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Dihydropyrazolopyridine and Bis(dihydroindolizine)ЧNovel Mono- and Bifunctional Photochromic Systems.

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ature. In the case of 3, the disorder can be described to a
good approximation in terms of a model in which half of
the As atoms occupy position 1 of the ring and the other
half position 4 of the ring (R,=0.086 for 424 reflections).
The chromium atom is located 25 pm from a crystallographic center of symmetry, so that the two alternative orientations of the complex are slightly displaced from each
other. It is therefore impossible to infer structural details
of the coordinated arsabenzene rings. However, from the
positions of the As atoms it can be concluded that either
the cis- or the trans-eclipsed form is present, and, from the
maximum Cr-As distance of 252 pm that genuine $-coordination prevails." 'I
A first indication of the electronic structure of 3 is provided by the ESR spectra of the radical cation 3'@:
Whereas the data obtained for 3" in fluid solution (dimethylformamide (DMF)/CHCl3= 1 : 1, 30"C, (g)= 1.9892,
a(53Cr)= 19.3 G, ligand hyperfine structure only partially
resolved) are consistent with the parameters of bis(q6-arene)chromium(d5) cations,["] the spectrum of 3
recorded in rigid solution (DMF/CHC13= 1 : I, - 135"C, g n =
1.9730, g L = 1.9980, A,(53Cr)=20 G) shows a g-anisotropy, typical for his($'-arene)chromium anion^.^'^] In the latter, an MO with dominant n-ligand character is singly occupied. The similar g-anisotropy thus suggests that-in
contrast to cations of the corresponding carbocyclic arene
complex-the singly occupied HOMO in 3 O @ has considerable ligand character.
''
Received: December 30, 1985;
revised: March 17, 1986 [Z 1600 IE]
German version: Angew. Chem. 98 (1986) 562
CAS Registry numbers:
1, 289-31-6; 3, 101934-66-1; 30°, 101934-67-2; Cr, 7440-47-3
[ I ] C. Elschenbroich, J. Schneider, H. Prinzbach, W.-0. Fessner, Organometallics, in press.
[2] a) G. E. Herberich, G. Greiss, H. F. Heil, J. Miiller, J . Chem. SOC.Chem.
Commun. 1971. 1328; b) G. E. Herberich, G. Greiss, Chem. Ber. 105
(1972) 3413; c) G. E. Herberich, M. J. Becker, G. Greiss, ibid. 107 (1974)
3780; d) A. J. Ashe 111, E. Myers, P. Shu, T. V. Lehmann, J . Am. Chem.
SOC.97 (1975) 6865; e) L. M. Simmons, P. E. Riley, R. E. Davies, J. J.
Lagowski, rbid. 98 (1976) 1044; f) P. E. Riley, R. E. Davies, Inorg. Chem.
15 (1976) 2735; g) A. J. Ashe 111, W. Butler, H. F. Sandford, J. Am.
Chem. SOC.101 (1979) 7066; h) binary transition metal complexes of the
h"-phosphorin anions 1-R-2,4,6-Rj-CrH2PQ undergo q'-coordination
and are to be regarded as 2,6-bridged open metallocenes: T. Dave, S .
Berger, E. Bilger, H. Kaletsch, J. Pebler, J. Knecht, K. Dimroth, Orgunometallics 4 (1985) 1565; G. Baum, W. Massa, ibid. 4 (1985) 1572; i) an
q6-bonded phosphabenzene derivative is present in the mixed sandwich
F. Nief, C. Charrier, F.
complex [(1,3,5-Phl-q6-CsH2P)(qs-CsHs)Mn]:
Mathey, M. Simalty, J . Organomet. Chem. 187(1980) 277; J. Fischer, A.
De Cian, F. Nief, Acta Crystallogr. Sect. 8 3 7 (1981) 1067.
[3] a) J. Deberitz, H. Noth, Chem. Ber. 103 (1970) 2542; 106 (1973) 2222; J.
Organornet. Chem. 49 (1973) 453; b) H. Vahrenkamp, H. Noth, Chem.
Ber. 105 (1972) 1148; 106 (1973) 2227; H.-G. Biedermann, K. Of&. J.
Tajtelbaum, Z . Naturforsch. B: Anorg. Chem. Org. Chem. 31 [ 1976)
321.
141 a) A. J. Ashe 111, Top. Curr. Chem. 105 (1982) 125; b) R. V. Hodges, J. L.
Beauchamp, A. J. Ashe 111, W:T. Chan, Organometallics 4 (1985) 457.
151 A. J. Ashe 111, J. C. Colburn, J . Am. Chem. SOC.99 (1977) 8099.
161 Procedure: The vapors of arsabenzene 1 (3 g, 36 mmol) [7] and chromium (0.3 g, 5.8 mmol) were cocondensed over a period of 1.5 h onto the
walls of a n evacuated, cooled ( - 196°C) reaction vessel. After warming
to room temperature under N2, the dark red co-condensate was taken up
in tetrahydrofuran and the solution filtered over silanated silica gel. The
solvent and unchanged 1 , which can be recovered in this way, were removed in a high vacuum. Recrystallization of the residue from toluene
afforded 3 in the form of reddish-black, analytically pure crystals (yield:
290 mg (0.87 mmol), 15% referred to vaporized Cr). M.p. 253OC (dec.);
MS (El, 70 ev): r n / z 332 (26%, Me),192 (39%, MO-L), 140 (58%. L"),
52 (100% "Cr').
[7] A. J. Ashe 111, W.-T. Chan, J. Org. Chem. 44 (1979) 1409.
IS] M. Wiinsch, C. Elschenbroich, unpublished.
572
0 VCH Verlagsgesellschaji mbH. 0-6940 Wemherm, 1986
191 'H-NMR data of 5 : 6=9.6 (H-2,6), 7.8 ( H - 3 3 , 7.5 (H-4) [5]; cf. also A.
J. Ashe 111, R. R. Sharp, J. W. Tolan, J . Am. Chem. Soc. 98 (1976)
5451.
[lo] D. R. Wilson, R. D. Ernst, T. H. Cymbaluk, Organometallics 2 (1983)
1220.
[ I 11 Other Cr-As distances: 252 pm in [(CO),C~AS(M~)~MII(CO)~]
(H. Vahrenkamp, Chem. Ber. 105 (1972) 1486), 238 pm in [C6H5As(Cr(CO)5J2J
(G. Huttner, J. von Seyerl, M. Marsili, H.-G. Schmid, Angew. Chem. 87
(1975) 455; Angew. Chem. I n [ . Ed. Engl. 14 (1975) 434).
[I21 C. Elschenbroich, R. Mockel, U. Zenneck, D. Clack, Ber. Bunsenges.
Phys. Chem. 83 (1979) 1008.
I131 C . Elschenbroich, E. Bilger, J. Koch, J. Weber, J. Am. Chem. Soc. 106
(1984) 4297, and references cited therein.
Dihydropyrazolopyridine and Bis(dihydroindo1izine)Novel Mono- and Bifunctional Photochromic
Systems**
By Heinz Diirr,* Charles Schommer, and
Thomas Miinzmay
Dedicated to Professor Heinz A. Sraab on the occasion of his
60th birthday
Photochromic systems have long claimed worldwide interest."] They are not only of great importance in fundamental research but also in practice, where they find application as light-filters, chemical actinometers, silver-free
materials for display devices in reprotechnology and more
recently in computer chips."' We recently reported on a
photochromic system based on a 1,5-electrocyclization of
spir~dihydroindolizine.~'~
The aim of our present work is to
prepare new systems that can undergo 1,5-electrocyclizations as well as molecules containing two chromophores.
We now report on the extraordinary reactivity of l-pyridinioamides ("pyridin-N-imines") 1 towards pentafulvenes such as 2. The deep-colored betaines initially
formed are converted in a 1,5-electrocyclic reaction into
the novel dihydropyrazolo[l,5-a]pyridines 4 ; these are the
first dihydropyrazole-based photochromic systems (Type
2,3-systems"').
For the synthesis of 4, the N-imines 1 were generated
from the corresponding N-aminopyridinium
with
potassium carbonate in anhydrous dimethylformamide
and allowed to react directly with 2 without prior isolati0n.1~~1
The deep-red to violet products transform within a few
hours into the yellow title compounds 4, whose structure
2
3
A . dis.
d
' h v , con.
E=COOMe
/--u
4
[*] Prof. Dr. H. Diirr, DipLChem. C . Schomrner, Dipl.-Chem. T . Miinzmay
Fachrichtung 14. I Organische Chemie der Universitat
D-6600 Saarbriicken I 1 (FRG)
[**I Photochromic Systems, Part 11. This work was supported by the
Deutsche Forschungsgemeinschaft and the Fonds der Chemischen In.
dustrie.-Part 10: H. Diirr, V. Bach, Tetruhedron Lett.. in press.
0570-0833/86/0606-0572$ 02.50/0
Angew. Chem. Int. Ed. Engl. 25 (1986) No. 6
Table I . Some data of the dihydropyrazolo[l,5-a]pyridines4 ( U V / V l S data:
see Table 2: for ' H - N M R of 4a see 151).
R
Yield
In4
IR (KBr) [cm-'1
I;(C=O)
V(C=N)
M.p.
I"C1
hv
+
E
2 N2
~~
4d
("
67
30
94
35
4e
C'OPh
15
4a
4b
4c
H
C'H,
Ph
I54
150
I55
162
176
-
1505
1710
1700
1505
1518
1715
1702
1705
1650
E
I505
1510
-
a
7
a , X = H, H; b
=
a; c,
x
= -
R
was derived from the spectroscopic data (Table 1). The assignment of the ' H - N M R signals of the dihydropyridine
protons (H-3a to H-7)lS1was accomplished by double resonance experiments, by a ('H,'H)-COSY experiment, and
by comparison with the spectra of dihydroindolizines. The
structure of 4 could be further verified by l3C-DEPT spectroscopy and by a I3C,'H-correlated 2D-NMR experiment.-The structure of the intermediates 3 was elucidated by 'H-NMR of the long-lived betaine 3g. The conversion of 3 into 4 is a thermal disrotatory I,5-electrocyclic ring-closure.
-R
A
2
\hv
R
9
10 (10
r
Table 2. Some UV/VIS data o f 3 and 4, as well as kinetic data [a] for the
cyclization 3-4.
A,,,
3
a
b
C
d
e
Inml ( I g d
4
511
51 I
547
527
556
401 (3.95)
399 (3.96)
406 (3.96)
406 (3.96)
414 (3.81)
365 (3.80)
10' k [s
2.17
1.89
2 46
5.14
4.2 1
~
'1
TI/..
.-p{
Is1
320
367
282
135
165
R'
E
1
9'
R
[a] At 25°C in CH2C12
Table 2 shows the absorption maxima in the electronic
spectrum of the betaines 3 and the dihydropyrazolopyridines 4. The compounds 4 are converted in a photochemical controtatory 1,5-electrocyclic ring-opening reaction
into 3. The half-lives s,,,=In2/k are also listed in Table 2.
The compounds 3 and 4 , which can undergo reversible interconversion, thus form a novel photochromic system
whose central reaction is 1,5-electrocyclic ring-opening.
We also report on the novel dichromophoric bis(dihydroindolizines) 10. Based on the synthesis for monofunctional dihydroindolizines, the bifunctional 3H-pyrazoles 7
were generated first by 1,3-dipolar cycloaddition of the
bis(diazo) compounds 6 to acetylenedicarboxylates 5.[6".h1
The structure of 7 could be verified by 'H-NMR, IR, and
mass spectroscopy and by elemental analysis.
The bis(pyrazo1es) 7 are cyclic cis-azo compounds,
which can be converted photochemically with loss of nitrogen into cyclopropenes[6'1 (in ether, pyrex filter, Hg
high-pressure lamp HPK 125W; yield: 8a lo%, 8c 50%).
Recrystallization of the solvent-free residue (ether) afforded the bis(cyc1opropenes) 8, which showed the strong
IR bands characteristic for the cyclopropenes at 1850
cm-'. For the synthesis of the photochromic bis(dihydroindolizines) 10, the electrophilic bis(cyc1opropenes) 8
were allowed to react with six-membered N-heterocycles
in the molar ratio I : 2 (room temperature, ether). In all
cases the deep-colored betaines 9 (or 9') occurred as intermediates which thermally cyclized to the yellow bis(dihyAngen,. Cliem. In!. Ed. Engl. 25 (1986) No. 6
Table 3. Some data of the products 9 and 10 (10'). as well as some data for
comparison of 11 and 12.
9 , 10
R, R'
X
Y
a
Benzo
H, H
CH
b
Benzo
H, H
N
[%]
M.p.
["C]
A,n,*. [nm]
( C . lo-') [a]
9
10
13
210
4
180
577
(13) IbI
481
Yield
526
396
(14)
378
(16)
387
-
(15)
-
c [c]
11, 12
H, H
R, R'
X
N
Y
56
Yield
["/.I
a
Benzo
H, H
CH
52
b
Benzo
H, H
N
39
240
Am,,, [nml
(C-
C
H, H
-
N
74
12
574
(9) lbl
478
383
(9.0)
378
(9.4)
388
(9.0)
525
-
'1
2.0
1.8
103.0
IO'k
10- I ) [d]
11
-
lo4 k
[ S ~
[S
'1
1.3
2.8
86.0
[a] At 25°C in CH2C12.[b] Determined by the Fischer method 171. [c]Only IOc
and 10c' could be separately isolated.
0 VCH Verlagsgesellschafr mbH. 0-6940 Weinheim. 1986
0570-0833/86/0606-0573$ 02.50/0
573
droindolizines) 10. The adducts 10 were purified by column chromatography and recrystallized from ether. The
assignment of the structures of 10 was possible on the basis of the 'H-NMR, IR, and UV data.
The 'H-NMR spectra of 10a, b showed a sixfold splitting of the characteristic methyl ester signals and a complex splitting of the dihydropyridine and dihydropyridazine protons, respectively, thus indicating that both substances consist of inseparable diastereomers. 1Oc and 1Oc'
(dihydropyridazine rings either syn or anti to the planar
trans-fluoreneacene skeleton) could be isolated from the
reaction mixture formed upon reaction of 8c with pyridazine. According to the 'H-NMR spectrum the isomers 1Oc
and 1Oc' can interconvert by photochemical 1,5-electrocyclic ring opening and subsequent thermal cyclization.
The maxima in the UV/VIS region of 10a-c lie between
378 and 396 nm (Table 3) and d o not differ very greatly
from those of the analogous monofunctional systems
12[2",b1
(Table 3). The extinction coefficients of the bisadducts 10a-c are about a factor of 1.5 to 1.7 greater than
those of the monomers 12. In solution, the compounds
10a, c could be converted into the colored forms 9a-c by
irradiation with polychromatic light. A comparison of the
bis(betaines) 9 with the analogous monobetaines 11 likewise shows good agreement of the maxima. The &-values of
9a and l l a were determined from the degree of conversion using the Fischer rnethod"l (Table 3). Since the bisadduct 9a has an €-value 1.4 times higher for the longestwavelength absorption than the monomer l l a , it is very
likely that both rings of the bisadduct can be opened. This
photochemical ring opening 10 .-, 9'-9 should proceed in
two one-photon steps (cf. also f81). The rate constants of the
cyclization of the betaines 9-10 points in all cases to a
1st order reaction; actually more complicated kinetics had
been expected. The rate constants of the reaction 9-10
were increased in comparison to those of the monofunctional systems. The spiro bridge in 9c causes a drastic increase in the rate constant compared to that of the mobile
unbridged species 9a and 9b. The AH' values for the
cyclization of 9 lie between 14 and 19 kcal/mol, the A S f
values between -25 and - 6 cal mol-' K-'. Hence, the
AGg8 values for all the compounds 9 are ca. 20 kcal/mol.
That is, the novel bis(dihydroindo1izines) 10 exhibit photochromic properties that are due to a 1,s-electrocyclic reversion to the betaines 9.
Received: January 10, 1986;
revised: March 14, 1986 [Z 1617/1618 IE]
German version: Angew. Chem. 98 (1986) 565
141 a) A. Me'uwsen, R. Gosl, Chem. Ber. 92 (1959) 2521; b ) Y . Tamura, J.
Minamikawa, M. Ikeda, Synfhesis 1977, I: c) Y . Tarnura, J. Minamikawa, Y . Miki, S . Matsugashita, M. Ikeda, Tetruhedron Lett. 1972, 4133; d)
T. L. Gilchrist, C . W. Rees, J. Chem. SOC.C1968, 119.
15) 4a: 'H-NMR (CDCI,): 6=3.51 (s, 3 H, CHI), 4.62 ( m . 1 H, H-4). 5.21 (m,
1 H, H-6). 5.56 (rn, I H, H-3a), 5.79 (m,I H, H-5). 7.03 ( m , I H, H-7), 7.22
( m , 1 H, arom.), 7.3-7.45 ( m , 4 H , arom.), 7.50 (m, I H, arom.), 7.76 (m,
2 H, arorn.).
[61 a) R. W. Murray, A. M. Trozzolo, J. Org. Chem. 26 (1961) 3 109; b) J. van
Alphen, Red. Trau. Chim. Pays-Bas 62 (1943) 483; c) L. Schrader, Chem.
Ber. 104 (1971) 941.
I71 E. Fischer, J . Phys. Chem. 71 (1967) 3704.
[8] P. Spang, H. Diirr, Angew. Chem. 96 (1984) 227; Angew. Chem. I n f . Ed.
Engl. 23 (1984) 241
A Polyfunctional Dititanacyclobutane
By Hubert Schmidbaur,* Reinhard Pichl, and
Gerhard Miiller
Whereas the chemistry of the metal complexes of phosphorus ylides (type A ) has developed into a rapidly growing field of research['] with important app1ications,lz1 the
chemistry of metal-substituted ylides (type B) has been relatively little investigated. All the examples that have been
studied in detail are derived from the electron-deficient pand d-block elements.131
0 0
r13P-CH,
+
I:
M -
B
Apparently, absolutely no compounds of type B containing electron-rich metal centers (such as the late transition-metal elements in low oxidation states) have been accessible. All attempts led only to isomeric products."]
Moreover, even for the early transition metals, prototropism accompanied by the formation of a second metalcarbon bond between an R group of R3P and the metal
center is possible.
Thus, for example, an equilibrium mixture la/b is found
for the zirconium complex 1 (R=N(C,H,),) in solution.
Only when no acidic H atom is present in the a-position to
the P atom (e.g., in 2) does the complex exist exclusively as
an ~1ide.I~'
CAS Registry numbers:
la, 25275-41-6; lb, 57156-85-1; lc, 102149-96-2; Id, 102149-97-3; le,
102149-98.4: 2, 18083-75-5; 38, 102149-99-5; 3b, 102150-00-5; 3c, 10215001-6; 3d, 102150-02-7; 3, 102150-03-8; 4a, 102210-48-0; 4b, 102210-49-1:
4c, 102210-50-4; 4d, 102210-51-5: 4e, 102210-52-6; 6a, 102150-04-9; 6b,
102150-05-0; 78, 102210-53-7; 7b, 102150-06-1; 88, 102150-07-2; 8b, 10221054-8; 98, 102210-55-9; 9b. 102150-08-3; 9c, 102150-09-4; IOa, 102210-56-0;
lob, 102210-57-1: lOc, 102233-40-9: 118, 102150-10-7; l l b , 102150-1-8; l l c ,
72206-53-2; 12a, 102210-58-2; 12b, 102210-59-3: 12c, 72206-64-5; EC=CE,
762-42-5; Isoquinoline, 119-65-3; Phthalazine, 253-52-1; Pyridazine, 289-80-5.
lb
\
\
%
CH 2 - 0PR2
CH=PR,CH,
2
a ) N. Y . C . Chu, Proc. X-fh Symp. Phorochem.. Interlaken 1984; b) R. C.
Bertelson in H. G. Brown (Ed.): Photochromism. Wiley-lnterscience,
New York 1971; c) R. Dessauer, J. P. Paris, Adu. Phorochem. I (1963)
275; d) H. Sixl, Umschuu 8 3 (1983) 474.
(21 a) G . Hauck, H. Durr, Angew. Chem. 91 (1979) 1010; Angew. Chem. Inr.
Ed. Engl. 18 (1979) 945; b) H. Gross, H. Diirr, Angew. Chem. 94 (1982)
204: Angew. Chem. lnt. Ed. Engl. 21 (1982) 216; Angew. Chem. Suppl.
1982, 559.
[3] a) C . R. Hardy, Adu. Heferocycl. Chem. 36 (1984) 343; b) R. Huisgen,
Angew. Chem. 92 (1980) 979; Angew. Chem. Int. Ed. Engl. 19 (1980) 947.
Heterodtoms in 2,3-position of the hetero-pentadienyl anion.
[I]
574
0 VCH Verlagsgesellschafi mbH. 0-6940 Weinheim. 1986
By the introduction of bulky diethylamino groups on the
P atom, it has now been possible to replace both H atoms
['I Prof. Dr. H. Schmidbaur, Dipl.-Chem. R. Pichl, Dr. G. Miiller
Anorganisch-chemisches Institut der Technischen Universitat Miinchen
Lichtenbergstrasse 4, D-8046 Garching (FRG)
0570-0833/86/0606-0574 $ 02.50/0
Angew. Chem. Inl. Ed. Engl. 25 (1986) No. 6
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