Photochromic spirotetrahydroazafluorenes: Part IV. First trapping of novel type of c/s-fixed photochromes based on pyridazinopyrrolo[1,2-b]isoquinoline

Article abstract of DOI:10.1080/15421400590946532

Seven novel 2′,3′-diacetyl spirotertrahydroindolizines (THIs) 3a-g were synthesized in low yield via the nucleophilic addition of the substituted isoquinoline derivatives 2a-g to diacetyl spirocyclopropene 1 in dry ether at -20°C under nitrogen atmosphere

Full text of DOI:10.1080/15421400590946532

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Photochromic
Spirotetrahydroazafluorenes:
Part IV. First Trapping of
Novel Type of cis-Fixed
Photochromes Based on
Pyridazinopyrrolo[1,2-
b]isoquinoline
Saleh Abdel-Mgeed Ahmed a
a Chemistry Department , Faculty of Science, Assiut
University , Assiut, Egypt
Published online: 31 Aug 2006.
To cite this article: Saleh Abdel-Mgeed Ahmed (2005) Photochromic
Spirotetrahydroazafluorenes: Part IV. First Trapping of Novel Type of cis-Fixed
Photochromes Based on Pyridazinopyrrolo[1,2-b]isoquinoline, Molecular Crystals and
Liquid Crystals, 430:1, 295-300, DOI: 10.1080/15421400590946532
To link to this article: http://dx.doi.org/10.1080/15421400590946532
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Mol. Cryst. Liq. Cryst., Vol. 430, pp. 295–300, 2005
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400590946532
Photochromic Spirotetrahydroazafluorenes: Part IV.
First Trapping of Novel Type of cis-Fixed Photochromes
Based on Pyridazinopyrrolo[1,2-b]isoquinoline
Saleh Abdel-Mgeed Ahmed
Chemistry Department, Faculty of Science, Assiut University,
Assiut, Egypt
Seven novel 20,30-diacetyl spirotertrahydroindolizines (THIs) 3a–g were synthe-
sized in low yield via the nucleophilic addition of the substituted isoquinoline deri-
vatives 2a–g to diacetyl spirocyclopropene 1 in dry ether at ꢀ20ꢁC under nitrogen
atmosphere for 3 h, which undergo ring opening the corresponding betaines 3000a–g
through betaine 30a–g and 300a–g as intermediates after irradiation with UV-light.
The serious decomposition of these products during purification process was mod-
erately prevented by using flash chromatography after many trials. In situ hydra-
zinolysis of THIs 3a–g with hydrazine in ethanol at ꢀ40ꢁC afforded a novel type of
cis-fixed pyridazinopyrrolo[1,2-b]isoquinolines 4a–g in moderate yield.
Keywords: cis-fixed photochromes; flash photolysis; photochromism; spirotetrahydro-
azafluorenes
INTRODUCTION
Photochromic dihydroindolizines (DHIs) and tetrahydroindolizines
(THI), which discovered and developed by Du¨rr in 1979 [1–3], they
became a very interesting class of photochromic molecules and have
been extensively studied and received particular attention owing to
their remarkable photofatigue-resistance and wide broad photochro-
mic properties [4–10].
The author is very indebted to Prof. Dr. Heinz Du¨rr at the University of Saarland
and Prof. Dr. Aboel-Magd A. Abdel-Wahab at Assiut University for their continuous
engorgement and helpful discussions.
Address correspondence to Saleh Abdel-Mgeed Ahmed, Chemistry Department,
Faculty of Science, Assiut University, 71516 Assiut, Egypt. E-mail: saleh_63
@hotmail.com
295

296
S. A. Ahmed
In continuation of our pervious work dealing with the synthesis and
photochromic properties of dihydroindolizines (DHIs) and tetrahy-
droindloizines THIs [4,10–13], this manuscript will describe: (1) differ-
ent attempts for the trapping of diacetylspirodihydroindolizines 3,
(2) their conversion into a novel type of cis-fixed pyridazinopyrrolo
[1,2-b]isoquinolines 4, and (3) photochromic behavior of the colored
betaines.
RESULT AND DISCUSSIONS
When diacetylspirocyclopropene 1 [14] was allowed to react with
p-substituted 1-phenyl-3,4-dihydroisoquinolines 2a–g which, were
prepared by modification of the Bischler-Napieraski reaction [15] in
dry ether solution at room temperature for 24 h, the desired products
SCHEME 1

Photochromic Spirotetrahydroazafluorenes: Part IV.
297
were not isolated and a black decomposed product was detected. The
photochromic THIs 3a–g were successfully isolated when the reaction
temperature was cooled down to ꢀ20ꢁC and the reaction time
decreased to only three hours (TLC Controlled). A serious decompo-
sition of these products was observed during the purification process
by SiO2 column chromatography. A very poor yield (8–22%) of diacetyl
THIs 3a–g was obtained when the flash chromatography was applied
for purification of these products (Scheme 1).
Due to the low yield of photochromic THIs 3a–g, we decided to syn-
thesize the new photochromic spirotetrahydroazafluorenes 4a–g via
treatment of the in situ prepared THIs 3a–g with hydrazine hydrate
in ethanol under cold condition (ꢀ40ꢁC) for 20 h. The pure products
were obtained after twice column chromatography using CH2Cl2 as
eluent in 27–46% yield based on the starting diacetylspirocyclopro-
pene 1. The chemical structures of the new pyridazinopyrrolo
[1,2-b]pyradazines 4a–g were clearly assigned by both analytical and
spectroscopic tools. The pyradazine ring only slightly modifies the
NMR spectra of its precursor 3a–g show the acetyl signals at
d ¼ 1.08 and 2.69 ppm, whereas in 4 these signals occur at d ¼ 1.42
and 2.83 ppm. Both prodcuts 3a–g and 4a–g are formed regioselecti-
vity [1]. Details will be published elsewhere.
Photophysical Properties
The UV-spectra of the pale yellow THI 3a–g show a maximum between
363 and 401 nm, whereas the structurally related THF 4a–g
show a hypsochromic shift up to 62 nm (Table 1). As established
previously, these absorption bands can be assigned to the locally
excited pꢀpꢂ-transition (LE) located in the butadienyl-vinyl-amine
TABLE 1 Yield [%] and m.p [ꢁC] of the New THIs 3a–g and
Pyridazinopyrrolo[1,2-b]isoquinolines 4a–g
3
4
Compound
R1
phenyl
p-CH3-phenyl
p-OCH3-phenyl
p-Cl-phenyl
p-Br-phenyl
p-I-phenyl
Yield [%]
m.p [ꢁC]
Yield [%]
m.p [ꢁC]
a
b
c
d
e
f
18
22
13
10
13
15
8
189
146
132
166
172
174
202
46
32
40
36
34
42
27
232
215
207
241
243
246
276
g
p-NO2-phenyl

298
S. A. Ahmed
FIGURE 1 Kinetic UV-Vis spectrum of the thermal fading of betaine forms of
THI 3f (cycle time¼2 s, run time ¼ 40 s) in CH2Cl2 (c¼1 ꢃ 10ꢀ4 mol lꢀ1) at
296 K.
chromophore [1,18–20] of the THIs system. Irradiation of THI
3a–g with polychromatic light in dichloromethane solution (c ¼
1ꢃ 10 ꢀ 4 M=l), afforded the colored betaines 3000a–g through the inter-
mediate 30a–g and 300a–g with absorption maximum ranged between
462, 477 and 680, 700 nm depending on the substituents in the 100
b-phenyl ring of the THI skeleton (Figs. 1, 2). The betaine forms of
THIs 3a–g loss their photochromic properties under continuous
irradiation for several cycles and drastic decomposition of both THI
3a–g and their corresponding betaines was recorded through their
absorption spectra.
Due to the chemical unstability of these THIs and their correspond-
ing betaines, the low yield formation and hard purification of these
kind of photochromic materials can be proofed. The pyridazino-
pyrrolo[1,2-b]pyradazines 4a–g showed no visible change of color on
irradiation of 4a–g in solution neither at room temperature nor at
183 K (dry ice=methanol). Only in a glass matrix at 77 K on irradiation
of 4a–g, the color of 40a–g persisting some seconds up to a few minutes
was observed.
In conclusion, novel type of photochromic THIs 3a–g and THF 4a–g
was successfully prepared after many trails by changing the reaction
condition. UV=VIS and millisecond flash photolysis were used for
determination of both absorption maxima and half-lives of the

Photochromic Spirotetrahydroazafluorenes: Part IV.
299
FIGURE 2 Millisecond flash photolysis spectrum of the betaine form of THI
3g for determination of the absorption maxium of the betaine form at different
wavelengths (325–800 nm every 25 nm) in CH2Cl2 at 296 K.
corresponding colored betaines. The new system is an interesting can-
didate for pattern recognition system and it will find its application.
REFERENCES
[1] Du¨rr, H. & Bouas-Laurent, H. (1999, 2003). Photochromism: Molecules and
Systems, Elsevier: Amsterdam, Vol. 1 and 2.
[2] Hauck, G. & Du¨rr, H. (1979). Angew. Chem., 91, 1010; Angew. Chem. Int. Ed., 18,
945.
[3] Du¨rr, H. & Hauck, G. (1979). D Offenl., 29(6), 193.
[4] Ahmed, S. A., Hartmann, T., Huch, V., Du¨rr, H., & Abdel-Wahab, A. A. (2000).
J. Phys. Org. Chem., 13, 539.
[5] Tan, Y. S., Ahmed, S. A., Du¨rr, H., Huch, V., & Abdel-Wahab, A. A. (2001). Chem.
Commun., 14, 1246.
[6] Fromm, R., Ahmed, S. A., Hartmann, T., Huch, V., Abdel-Wahab, A. A., & Du¨rr, H.
(2001). Eur. J. Org. Chem., 21, 4077.

300
S. A. Ahmed
[7] Ahmed, S. A., Abdel-Wahab, A. A., & Du¨rr, H. (2003). J. Photochem. Photobiol. A.,
154, 131.
[8] Ahmed, S. A., Weber, C., Hozien, Z. A., Hassan, Kh. M., Abdel-Wahab, A. A., &
Du¨rr, H. Unpublished results.
[9] Ahmed, S. A. (2002). J. Phys. Org. Chem., 15, 392.
[10] Ahmed, S. A. (2000). PhD Thesis, Saarland-Assiut Universities.
[11] Hartmann, H., Ahmed, S. A., Tan, Y. S., Du¨rr, H., Renn, A., & Wild, U. (2004).
Under publication.
[12] Ahmed, S. A., Abdel-Wahab, A. A., & Du¨rr, H. (2003). In: CRC Handbook of Org Photo-
chem Photobiol., Horspool, W. M. & Lenci, F. (Eds.), CRC Press: New York, Chapter 93.
[13] Ahmed, S. A. (2004). Montashefte fu¨r Chemie., 135, 1173.
[14] Du¨rr, H. (1989). Angew. Chem., 101, 427; Angew. Chem. Int. Ed. Engl., 28, 413.
[15] (a) Bischler, A. & Napieralski, B. (1893). Ber., 26, 1903.
(b) Tietze, L. F. & Eicher, T. (1981). Reaktion und Synthesen., Thieme Verlag:
Stuttgart.