40 (OH) instead of 8.5 for 2, 3, 5 and 7.1 for 4].
In conclusion, bicyclic aziridines represent a very interesting
class of organic compounds possessing unique photochromic
properties. These compounds form deeply coloured, fairly stable
materials under UV radiation. This property allows us to consider
them as candidates in the search for intelligent photochromic
materials.
R1
(oo)
BB
R2
OMe
=
O
O
MeO
Scheme 3 Photochromic reactions of bis 1,3-diazabicyclo[3,1,0]hex-
3-enes 6 and 7.
7
Y. Chen, M.-Li. Pang, K.-G. Cheng, Y. Wang, J. Han, Z.-J. He and
J.-B. Meng, Tetrahedron, 2007, 63, 4319 and references therein.
H. Durr, Angew. Chem., Int. Ed. Engl., 1989, 28, 413.
N. O. Mahmoodi, M. A. Zanjanchi and H. Kiyani, J. Chem. Res., 2004,
438.
8
9
10 N. O. Mahmoodi, K. Tabatabaeian, M. Arvand, H. Kiyani and
B. Sharifzadeh, Zh. Org. Khim., in press.
11 N. O. Mahmoodi and H. Kiyani, Bull. Korean Chem. Soc., 2004, 25,
1417.
12 M. R. Yazdanbakhsh, N. O. Mahmoodi and S. Dabiry, Mendeelev
Commun., 2006, 192.
This study was supported in part by the Research Committee
of University of Guilan.
13 N. O. Mahmoodi, M. R. Yazdanbakhsh, H. Kiyani and B. Sharifzadeh,
Online Supplementary Materials
J. Chin. Chem. Soc., 2007, 54, 635.
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.mencom.2009.07.010.
14 M. Arvand, M. Moghimi, A. Afshari and N. Mahmoodi, Anal. Chim.
Acta, 2006, 579, 102.
15 M. A. Zanjanchi, M. Arvand, A. Islamnezhad and N. O. Mahmoodi,
Talanta, 2007, 74, 125.
16 (a) P. K. Panda and C.-H. Lee, Org. Lett., 2004, 6, 671; (b) P. K. Panda
and C.-H. Lee, J. Org. Chem., 2005, 70, 3148.
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Received: 12th January 2009; Com. 09/3265
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