Facile access to a series of large polycondensed pyridazines and their utility for the supramolecular synthesis of coordination polymers

Article abstract of DOI:10.1039/c2cc31770b

Domino cyclization of ketoenols and hydrazine leads to a series of polycondensed pyridazines, which reveal potential as rigid N-donor multidentate ligands for supramolecular synthesis of open coordination polymers.

Full text of DOI:10.1039/c2cc31770b

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Facile access to a series of large polycondensed pyridazines and their
utility for the supramolecular synthesis of coordination polymersw
a
a
b
a
Konstantin V. Domasevitch,* Pavlo V. Solntsev, Harald Krautscheid, Iryna S. Zhylenko,
c
c
Eduard B. Rusanov and Alexander N. Chernega
Received 9th March 2012, Accepted 13th April 2012
DOI: 10.1039/c2cc31770b
Domino cyclization of ketoenols and hydrazine leads to a series
of polycondensed pyridazines, which reveal potential as rigid
N-donor multidentate ligands for supramolecular synthesis of
open coordination polymers.
appropriate ketoenol and hydrazine. A suitable prototype for
this protocol may be recognized in the synthesis of hexa-
hydrocinnolino[5,4,3-cde]cinnoline, which was known for
decades only as
a
,3-cyclohexanediones, implying postulation of intermediate
specific reaction of hydrazine and
1
1
1
0
0-membered cyclic bis-azine.
The fact that the reaction of hydrazine with ketoenols could
Recent years have been marked by rapidly growing interest in
1
derivatives of pyridazines, as potent pharmaceuticals, agro-
2
possess much wider significance for the synthesis of pyrida-
zines suggests examination of two closely related vinylogous
ketoenols 1a and 1b (Scheme 1). These model substrates with a
rigidized structure of the carbocyclic linkage could presumably
allow the generation of the symmetrical polycondensed
species.z Products of their reaction with hydrazine, isolated
in reasonable yields after slow air-oxidation of the reaction
mixtures, are deep-red crystalline helicene-like polycycles.
They feature a central pyridazine ring bearing two c- and
e-edge annelated carbocyclic moieties. The distribution
chemicals, materials for liquid crystals, p-deficient dipolar
systems for electron transfer, electronic and electrooptic
3
devices, anion receptors, building blocks for supramolecular
4
5
6
synthesis and versatile reaction substrates. New advances in
the field are largely complicated by the synthetic accessibility
of the pyridazines, preparative chemistry of which actually
presents only two general methods: reaction of 1,4-diketones
with hydrazine and inverse electron demand cycloadditions of
7
,2,4,5-tetrazines, both of which are inefficient for the development
1
of the especially valuable fused ring systems.
˚
of short CQC (1.342(3)–1.349(4) A) and longer C–C
New pathways to polycondensed pyridazines are feasible
when considering the reactivity of hydrazine towards 1,4-diketone
˚
1.438(4)–1.464(3) A) bonds is indicative of conjugation
(
(
1,4-diketoimine) substrates, as intermediates of the classical
Piloty–Robinson synthesis. The cyclization to the dihydro-
pyridazine, instead of the usual pyrrole product, can be
anticipated under very mild reaction conditions avoiding
acid-catalyzed tautomerization and diaza-Cope rearrange-
8
ment of the initial ketazine at elevated temperatures or the
9
related rearrangements promoted by strong bases. The ease of
the above tautomerization is particularly prevalent.
In the present work we demonstrate how the route of the
Piloty–Robinson cyclization may be directed towards assembly
of the pyridazine frame by utilizing highly-enolized substrates.
This allows us to combine every local step of the reaction
under ambient conditions and to elaborate a one-pot synthesis
of condensed pyridazines by the very simple reaction of the
a
Inorganic Chemistry Department, Kyiv University, Volodimirska Str. 64,
Kyiv 01033, Ukraine. E-mail: dk@univ.kiev.ua
Institut fu¨r Anorganische Chemie, Universita¨t Leipzig,
Johannisallee 29, D-04103 Leipzig, Germany
Institute of Organic Chemistry, Murmanskaya Str.4, Kyiv 253660,
Ukraine
b
c
w Electronic supplementary information (ESI) available: Details of
multi-stage organic syntheses, crystal structure determination and
thermal studies. CCDC 870944–870948. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c2cc31770b
Scheme 1 Synthesis of fused pyridazines by domino condensation of
cyclic ketoenols and hydrazine.
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Fig. 1 Helicene-like conjugated pyridazine–bis-hydrazones formed from vinylogous ketoenols 1a (A) and 1b (B) and the final product of the
4
domino cyclization featuring the aromatic pyridazino[4,5-g]phthalazine frame (N cor) (C).
+
Cu ions, which commonly exhibit a pronounced affinity
between the pyridazine and hydrazone groups that occurs via
the chain of alternating single and double bonds:
1
2
towards electron deficient N-heteroaromatic species.
Black-red crystals of [Cu (N
cor)]ꢀSolv (4: X = I, Solv =
CH ; 5: X = Cl, Solv = 4CH CN) were obtained
CNꢀCHCl
C–(CQC)
n
–CQN–NH
2
(2a: n = 1; 2b: n = 2).y
2
X
2
4
Further cyclization of such products is of significant
interest as a source of a library of large polycondensed
bifunctional pyridazines. This was examined with the readily
accessible substrate 2a: crystal structure data suggest
3
3
3
I
from Cu halides using a layering technique. The compounds
adopt a 3D framework structure involving the copper(I)
chloride (iodide) portion in the form of four-fold helices.
The organic ligands, as geometrically proper and rigid tetra-
dentates, bridge the adjacent tetrahedral Cu ions along the
chain and extend the coordination geometry in two ortho-
gonal directions (Fig. 2) giving a desired and very elegant
architecture in the form of a tetragonal framework with
the disposition of ethylene bonds in such proximity
˚
(
C4ꢀ ꢀ ꢀC14 3.30 A) that the cyclization could be expected as
a photochemical reaction followed by air-oxidation and fast
cyclization of the bis-hydrazone intermediate. Indeed, stirring
of an ethanol suspension of 2a when exposed to direct sunlight
˚
large channels along the c axis (diameter ca. 6.5 A). Being
(
no reaction was observed in the dark) led to the unique
coronene-like product (3, N
isolable yield.
4
corꢀ2H
2
O), in almost quantitative
almost uniform in the local coordination geometry (4: Cu–N
2.070(4) ꢁ 2; Cu–I 2.6184(7) ꢁ 2; 5: Cu–N 2.046(3), 2.061(4);
˚
Cu–Cl 2.3617(15), 2.3644(15) A) as well as in the entire shape
The latter reveals annelation of aromatic and two alicyclic
decalin fragments. An appreciable differentiation of bond
and metrics of the frameworks, the compounds exhibit a
special and peculiar type of supramolecular isomerism based
upon homochiral alignment (5) or combination of the helices
of opposite chirality (4). Considering Cu ions and the organic
ligands as four-connected nodes, the iodide topology is a
lengths (N–N 1.3992(18); av. C–N 1.305(2) and av. C–CN
˚
1
.438(2) A) is in agreement with the bis-azine structure of the
central pyridazino[4,5-g]phthalazine frame (Fig. 1). Such
3
species may find use as photochromic materials, molecular
2
2
2
2
2
building blocks for functional organic co-crystals and
especially as nanosized N-donor tectons for synthesis of
binodal ‘‘asf’’ net (point symbol {3 .8.9 .10}
2
{3 .8 .9 };
), while the chloride framework is
a uninodal semiregular chiral net ‘‘lcv’’ with Schlafli point
1
3
2 6
structural type ZrGe O
1
coordination polymers. The latter was explored for the soft
1
¨
Fig. 2 Interconnection of (CuI)
n
helices by tetradentate ligands N
4
cor. Note how the inorganic and organic components are complementary in the
(N
3
view of coordination functionality and molecular shape (A). Space-filling representations of the isoreticular frameworks of [Cu
2
I
2
4
cor)]ꢀCH
3
CNꢀCHCl
11
3
(
4) (B) and [Cu
2
I (N
2 4
pyr)]ꢀ0.5CHCl
(C) (solvent molecules are omitted), which depicts a progressive increase in the channel size and micropore
volume.
Chem. Commun.
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3
mL of acetonitrile and 5 mL of CHCl
product (39 mg, 90%) grew on the walls of the tube as the solutions
interdiffused in a 15–20 d period. [Cu Cl (N CN (5) was
cor)]ꢀ4CH
synthesized in a similar fashion in a mixture of anhydrous CH CN and
CH Cl , starting with freshly prepared CuCl (yield: 70%).
3
. Large black-red prisms of the
2
2
4
3
3
2
2
y Crystallographic measurements were made at 173 K using a Bruker
˚
APEX-II diffractometer (Mo-Ka, l = 0.71073 A). Crystal data for
2
(2a)ꢀEtOHꢀH
2 56 12 2
O: C42H N O , M = 760.99, triclinic, space group
P 1% , a = 10.7110(10), b = 11.5603(11), c = 18.6159(16) A, a =
˚
3
˚
7
6.538(6)1, b = 90.023(6)1, g = 62.401(7)1, V = 1970.9(3) A , Z = 2,
ꢂ3
D
calc = 1.282 g cm , 15 474 reflections measured, 7548 unique
Scheme 2 Extension of the coordination bridge by linear annelation.
(
0
R
int = 0.060). R
.140. For 2bꢀEtOH: C30
/c, a = 17.8207(6), b = 6.1397(2), c = 24.7531(8) A, b =
1
[4553 with I > 2s(I)] = 0.056, wR
2
(all data) =
38 6
H N
O, M = 498.66, monoclinic, space
2
symbol {3 .10 }. The latter is a case of spontaneous resolution
4
˚
group P2
100.4510(10)1, V = 2663.40(15) A , Z = 4, Dcalc = 1.244 g cm
6 160 reflections measured, 5056 unique (Rint = 0.036). R [3479 with
I > 2s(I)] = 0.070, wR (all data) = 0.214. For N O (3):
corꢀ2H
, M = 350.42, monoclinic, space group P2 /c, a =
5.0227(5), b = 13.5312(14), c = 12.4146(15) A, b = 94.498(8)1,
1
1
4
˚
3
ꢂ3
,
from apparently achiral building blocks.
2
1
Desolvation of 4 occurs with 4.9% mass loss at 60–160 1C
CH CN, calcd: 4.8%) and 13.7% at 180—220 1C (CHCl ,
calcd: 14.0%). The latter stage proceeds with loss of crystallinity,
2
4
2
(
3
3
C
20
H
22
N
4
O
2
1
˚
3
ꢂ3
˚
as was indicated by thermo-XRPD patterns.
The iodide complex 4 and the prototype compound based
V = 841.14(16) A , Z = 2, Dcalc = 1.384 g cm , 5454 reflections
measured, 1692 unique (Rint = 0.027). R [1013 with I > 2s(I)] =
.043, wR (all data) = 0.118. For [Cu (N CNꢀCHCl (4):
cor)]ꢀCH
22Cl Cu , M = 855.69, tetragonal, space group I4 /amd,
1
0
C
2
2
I
2
4
3
3
1
1
upon the simpler pyridazino[4,5-d]pyridazine N
are illustrative of topologically identical, isoreticular (space
group I4 /amd) open frameworks with the tuneable metrics
imprinted by the effective sizes of the organic connectors. The
4
pyr (Scheme 2)
23
H
3
2
I
2
N
5
1
3
˚
˚
a = b = 22.3792(2), c = 13.1261(3) A; V = 6573.93(17) A , Z = 8,
Dcalc = 1.729 g cm , 13 376 reflections measured, 1779 unique
(
ꢂ3
1
Rint = 0.061). R
.125. For [Cu
1
[1054 with I > 2s(I)] = 0.046, wR
Cl (N CN (5):
cor)]ꢀ4CH
2
(all data) =
2 8
30Cl Cu N ,
0
M = 676.58, tetragonal, space group P4 2 2 (P4 2 2), a = b =
2
2
4
3
C
28
H
2
1
1
[
Cu
2
I
while for [Cu
2
(N
4
pyr)] framework provides only 27.2% free space,
(N cor)] the calculated solvent accessible area is
3
1
1 1
3
15.9327(9), c = 12.4522(10) A; V = 3161.0(4) A , Z = 4, Dcalc
˚
˚
I
2 2
4
=
.422 g cm , 17 481 reflections measured, 3407 unique (Rint = 0.050).
ꢂ3
1
as large as 51.9% of the crystal volume (48.6% for the chloride
analogue). We anticipate that the porosity of the structure
could be further greatly enhanced by utilization of more
lengthy polycycles, presumably accessible by condensation of
ketoenols (i.e. 1b) and hydrazine. It is worth mentioning that
1 2
R [2109 with I > 2s(I)] = 0.038, wR (all data) = 0.102. The refined
Flack x parameter converged to a value of 0.52(3), indicating a
racemic twinning.
1
2
C. G. Wermuth, Med. Chem. Commun., 2011, 2, 935.
V. E. Amoo, C. R. Harrison, G. P. Lahm, P. D. Lowder, T. M.
Stevenson, J. K. Long, R. Shapiro, R. W. March, D. E. Allen,
M. D. Richmond, W. A. March, G. Chun, M. P. Folgar and
S. M. Griswold, Synthesis and Chemistry of Agrochemicals VI,
ACS Symp. Ser., 2001, 800, 156.
(
CuX)
shape-complementary packing constituting impenetrable
‘walls’’ of the channels (Fig. 2A). The latter could be relevant
n
helices and cyclohexane sides of the ligands afford a
‘
for preventing interpenetration of the identical frameworks
when approaching even a higher porosity of the solid.
In summary, our study is important for developing innovative
synthetic protocols towards fused pyridazine systems. The
present simple procedure will find wider applications facilitating
chemical access to special types of pyridazines, such as poly-
condensed, sterically strained and conjugated species. Our
findings provide a convenient entry into a series of novel
geometrically rigid ‘‘building blocks’’ for crystal design, in
particular for the synthesis of open framework coordination
polymers with tuneable metrics.
3 S. Achelle, N. Ple
S. J. Cowling, A. W. Hall and J. W. Goodby, Chem. Commun.,
005, 1546.
´
and A. Turck, RSC Adv., 2011, 1, 364;
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I. A. Gural’skiy, P. V. Solntsev, H. Krautscheid and K. V.
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A. N. Chernega and J. A. K. Howard, Dalton Trans., 2007,
3
893–3905.
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U. Beckmann and S. Brooker, Coord. Chem. Rev., 2003, 245, 17;
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7
8
The authors acknowledge support from Deutsche Forschungs-
gemeinschaft, grant UKR 17/1/06 (HK and KVD).
Notes and references
9
Y. Tamaru, T. Harada and Z. Yoshida, J. Org. Chem., 1978,
43, 3370; Z. Yoshida, T. Harada and Y. Tamaru, Tetrahedron
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9,10
z Condensation of ketoenols and hydrazine: a solution of D -octaline-
,7-dione 1a (2.20 g, 13.4 mmol) in 80 mL of dry ethanol was added
dropwise to 4.0 mL of N O (82 mmol) in 20 mL of dry ethanol
2
2
H
4
ꢀH
2
10 J. K. Stille and R. Ertz, J. Am. Chem. Soc., 1964, 86, 661;
J. K. Stille, J. M. Unglaube and M. E. Freeburger, J. Am. Chem.
Soc., 1968, 90, 7076.
11 P. V. Solntsev, J. Sieler, H. Krautscheid and K. V. Domasevitch,
Dalton Trans., 2004, 1153.
12 M. Munakata, L. P. Wu and T. Kuroda-Sowa, Advances in
Inorganic Chemistry, 1999, vol. 46, p. 173.
13 O. Delgado-Friedrichs, M. O’Keeffe and O. M. Yaghi, Acta
Crystallogr., Sect. A: Fundam. Crystallogr., 2003, 59, 515.
with stirring and cooling to 0 1C. After 12 h, the deep-red solution was
evaporated under reduced pressure to a volume of 30 mL and then left
in an open flask for 20–25 d at r.t. Deep-red 2a (solvate with ethanol
and water) was obtained in a yield of 1.79 g (70%). Further, this
dihydrazone (1.32 g, 3.5 mmol) was stirred in 40 mL of 95% ethanol in
an open flask when being exposed to direct sunlight until total
dissolution was observed within a period of 3–4 d. The clear solution
was slowly evaporated at r.t. to a volume of 6–7 mL and the pale-
yellow needles of N
dried (1.13 g, 93%). Complex [Cu
prepared by layering a solution of 19.0 mg (0.1 mmol) CuI in 4 mL
of acetonitrile over a solution of the ligand (17.5 mg, 0.05 mmol) in
4
corꢀ2H
2
O were filtered off, washed with ether and
(N (4) was
14 B. Gil-Herna
C. Janiak, Chem. Commun., 2010, 46, 8270; B. Gil-Herna
J. K. Maclaren, H. A. Hoppe, J. Pasan, J. Sanchiz and C. Janiak,
CrystEngComm, 2012, 14, 2635.
´
ndez, H. A. Ho
¨
ppe, J. K. Vieth, J. Sanchiz and
I
2 2
4
cor)]ꢀCH
3
CNꢀCHCl
3
´
ndez,
¨
´
This journal is c The Royal Society of Chemistry 2012
Chem. Commun.