Efficient synthesis of novel bis(dipyrromethanes) with versatile linkers via indium(III) chloride-catalyzed condensation of pyrrole and dialdehydes

Article abstract of DOI:10.1002/adsc.201000336

A new efficient and mild protocol for synthesizing a series of novel bis(dipyrromethanes) with versatile arylene linkers through an indi- um(III) chloride-catalyzed condensation reaction between various dialdehydes and pyrrole has been developed. This protocol is applicable to constructing a variety of bis(dipyrromethanes) with diverse functional linkers, which provides a powerful route to construct libraries of functionalized porphyrin dimers and even multiporphyrin arrays. Copyright

Full text of DOI:10.1002/adsc.201000336

UPDATES
DOI: 10.1002/adsc.201000336
Efficient Synthesis of Novel Bis(dipyrromethanes) with Versatile
Linkers via Indium(III) Chloride-Catalyzed Condensation of
G
Pyrrole and Dialdehydes
Hongbin Zhao,a,b,* Junxu Liao,a Jingheng Ning,a Yujia Xie,a Yingjie Cao,a
Liang Chen,a Deliang Yang,a and Bangying Wanga
a
College of Chemistry, Xiangtan University, Hunan 411105, Peopleꢀs Republic of China
Fax : (+86)-731-5829-2477; phone: (+86)-138-2722-3583; e-mail: zhaohbhanlf@163.com
College of Chemistry and Environmental Engineering, Dongguan University of Technology, Guangdong 523808, Peopleꢀs
b
Republic of China
Received: April 30, 2010; Revised: September 28, 2010; Published online: November 17, 2010
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201000336.
Abstract: A new efficient and mild protocol for
synthesizing a series of novel bis(dipyrromethanes)
with versatile arylene linkers through an indi-
pyrromethanes), especially those containing versatile
functionalized linkers.
The basic idea of making bis(dipyrromethanes)
from a diformyl compound was demonstrated first by
Chang in the 1980s and exploited by Sessler, McLen-
don, Osuka, Lindsey and others.[7] Most of the report-
ed bis(dipyrromethanes) were utilized to synthesize
diporphyrins via condensation of each bis(dipyrrome-
thane) with two dipyrromethane units. Nevertheless,
to the best of our knowledge, except these above-
mentioned diporphyrins, multiporphyrin arrays with
more porphyrin units have not yet been obtained
through condensation reactions of bis(dipyrrome-
thanes), without coupling intact porphyrin building
blocks.
umACHTUNGTRENNUNG(III) chloride-catalyzed condensation reaction
between various dialdehydes and pyrrole has been
developed. This protocol is applicable to construct-
ing a variety of bis(dipyrromethanes) with diverse
functional linkers, which provides a powerful route
to construct libraries of functionalized porphyrin
dimers and even multiporphyrin arrays.
Keywords:
bis(dipyrromethanes);
dialdehydes;
indium
roles
ACHTUNGTRENNUNG(III) chloride-catalyzed condensation; pyr-
Herein, we report a general and efficient protocol
to synthesize a series of novel bis(dipyrromethanes)
containing various arylene linkers via InCl3-catalyzed
The organization of multiple porphyrins into arrays condensation of functionalized dialdehydes and pyr-
has provided the basis for a variety of functional mo- role (Scheme 1). We also obtained new diporphyrins
lecular architectures.[1–4] The research into the design using these novel bis(dipyrromethanes) for cyclization
and synthesis of novel multiporphyrin arrays has at- with dipyrromethanes under mild conditions. This
tracted much attention. The common method for con- method could be applied to constructing novel multi-
structing multiporphyrin arrays is coupling intact por- porphyrin arrays that contain numerous porphyrin
phyrin building blocks;[5] however, this inconvenient units. These multiporphyrin arrays could be synthe-
stepwise approach only introduces fixed linkers sized through simultaneous condensation–cyclization–
among the porphyrin units, which seriously limits the polymerization of different or the same bis(dipyrro-
possible diversity and functionality of the multipor-
phyrin arrays. The condensation of bis(dipyrrome-
thanes) by the “2+2” method is a potentially impor-
tant strategy for the design and synthesis of novel
multiporphyrin arrays,[6] since the tunability of linkers
in bis(dipyrromethanes) offers more opportunities to
construct multiporphyrin arrays with targeted func-
tions. Thus, the key procedure in this strategy is how
to obtain the vital intermediate compounds – bis(di- satile linkers.
Scheme 1. Synthesis of bis(dipyrromethanes) containing ver-
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Hongbin Zhao et al.
UPDATES
methane) monomers, and the polymerization reaction modifications, e.g., compounds 2,[8] 3,[8] and 6;[9] proce-
could be terminated by dipyrromethanes. It should be dures for the synthesis of compounds 4 and 5 are
noted that by this method, multiporphyrin arrays with given in the Experimental Section and Supporting In-
more porphyrin units bearing versatile linkers could formation, respectively.
be prepared just by one step. Thus, a series of func-
Furthermore, biphenylene-linked dialdehydes were
tionalized multiporphyrin arrays could be obtained by prepared by using Suzuki–Miyaura coupling as the
this one-step method easily and this offers us a good key reaction (Scheme 2). Starting with compound
chance to further study the properties of multipor- 8,[8b] we performed a Br/Li-exchange with n-BuLi fol-
phyrin compounds. Our work will significantly extend lowed by reaction with DMF affording aldehyde 9,[10]
and enrich porphyrin chemistry.
and aldehyde 14 was gained by the same method by
With the ultimate objective of constructing a series using compound 13[11] as starting material. Subse-
of novel multiporphyrin arrays, a series of phenylene- quently, cross-coupling of 9 (or 14) and 4-formylphe-
linked, biphenylene-linked, triphenylene-linked, and nylboronic acid gave the dialdehyde 10 (or 15).[12]
triphenylenevinylene-linked dialdehydes with various Boronate 11 was prepared from 9 by modified
functional groups has been prepared. Firstly, as can Miyaura coupling with bis(pinacolato)diboron.[13] Fi-
be seen from Table 1, both electron-deficient and nally, cross-coupling of 11 and 9 gave the correspond-
electron-rich functional groups (entries 2–6) can be ing 12 (see Supporting Information).
smoothly incorporated into phenylene-linked dialde-
hydes according to literature procedures or with some sized via an analogous procedure (Table 2). Suzuki
bis-coupling of either or 1,4-dibromo-2,5-bis-
(decyloxy)benzene[14] with 4-formylphenylboronic
The terphenylene-linked dialdehydes were synthe-
8
AHCTUNGTRENNUNG
Table 1. Phenylene-linked dialdehydes.
acid afforded either the dialdehyde 16 or 18 in good
yields (75% and 67%, respectively).[12] Dialdehyde 17
was prepared by bis-coupling of 9 with 1,4-diboronate
derived from 8 via Miyaura cross-coupling reaction
(see Supporting Information).
Three triphenylenevinylene-linked dialdehydes
were also prepared during our experiments (Table 3).
Compound 21 was produced according to the pub-
lished procedure.[9] Firstly, 2,5-bis(bromomethyl)-1,4-
Entry
Dialdehyde
R1
R2
1
2
3
4
5
6
1[a]
2
3
4
5
H
Br
Br
OC4H9
OC7H15
OC10H21
H
H
Br
OC4H9
OC7H15
OC10H21
bis
nium salt, and then a double Wittig reaction with di-
aldehyde 1, 4 or 6 gave the corresponding triphenyl-
enevinylene-linked dialdehyde 19, 20 or 21 in high
yields of 87%, 82% and 84%, respectively.
ACHTUNGTREN(NUNG decyloxy)benzene was converted to a diphospho-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
6
[a]
Compound 1 was commercially available.
Scheme 2. Synthesis of biphenylene-linked dialdehydes.
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Efficient Synthesis of Novel Bis(dipyrromethanes) with Versatile Linkers
Table 2. Terphenylene-linked dialdehydes.
Table 4. Synthesis of phenylene-linked bis(dipyrrome-
thanes).
Entry
Dialdehyde
R1
R2
Dialdehyde Bis(dipyrro- R1
methanes)
R2
Time Yield
[min] [%]
1
2
3
16
17
18
CH3
CH3
OC10H21
H
CH3
H
1
2
3
4
5
6
22a
22b
22c
22d
22e
22f
H
Br
Br
H
H
Br
120
120
120
93
81
77
90
88
85
OC4H9 OC4H9 120
OC7H15 OC7H15 120
OC10H21 OC10H21 120
Table 3. Triphenylenevinylene-linked dialdehydes.
Extension of the method to terphenylene-linked
bis(dipyrromethanes) as listed in Table 6 shows that
the dialdehydes 16, 17 and 18 were also compatible
with the reaction conditions, and the corresponding
products 24a–c were obtained in good yields.
Notably, the established protocol is also applicable
to the synthesis of triphenylenevinylene-linked bis(di-
pyrromethanes) 25a–c through the condensation reac-
tion between triphenylenevinylene-linked dialdehydes
(19–21) and pyrrole (Table 7). During the study into
Entry
Dialdehyde
R1
R2
H
OC4H9
OC10H21
1
2
3
19
20
21
OC10H21
OC10H21
OC10H21
With these libraries of dialdehydes in hand, our at- the synthesis of triphenylenevinylene-linked bis(dipyr-
tention shifted to the synthesis of the corresponding romethanes), we found that such dialdehydes were
bis(dipyrromethanes).
relatively insoluble in neat pyrrole at room tempera-
We extend the strategy of synthesizing dipyrrome- ture. However, raising the reaction temperature from
thanes to the preparation of bis(dipyrrometh- room temperature to 508C could significantly increase
ACHTUNGTRENNUNG
anes).[7e,15] All of the bis(dipyrromethanes) reported the solubility of the starting materials, which facilitat-
in this paper were synthesized efficiently under identi- ed the condensation reaction.
fied conditions via condensation of arylene-linked di-
With these novel bis(dipyrromethanes) in hand, we
aldehydes and pyrrole. The following are the details attempted to synthesize novel multiporphyrin arrays
for the reaction conditions: under argon; a 150:1 ratio by the “2+2” method. Diporphyrin 27 was successful-
of pyrrole:dialdehyde; 0.1 equivalent of InCl3 as cata- ly produced in 12.3% yield through condensation of
lyst; at room temperature for 2 h. All reported yields bis(dipyrromethanes) 22d with a dipyrromethane-di-
were based on the weight of the isolated bis(dipyrro- carbinol compound derived from 26 via a modified
methanes) and the purity was measured by HLPC.
procedure (Scheme 3).[6] This yield of 27 was a bit
Firstly, this method was applied to the synthesis of higher than a previous result.[6]
a range of phenylene-linked bis(dipyrromethanes)
In conclusion, a series of variously functionalized
bearing various functional groups in the phenyl rings. phenylene-linked, biphenylene-linked, triphenylene-
As shown in Table 4, the condensation reaction oc- linked, and triphenylenevinylene-linked dialdehyde
curred smoothly for both electron-deficient (2, 3) and derivatives were synthesized, and the corresponding
electron-rich (4, 5, 6) substrates, to give 22b, 22c and libraries of novel bis(dipyrromethanes) were prepared
22d, 22e, 22f, respectively. In the case of 22c, precipi- by InCl3-catalyzed condensation of those dialdehydes
tation was observed during the reaction due to the and pyrrole. This protocol has several advantages
low solubility of the target product in pyrrole and sol- over published procedures for the synthesis of a large
vents applied, resulting in the relatively low yield of variety of bis(dipyrromethanes), such as high efficien-
77%.
cy and great tunability of the linkers, especially useful
Bis(dipyrromethanes) with a biphenylene-linker for the synthesis of multiporphyrin arrays. This work
23a–d were successfully synthesized by the same will provide a useful means for the construction of
method. The results are listed in Table 5.
novel multiporphyrin arrays with targeted functionali-
Adv. Synth. Catal. 2010, 352, 3083 – 3088
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Hongbin Zhao et al.
UPDATES
Table 5. Synthesis of biphenylene-linked bis(dipyrromethanes).
Dialdehyde
Bis(dipyrromethanes)
R1
R2
Time [min]
Yield [%]
7[a]
10
12
15
23a
23b
23c
23d
H
H
H
CH3
H
120
120
120
120
88
83
86
79
CH3
CH3
OC4H9
[a]
Compound 7 was produced according to a literature procedure.[16]
Table 6. Synthesis of terphenylene-linked bis(dipyrromethanes).
Dialdehyde
Bis(dipyrromethanes)
R1
R2
Time [min]
Yield [%]
16
17
18
24a
24b
24c
CH3
CH3
OC10H21
H
CH3
H
120
120
120
73
78
75
Table 7. Synthesis of triphenylenevinylene-linked bis(dipyrromethanes).
Dialdehyde
Bis(dipyrromethanes)
R1
R2
Time [min]
Yield [%]
19
20
21
25a
25b
25c
OC10H21
OC10H21
OC10H21
H
90
90
90
85
82
78
OC4H9
OC10H21
ties, due to the diversity of the well-designed linkers Experimental Section
in the critical precursor compounds bis(dipyrrome-
thanes).
Further studies into the synthesis of bis(dipyrrome-
thanes) with other functional groups and the construc-
tion of multiporphyrin arrays with numerous porphy-
rin units from these obtained bis(dipyrromethane) de-
rivatives via simultaneous condensation–cyclization–
polymerization are in progress in our laboratory.
General Remarks
1H NMR and 13C NMR spectra were recorded on a Bruker
Avance spectrometer (400 and 100 MHz, respectively).
Melting points are uncorrected. The purities of all key inter-
mediates and final products were examined by HLPC analy-
sis. HLPC analysis was carried out with a P680A instrument
using a C18 column (5 mm, 150 mmꢂ4.6 mm) with detection
wavelengths of 220 nm. The solvent was acetonitrile/water
(flow rate=1 mLminÀ1). The gradient program proceeded
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Efficient Synthesis of Novel Bis(dipyrromethanes) with Versatile Linkers
cane during the alkylation. Product 4 was obtained as a
yellow solid in 92% yield; mp 87–898C (lit. 84–868C).[17]
1H NMR (400 MHz, CDCl3): d=10.52 (s, 2H), 7.43 (s, 2H),
4.08–4.11 (t, 4H), 1.80–1.86 (m, 4H), 1.48–1.54 (m, 4H),
0.97–1.01 (t, 6H); 13C NMR (100 MHz, CDCl3): d=189.10,
155.17, 129.34, 111.66, 68.95, 31.04, 19.15, 13.64. MALDI-
TOF-MS m/z=278.43 (obs.), calcd. avg. mass: 278.34.
Representative Procedure for the Synthesis of
Phenylene-Linked Bis(dipyrromethanes): 2,5-
BisACTHNUGRTENUNG(butoxy)-1,4-bis(dipyrromethan-5-yl)benzene (22d)
By modifying a literature procedure,[7e] the reaction was
conducted with dialdehyde 4 (0.28 g, 1.0 mmol) and pyrrole
(10.4 mL, 0.15 mol) at room temperature under argon. After
stirring for 2 h, powdered NaOH (0.2 g, 5 mmol) was added
and the reaction mixture was further stirred for 30 min. The
mixture was filtered. Excess pyrrole was removed by distilla-
tion under reduced pressure and the resulting yellow solid
was treated with hexanes (10 mL). The solvent was removed
under reduced pressure, affording a precipitate. The crude
residue was dissolved in a small amount of CH2Cl2, and pu-
rified by column chromatography on silica gel (petroleum
ether/CH2Cl2/ethyl acetate=4:2:1) to give 22d as a pale
brown solid; yield: 0.46 g (90%); 98.15% purity by HLPC;
mp 148–1508C. 1H NMR (400 MHz, CDCl3): d=8.25 (br,
4H), 6.74 (s, 2H), 6.66 (m, 4H), 6.13 (m, 4H), 5.93 (m, 4H),
5.66 (s, 2H), 3.73–3.76 (t, 4H), 1.54 (m, 4H), 1.27–1.32 (m,
4H), 0.86–0.89 (t, 6H); 13C NMR (100 MHz, CDCl3): d=
150.5, 132.5, 130.7, 116.6, 115.2, 108.2, 106.6, 69.4, 39.1, 31.5,
19.2, 13.8; LC-MS (%): m/z=510.6 (100), calcd.: 510.30;
HR-MS: m/z=510.2990, calcd. for C32H38N4O2 [M]+:
510.2995.
Representative Procedures for the Synthesis of
Diporphyrin via Bis(dipyrromethanes): 5-(4-
Bromophenyl)dipyrromethane (CAS: 159152-11-1)
By modifying a literature procedure,[7e] a mixture of 4-bro-
mobenzaldehyde (1.85 g, 10 mmol) and pyrrole (52 mL, 0.75
mol) was treated with InCl3 (0.2 g, 1.0 mmol) at room tem-
perature under argon. After stirring for 4 h, powdered
NaOH (4.0 g, 100 mmol) was added and the reaction mix-
ture was stirred for 45 min. The mixture was filtered. Excess
pyrrole was removed by distillation under reduced pressure
and the resulting yellow solid was treated with hexanes. The
solvent was removed under reduced pressure, affording a
Scheme 3. Synthesis of diporphyrin via bis(dipyrrome-
thanes).
from 60% acetonitrile to 90% acetonitrile over 25 min with
hold at 90% acetonitrile over 6 min. Mass spectra were ob-
tained via matrix-assisted laser desorption ionization mass
spectrometry (MALDI-MS) without a matrix. Silica gel
(40 mm average particle size) was used for column chroma-
tography. Thin layer chromatography was performed by
using SiliCycle Silica Gel 60 F254 TLC plates and visualized
with ultraviolet light. Compounds purchased from Alfa-
Aesar were used without further purification. Pyrrole was
distilled from CaH2. THF and toluene were freshly distilled
from CaH2.
precipitate. Recrystallization (CH3CH2OH/H2O) gave
a
light yellow solid; yield: 2.7 g (89%); mp 123–1258C (lit.
125.0–125.58C).[7e] 1H NMR (400 MHz, CDCl3): d=7.91 (br,
2H), 7.42–7.44 (d, 2H), 7.07–7.09 (d, 2H), 6.70 (s, 2H),
6.15–6.16 (d, 2H), 5.88 (s, 2H), 5.43 (s, 1H); 13C NMR
(100 MHz, CDCl3): d=141.30, 131.95, 131.71, 130.16, 120.85,
117.55, 108.62, 107.52, 43.49. MALDI-TOF-MS: m/z=
301.27 (obs.), calcd. avg. mass: 301.18.
5-(4-Bromophenyl)-1,9-bisACTHNUTRGENUGN(benzoyl)dipyrromethane (26)
Representative Procedure for the Synthesis of
Phenylene-Linked Dialdehydes: 2,5-BisACHTNUTRGNE(UNG butoxy)-
benzene-1,4-dialdehyde (4) (CAS: 564456-59-3)
By modifying a literature procedure,[6] a solution of 5-(4-
bromophenyl)dipyrromethane (3.01 g, 10 mmol) in dry tolu-
ene (200 mL) was treated with a solution of EtMgBr
(50 mL, 50 mmol, 1.0M in THF) under argon at room tem-
perature. After stirring for 60 min, a sample of C6H5COCl
It was produced by the same method as for the synthesis of
compound 6,[9] using 1-bromobutane instead of 1-bromode-
Adv. Synth. Catal. 2010, 352, 3083 – 3088
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3087

Hongbin Zhao et al.
UPDATES
(2.9 mL, 25 mmol) was added. After stirring for 3 h, the re-
action was quenched by adding saturated aqueous NH4Cl
(80 mL). The organic phase was separated, washed with
brine and dried over anhydrous Na2SO4. After removing the
toluene, the resulting crude product was purified by column
chromatography on silica gel (petroleum ether/CH2Cl2/ethyl
acetate=4:2:1), affording a brown solid; 1.25 g (25%); mp
(No: 7007735) and the Natural Science Foundation of Hunan
Province, China (No: 04JJ40013).
References
1
114–1168C. H NMR (400 MHz, CDCl3): d=11.36 (s, 2H),
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7.74–7.78 (m, 4H), 7.45–7.52 (m, 4H), 7.38–7.45 (m, 6H),
6.58–6.59 (m, 2H), 5.98 (m, 2H), 5.65 (s, 1H); 13C NMR
(100 MHz, CDCl3): d=184.64, 140.30, 139.41, 138.16, 131.92,
131.74, 131.17, 130.45, 129.43, 128.08, 121.46, 120.87, 111.19,
44.32; MALDI-TOF-MS: m/z=509.00 (obs.), calcd. avg.
mass: 509.39.
2,5-Dibutoxy-1,4-bisACTHNUTRGNE[NUG 10-(4-bromophenyl)-5,15-
diphenylporphin-20-yl]benzene (27)
By modifying a literature procedure,[6] a solution of com-
pound 26 (0.509 g, 1.0 mmol) in dry THF/methanol (33 mL,
10:1) was treated with NaBH4 (1.513 g, 40 mmol) at room
temperature for 4 h. The reaction mixture was poured into a
mixture of saturated aqueous NH4Cl (80 mL) and CH2Cl2
(80 mL). The organic phase was separated, dried over anhy-
drous Na2SO4 and concentrated to dryness. The resulting di-
pyrromethane-dicarbinol was dissolved in CH2Cl2 (200 mL)
and
2,5-bisACHTUNGTRENNUNG(butoxy)-1,4-bis(dipyrromethan-5-yl)benzene
ACHTUNGTRENNUNG(22d) (256 mg, 0.5 mmol) was added under argon at room
temperature. After a homogenous solution was obtained,
InCl3 (0.238 g, 0.81 mmol) was added and the reaction mix-
ture was stirred at room temperature for 24 h. Chloranil
(1.266 g, 5.14 mmol) was added and stirring was continued
for 7 h. The mixture was passed through column chromatog-
raphy (alumina, CH2Cl2) and eluted with CH2Cl2 until the
eluant was no longer dark. The collected eluant was concen-
trated. The resulting crude product was purified by column
chromatography on silica gel (CH2Cl2/hexanes=3:1). Re-
crystallization (CHCl3/CH3OH) gave a purplish black solid;
yield: 90 mg (12.3%); mp >2808C. 1H NMR (400 MHz,
CDCl3): d=9.33 (m, 4H), 9.03 (m, 4H), 8.91 (m, 4H), 8.86
(m, 4H), 8.30 (m, 8H), 8.14–8.09 (m, 4H), 8.05 (s, 2H),
7.93–7.91 (m, 8H), 7.83 (m, 8H), 3.91–3.88 (t, 4H), 0.98–
0.96 (m, 4H), 0.50–0.48 (m, 4H), 0.20–0.16 (t, 6H), À2.62 (s,
4H); 13C NMR (100 MHz, CDCl3): d=168.16, 157.59,
151.06, 141.24, 140.38, 139.60, 134.89, 134.87, 133.65, 133.55,
131.51, 130.55, 130.24, 128.92, 128.10, 127.46, 126.81, 125.77,
121.47, 119.90, 119.26, 117.96, 117.55, 115.56, 68.46, 28.69,
17.44, 12.13; MALDI-TOF-MS: m/z=1453.36 (obs.), calcd.
avg. mass: 1453.36.
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Supporting Information
Experimental procedures and H-, 13C NMR and mass spec-
tra for all the other unknown compounds or some important
known intermediates obtained via modified procedures are
available as Supporting Information.
1
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Acknowledgements
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Adv. Synth. Catal. 2010, 352, 3083 – 3088