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Azobenzene Phanes.

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Table I . Synthesis of esters 2-7 [a, b] by addition o f the crotyltitanium compound 4 to aldehydes 6 .
[%I [cl
Id, el
'H-NMR of Z-714
J, 4
2-7 : Z-8
: <0.5
: 2.4
: 2.5
[a] Satisfactory CH analyses obtained. [b] Racemic mixtures. [c] Crude product homogeneous according to 'H-NMR and thin layer chromatography. [d]
Determined by capillary gas chromatography [I]. [el Poorest value from two
or three experiments. When freshly prepared 5 was used, the fraction of 2-8
decreased to approx. half these amounts. [q In CCI,.
less than 1% (detected by gas chromatography[''). A high
regioselectivity of the carbonyl addition is also observed
with 1-alkylated derivatives; thus, 10 and 2,2-dimethylpropanal 6a react to form the y-adduct 11 free of isomers
(yield 87%). Methanolysis of the enol ester 2-7 (methanol,
1 equiv. methanesulfonic acid, 1 mol% Hg(1i) acetate,
25"C)['] affords the lactol ether 12. Dimethyl acetals 14
were obtained analogously via acetates 13"l. 12 and 14
Azobenzene Phanes**
By Dieter GraL Helmut Nitsch, Dieter Ufermann.
Gisela Sawitzki, Helmut Patzelt, and Hermann Rau*
We have synthesized 2,19-dithia[3.3](4,4')-truns-diphenyldiazeno(2)phane 1 and 2,19,36,39-tetrathia[](3,3',5,5')-tran~-diphenyldiazen0(4)phane 2, the first azobenzene phanes, in order to study the interactions of the
azobenzene electron systems and to investigate the transcis isomerization. 1 and 2 are potential precursors of molecules containing the tetraazacyclobutane moiety.
Cyclization of 4,4'-bis(bromomethyl)azobenzene with
Na2S (high
afforded 1 as a yellow powder in
40% yield (crude yield 80%)[2a1.Likewise['', alkaline condensation of 3,3',5,5'-tetrakis(mercaptomethyl)azobenzene
with 3,3',5,5'-tetrakis(bromomethyI)azobenzene under high
dilution conditions furnished 2 (crude yield 60?/0)[~~].
structure analysis[31indicated that 1 has point symmetry
and parallel trans-azo groups; the benzene rings are inclined cu. 20" relative to one another. Bond-lengths and
-angles are similar to those of azobenzene. The separation
of the azo groups is 386 pm and that of the center of gravity of the benzene rings 357 pm (only slightly more than
the "thickness" of the aromatic n-~ystem'~]).
are versatile, useful derivatives of homoaldol 9. Hence, a
method is thus available for the homoaldol reaction (to our
knowledge the only['') which is just as efficient as the best
variants of the aldol reaction.
Received: March 19, 1982 [Z 88b IE]
German version: Angew. Chem. 94 (1982) 378
[I] D. Hoppe, F. Lichtenberg, Angew. Chem. 94 (1982) 378; Angew. Chem.
Int. Ed. Engl. 21 (1982) 372; and literature cited therein as well as stereochemical correlations and terminology.
121 D. Hoppe, R. Hanko, A. Bronneke, F. Lichtenberg, Angew. Chem. 93
(1981) 1106; Angew. Chem. Int. Ed. Engl. 20 (1981) 1024.
[3] lnstead of the bromide [4el we used the readily accessible chloride 5 prepared from lithium diethylamide and titanium tetrachloride (3 : I )
(b.p. = I15"C/0.005 torr); c/: also F. Benzing, W. Kornicker, Chem. Ber.
94 (1961) 2263.
[4] Synthetic applications of allyltitanium reagents: a) F. Sato, S. Iijima, M.
Sato, Tetrahedron Let?. 22 (1981) 243; b) M. T. Reetz, R. Steinbach, J.
Westermann, R. Peter, Angew. Chem. 92 (1980) 1044; Angew. Chem. Int.
Ed. Engl. 19 (1980) 1011; c) B. Weidmann, L. Widler, A. G. Olivero, C.
D. Maycock, D. Seebach, Helu. Chim. Aeta 64 (1981) 357; d) F. Sato, K.
lida, S. Iijima, H. Moriya, M. Sato, J . Chem. Soe. Chem. Commun. 1981,
1140; e) M. T.Reetz, R. Steinbach, J. Westermann, R. Urz, B. Wenderoth,
R. Peter, Angew. Chem. 94 (1982) 133: Angew. Chem. I n f . Ed. Engl. 21
(1982) 135: f) B. Klei, J. H. Teuben, H. J. de Liefde Meijer, J . Chem. SOC.
Chem. Commun. 1981, 342.
[S] Generalprocedure. 2-7:1.1 equiv. of 5 as a ca. 1 M solution in hexane is
added to a ca. 0.3M solution of 2 121 in ether/hexane under
-78'C. the mixture stirred for 1 h at -78°C. and 1.0-1.1 equiv. of 6
then added. After 30 min at this temperature, the cold reaction mixture is
poured into 10 mL (per mmol 2) of 2 N hydrochloric acidlether (1 : 1 v/
v), the aqueous layer extracted with ether, the ether removed, and the
combined extracts washed with NaHC03 and KCI solutions. After drying
(MgSO,) and removal of the solvent in uacuo, almost pure 2-17is obtained
(Table I).
Angew. Chem. Int. Ed. Engl. 21 (1982) No. 5
Fig. 1. Absorption spectrum of 1 (-), c = 1.6 x
(-), c not determined, in toluene.
I Inml-
mol/L in benzene and 2
In contrast to 4,4'-dimethylazobenzene 3, the UV n+n*
bands of 1 and 2 (Fig. 1) are split: increasing hypsochromic shift of the intense short wavelength component
band (0-0 transition in 3 : 360 nm; 1 : 344 nm; 2 : 339 nm)
and bathochromic shift of the typically weak phane band
(1 : ca. 380 nm; 2: ca. 395 nm) are observed. The vibrational structure of the short wavelength component band is
Prof. Dr. H. Rau, Dr. D. Grgf, Dr. H. Nitsch, Dr. G. Sawitzki, Dr. H.
Patzelt, D. Ufermann
FG Physikalische Chemie, Institut fur Chemie der Universitat Hohenheim
Garbenstrasse 30, D-7000 Stuttgart 70 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
0 Verlag Chemie GmbH. 6940 Weinheim. 1982
0570-0833;82;0505-0373 S 02.50;O
characteristic of phanes (used as a criterion in the isolation
procedure) and can be interpreted as arising from the increased rigidity of the molecular framework relative to that
of simple azobenzenes. The long wavelength n+n* bands
at 450 nm become weaker with increasing planarity of the
interactions beazobenzene units in the series 3-1-2;
tween the n orbital systems cannot be established with certainty.
1 and 2 isomerize under the action of lightI5'. This is experimental proof that rrans-cis-photoisomerization of azobenzenes can occur by inversion of the bond angle at nitrogen.
By means of kinetic analysis of irradiation experiments
in highly dilute solutions we have obtained evidence for
the possible formation of tetraazacyclobutane: Apart from
the trans-cis isomerizations an additional reaction, which is
not very important compared to the isomerizations, is observed that leads to a molecule forming the phanes quantitatively, unless A,,, < 320 nm whereupon the azo groups
are destroyed (azobenzene and bis-@-benzeneazotoly1)sulfide are stable under these conditions). At present we are
investigating the irradiation of powders (analysis by photoacoustic spectroscopy) and of crystals (X-ray structure
ana! ysis).
We describe here several novel macromolecular isocyanides of type 2 and 5 (see Table 1).
These polymers afford the combination of the versatile
reactivity of the isocyanide group['"' with the advantages
of solid-phase techniques. In contrast to isocyanomethylpolystyrene, our new isocyanide resins have excellent solvent compatibility. The new resins have a swellability of
5-10 mL/g in a wide range of solvents, including water,
methanol, dimethylformamide, dichloromethane, benzene,
and pyridine.
C 0-A-N
Received: June 18, 1980 12 91 IE]
revised: March 23, 1982
German version: Angew. Chem. 94 (1982) 385
[I] V. Boekelheide, R. A. Hollins, J. Am. Chem. SOC. 95 (1973) 3201; F.
Vagtle, U.Wolz, Chem. Exp. Didakt. I (1975) IS.
121 a) 1: Chromatography on Sephadex LH 20 and S O l (40"C, dimethylformamide and benzene, respectively), and crystallization by slow (8 weeks)
evaporation of toluene as solvent; above 230°C red, above 275°C dark
rnol/L in n-hexane
red, does not melt up to 310°C: solubility; ca.
and EtOH, ca. 2 x lo-' mol/L in toluene, readily soluble in acids; 'HNMR (CDCI?): 6=7.43, 7.33, 7.13, 7.03 (4. aromat. H), 3.89 (s, CH2);
MS: m / z 480, 194, 210, 120, 227, 254, 181, 240, 526, 135: FD-MS m/r:
480; b) 2 : Chromatography on SiOz with CHICl2; change of color above
250"C, decomp. ca. 290°C: insoluble in n-hexane and EtOH, sufficient
amounts for spectroscopy in supersaturated solutions of toluene, CH2CIz,
and CHCI>, dry samples insoluble; readily soluble in H2S04 and
CF,COOH with slow decomposition; 'H-NMR (CDCI,, supersaturated):
6=7.31, 7.22 (d, aromat. H ( 2 : I)), 3.98 (s, br. CHI) MS: m / z 596, no fragmentation; high resolution [Zc]: m / z 596.1 196 (calc.), 596.1 195 (found); c)
we thank Dr. Rodzinski, Universitat Stuttgart for recording this spectrum.
131 G. Sawitzki, H. Rau, Liebigs Ann. Chem. 1981. 993.
[4] For example L. Pauling: The Nature o f t h e Chemical Bond, Cornell University Press, lthaca 1948, p. 172: L. S. Lermann, Proc. Nat/. Acad. Sci.
USA 49 ( 1963) 94.
IS] E. Luddecke, H. Rau, J . A m . Chem. Soc.. in press.
Synthesis of Macromolecular Isocyanides with
General Solvent CompatibilityNovel Polymer Supports for
Solid-Phase Syntheses**
By Reza Arshady* and Ivar Ugi
Polymer-supported reagents and solid-phase techniques
have assumed an important role in many areas of chemistry, e.g. in the synthesis of peptides and oligonucleotides,
as well as in catalysis by enzymes and transition-metal
[*] Dr. R. Arshady [ '1, Prof. Dr. 1. Ugi
Organisch-Chemisches lnstitut der Technischen Universitst Munchen
Lichtenbergstrasse 4, D-8046 Garching (Germany)
[ J Present address:
Department of Chemistry
Imperial College, London SW7 2AZ (England)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
0 Verlag Chemie
GmbH. 6940 Weinheim, 1982
Table I . Examples of resins of type 2 and 5 .
la, bl
I .o
3.3 [b]
[a] The data are based on the initial polymer compositions; all of the polymers were subjected to quantitative analysis and showed isocyanide contents
of loo+ 10% of the theoretical values. [b] The isocyanide content of some of
the polymers stored at room temperature was found (by IR spectroscopy
v(NC)=2150 cm-I) to gradually decrease, most rapidly for Sb, whose isocyanide absorption disappeared completely within 2-3 months.
The macromolecular isocyanides 2 and 5 are obtained
by dehydration of the formamides 1 and 4, respectively.
Here, tosyl chloride in pyridine is the reagent of
The formamide bead polymers 1i'21are directly available via suspension polymerization, whereas the formamides 4 are derived from the copolymer 3[I3].The monomers
needed for 4 are not compatible as comonomers for suspension polymerizations.
Received: October 16, 1981 [Z 79 IE]
revised: March 10, 1982
German version: Angew. Chem. 94 (1982) 367
The complete version of this manuscript appears in:
Angew. Chem. Suppl. 1982, 761-768
[6] For a comprehensive review see P. Hodge, D. C. Sherrington: Polymersupported Reactions in Organic Synrhesis. Wiley, Chichester 1980.
171 a) R. Arshady, I. Ugi, Z . Naturforsch. B 36 (1981) 1202.
[ I I J I. Hagedorn, H. Tonjes. Pharmarie 11 (1956) 409; W. R. Heitler, E. J.
Corey, J. Org. Chem. 23 (1958) 122.
[I21 R. Arshady, Polymer, in press.
[I31 R. Arshady, Makromol. Chem. Rapid. Commun. 2(1981) 513.
0570-0833/82/0505-0374 S 02.50iO
Angew. Chem. Int. Ed. Engl. 21 (1982) No. 5
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phanes, azobenzene
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