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Arylcyanophenols and 2 4 6-Tricyanophenol.

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Table I . Substituents and melting points of compounds ( l l k ( 9 )
Table 1. Properties of compounds ( 3 a l - ( 3 d ) , ( 4 a ) . a n d ( 4 b ) .
Compound
H
H
OCH3
OCH,
H
CH3
Received, March 23rd, 1964
[ Z 703/535 IE]
German version: Ansew. Chem. 76, 440 (1964)
[ I ] Communication No. 17 on Hydroxylamine Derivatives.
Communication No. 16: G . Zinner and W. Ritter, Arch. Pharmaz. 296, 681 (1963).
[2] Cf. also 0.Piloty and H. Steinhock, Ber. dtsch. chem. Ges.
35, 3101 (1902).
[3] R. Scholl, Ber. dtsch. chem. Ges. 23, 3490 (1890), gives: b.p.
106.5-107.5 "C/14 mm and b.p. 223 "C/726 mm.
225-230
214-220
208-220
215-123
126 (decomp.)
178-185
472
472
485
485
592
587
4.37
4.37
4.34
4.34
4.27
4.11
Oxidation of (3a) - (Sd), (4u), and (46) by alkaline hydrogen
peroxide affords 2-benzothiazolones or 2-quinolones, together
with phosphoric acid, in quantitative yields.
The NMR-spectra are compatible with the cyanine structure;
the chemical shift of the phosphorus resonance (-26.05
pprn), however, is unexpectedly large and without parallel [*I.
The excellent agreement of the electron spectra with those of
the analogous aza- and rnethinecyanines supports the constitution proposed.
Received, March 24th, 1964
[ Z 706/528 IE]
Publication deferred until now at the authors' request
German version: Angew. Chem. 76, 433 (1964)
[*I We wish to thank Dr. E. Fluck, Heidelberg, for determining
the phosphorus N M R spectra, and for their interpretation.
Phosphacyanines, a New Class of Compounds
Containing Trivalent Phosphorus
By Prof. Dr. K. Dimroth and Dr. P. Hoffmann
Chemisches lnstitut
der UniversitLt MarburgILahn (Germany)
Arylcyanophenols and 2,4,6-Tricyanophenol
By Prof. Dr. K. Dimroth and Dr. K. J . Kraft
Chemisches Institut
der UniversitLt Marburg/Lahn (Germany)
Dedicated to Professor H . Meerwein
on the occasion of his 85th birthday
A solution 0.02 mole of N-ethyl-2-chlorobenzothiazolium
fluoroborate ( I ) , RI = CzHs, R 2 = H, and 0.01 mole of tris(hydroxymethy1)phosphine (2) in 10 ml of N,N-dimethylformamide (DMF) was treated at 0 "C under nitrogen with
0.03 mole of diisopropylethylamine dissolved in 10 ml of
D M F a n d yielded orange-red crystals of ( 3 6 ) ,with elimination
of formaldehyde.
We obtained analogous compounds from variously substituted 2-chlorobenzothiazolium salts and 2-chloroquinolinium salts; it appears therefore that phosphacyanines ( 3 )
R2
R2
or ( 4 ) ( i . e . analogues of the azacyanines) have been formed
(yields: 40-50 7:). Some of their properties are listed in
Table 1 .
384
Dedicated to Professor H . Meerwein
ott the occasion of his 85th birtliduj
The observation that 4-cyano-2,6-diphenylphenol( I ) can be
dehydrogenated to a stable, green phenoxyl radical [ I ]
prompted us to prepare further arylcyanophenols. 2-Cyano4,6-diphenylphenol (2) was obtained from 2,4-diphenylanisole by bromination, conversion into the corresponding
organolithium compound, carboxylation, preparation of the
amide, dehydration, and demethylation with pyridine/HCl
[2]. Compound (2) can be dehydrogenated to a red, stable
phenoxyl radical.
2,6-Dicyano-4-phenylphenol (3) was prepared from 4hydroxydiphenyl by condensation with formaldehyde to give
2,6-bishydroxymethyl-4-phenylphenol,methylation, oxidation to the dicarboxylic acid, conversion into the diarnide,
dehydration, and demethylation. Phenol ( 3 ) is oxidized with
lead tetraacetate in glacial acetic acid to give a blue radical
which has not yet been closely investigated.
Finally, we have prepared 2,4,64ricyanophenol ( 4 ) by conversion of methoxytrimesic acid into the triamide, dehydration, and demethylation. Like picric acid, (4) is a strong acid
(pKc = 1.0 at 20°C and ionic strength p - 0.02); it has not
yet been oxidized.
bH
OH
C:d35
CN
OH
6H
The half-wave potentials were measured polarographically i n
acetonitrile/water (9: I ) containing 0.01 M N(CH3)40H and
N(CH3)dCI with a rotating graphite electrode and a silver!
Angew. Cheni. ititernat. Edit. J Vol. 3 (1964) / No. 5
silver chloride reference electrode [3]. T h e potentials increase
considerably with increasing cyanation (Table 1).
phenol. Oxidation of this gave the dimer containing cu.
55 atom-"<; of 1 8 0 . The displacement of the infrared absorption bands (Table 1 ) demonstrates conclusively that the
Table I . Half-wave potentials
Compound
M.p. [ T I
Color of
radical
2,4,6-TriphenyIphenol [4]
4-Cyano2,6-diphenylphenol
2-Cyano4,6-diphenylphenol
2.6-Dicyano4-phenylphenol
2,4,6-Tricyanophenol
149-150
red
165-166.5
green
138- I39
red
215 (decomp.)
185 (decomp.)
blue
if,
R
5
I01
Received, March 24th, 1964 IZ 707/532 IE]
Publication deferred until n o w at the authors' request
German version: Angew. Chem. 76, 433 (1964)
[ I ] D . Schminke, Ph. D. Thesis, Universitat Marburg, 1961.
[2] The preliminary stages were investigated by K . Schromm,
Marburg.
[3] F. W. Steuher, Ph. D. Thesis, Universitat Marburg, 1963; F.
W. Steuber and K . Dimroth, Tagung fur moderne elektrochemische Analysenmethoden, Eisenach, April 1964.
[4] K . Dimrofh, F. Kalk, R. Self, and K. SchlBmer, Liebigs Ann.
Chem. 624, 51 (1959).
[ 5 ] F. Bcr, Marburg.
The Constitution of the Dimer of
2,4,6-Triphenylphenoxyl
By Prof. Dr. K. Dimroth a n d Dipl.-Chem. A. Berndt
R
I1
,
R
101
Table I. Characteristic absorption bands of dimeric [IbOl- and [l*O]2,4,6-triphenylphenoxyl ( 1 ) (approximately 5 5 atom- % ' 8 0 ) in CCI:.
1665
1642
1201
958 '
1665
1642
I620
I597
1185
956
45
45
16
7
T h e quinol structure ( I ) is thus demonstrated. T h e o-quinol
structure is not disproved by the above experiments, but
seems less likely. Scission of the C - - - 0bond of ( 1 ) in solution
t o form the radical, i.e. dissociation of the dimer ( I ) , requires
only a very small energy of activation.
T h e present results are confirmed by a n X-ray analysis of
dimeric 3-bromo-2,4,6-triphenylphenoxyl;
this work shows
in addition that the product in question is a p-quinol derivative [ 6 ] .
Received, March 24th, 1964
[Z 708/5?9 1El
Publication deferred until now at the authors' request
German version: Angew. Chern. 76, 434 (1964)
Dedicated to Professor H . Meerwein
on the occnsiorz of his 85th birthday
~
2,4,6-TriphenylphenoI is readily dehydrogenated t o a red
free radical, which is perfectly stable towards oxygen [ I ] a n d
which crystallizes as a colorless dimer. I n solution, the dimer
dissociates partly into 2,4,6-triphenylphenoxyl radicals (dissociation constant i n benzene: 4x 10-5 a t 20"C, heat of dissociation: ca. 10 kcal/mole). Equilibrium between the colorless dimer a n d red monomer is reached so quickly that
solutions of the former may be readily a n d without retardation redox-titrated, e . g . by using a solution of hydroquinone.
Introduction of large substituents (bromine or one or two
phenyl groups) into the central nucleus of triphenylphenol
displaces the position of equilibrium considerably in favor
of the dimerand reduces the speedwithwhich this equilibrium
is attained. These observations cast some doubt o n the
validity of formula ( I ) for the dimer. Although the infrared
spectrum of the dimer has a doublet at 1665 and 1642 cm-1,
which may be ascribed t o t h e C=O vibrations of a quinol [2],
the result would also agree with the presence of a diquinol
(2). A band a t 958 cm-1, i . e . in the region of -0-0- absorption, suggests a diphenyl peroxide structure ( 3 ) [3].
Formulation of the dimer as a n ion pair [4]is incorrect, since
neither the anion nor the cation [ 5 ] absorb in the region of the
doublet.
By reaction of 2,4,6-triphenylbenzenediazoniumfluoroborate
with CH3'8OH [*] and cleavage of t h e resulting methyl ether
with pyridinium chloride, we obtained [180]-2,4,6-triphenyIVoI. 3 (1964)
I
doublet at 1665 and 1642 cm-1 originates from a C - 0 L i b r a tion. T h e peroxide structure (3) is thus eliminated, all the
more so a s the band at 958 cm-1 is not significantly displaced.
T h e occurrence of a shift in the ether region excludes structure (2).
Chemisches Institut
der Universitat Marburg/Lahn (Germany)
/
I
R
-
These results show that for stabilization phenoxyl radicals
need not necessarily have bulky substituents a t the 2-, 4-, a n d
6-positions. All the radicals were characterized by ESR
measurements [5].
Arigew. Chem. iriternat. Edit.
R8R
/ No. 5
~-
[ I ] K . Dimroth, F. Kalk, R . Sell, and K . Schlomer, Liebigs A n n .
Chem. 624, 5 1 f 1959).
[ 2 ] E. Miiller, K. Le,v, and G. Scltlechte, Chern. Ber. 90, 2660
(1957).
[3] S t . Goldschmidt and Ch. Steigerwold, Liebigs Ann. Chern.
438, 202 ( 1 924).
[4] E. Miillcr, K. Ley, and W . Schntidhuber, Chem. Ber. 89, 1738
( 1 9 5 6).
[ 5 ] W. Umbnch, Ph. D. Thesis, Universitat Marburg, 1962.
[6] R . .4/lmonfi, personal communication.
["I We wish to thank Prof. D. Sasluel, Rehovoth, Israel, for t h c
labelled methanol.
Complexes of Organotin Compounds with
Aluminum Halides
By Priv.-Doz. Dr. W. P. Neumann,
Dipl.-Chem. R. Schick [ I ] , a n d Dr. R . Koster
Chemisches lnstitut der Universitlt GieBen and
Max-Planck-Institut fur Kohlenforschung,
Miilheim/Ruhr (Germany)
In carrying o u t alkylations o n tin, Kvstrr [2] obtained in 1955
the crystalline complexes ( 3 ) and (7). U p t o then, only
compounds of organotin halides with Lewis bases were
known [3]. In preparing starting materials such as tin tetraalkyls, we came again across these complexes [4,5].
385
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