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New Methods of Preparative Organic Chemistry IV.

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New Methods of Preparative Organic Chemistry IV
Syntheses with Nascent Quinones
lf’ catechot or other hydroquinones are dehydrogenated in the presence of a nucleophilic
reagertt, the latter reacts, usually by Michael addition, with the quinone formed in situ.
The wide range of possible variations oflered by this synthetic method is comprehensively
described in the present pauer. Procedures are given for carrying out typical reactions.
1. Introduction
ted from reacting %rther . . . . . . . the formation of a hydroxy
or amino sulfone indicates that the quinone was present in
the oxidation mixture, even if only for a short time.”
Demonstration Experiment : A solution of 3 g of sodium
p-toluenesulfinate in 50 ml of water and 10 ml of acetic
acid is poured into a solution of 1 g of p-benzoquinone
in 10 ml of acetic acid and 50 nil of water. The mixture
is decolorized within a few seconds and purely white 2,5dihydroxyphenyl p-tolyl sulfone ( 1 ) immediately sepa-
This analytical conception contains a s y n t h e t i c a l
p r i n c i p l e , an account of which is given below. The
syntheses in question have the following point in
common : dehydrogenation of catechol or another
quinone former in the presence of a nucleophilic reagent
yields a product which is (normally) formed by Michael
addition of the nucleophile onto the quinone produced
in situ.
2. Simple Examples
rates out. In 1896, on the basis of this addition, which
proceeds extremely readily, Hinsberg and Himmekchein
[l] carried out a simple experiment: they oxidized
catechol in the presence of benzenesulfinic acid and
a) Additions of Sulfinic Acids, Sulfite, and Thiourea
In the course of work on the mechanism of the formation
of purpurogallin, Horner et al. studied the dehydrogenation of pyrogallol in the presence of benzenesulfinic acid to form the sulfone ( 4 ) [3,4].
The sulfinic acid adds onto the 3-hydroxy-o-benzoquinone (3) formed in situ; (3) has never been isolated.
obtained the sulfone (2). Their clear conception of this
experiment, which is given here in its modern formulation, is shown by their own words [l]:
“Benzenesulfinic acid combines with quinones and iminoquinones, and reacts rapidly at normal temperatures to yield
hydroxy or amino derivatives of sulfones [2]. If benzenesulfinic acid is present at the moment of formation of a
quinone (or iminoquinone) of low stability, the former is
converted into the corresponding sulfone, and is thus preven~~~
[*] The papers of the previous three series are collected in three
volumes published ir, English by Academic Press, New York,
[I] 0.Hinsberg and A . Himmelschein, Ber. dtsch. chem. Ges. 29,
Dehydrogenation of alizarin (5) in the presence of p toluenesulfinic acid leads via the o-quinone (6) to the
sulfone (7) [ 5 ] . Sulfite can also add onto (6) to form the
sulfonic acid (8).
[ 3 ] L. Horner and W. Diirckheirner. 2. Naturforsch. 14b, 143, 144
2023 (1896).
121 0. Hinsberg, Bcr. dtsch. chem. Ges. 27, 3259 (1894); 28, 13 I5
141 L. Horner and S . Gowecke, Chern. Ber. 94, 1267 (1961); L .
Horner, K . H . Weber, and W. Diirckheimer, ibid. 94,2881 (1961).
[5] H . Heidepriern, Ph. D. Thesis, Technische Universitgt Berlin,
Angew. C h e m . internat. E d i t . [ Vol. 3 (1964) 1 No. 6
40 1
nitrite used leads to 3,4-dinitrocatechol (13) as the
principal product 191. Nothing was previously known
of the mechanism of the reaction.
On the basis of the idea that the reaction might proceed
via o-benzoquinone as an intermediate, the nitrous acid
playing the double role of dehydrogenating agent and
nucleophilic reagent, we developed a new, simple
procedure in which catechol is dehydrogenated with
K3Fe(CN)6 in the presence of sodium nitrite [lo].
The addition in the 3-position is remarkable. It means
that polarization of the diquinone (6), which is so far
only known in solution [6], in the direction indicated
in (6a) predominates over the expected polarization
Preliminary experiments showed that repeated dehydrogenation of ( I I) in the presence of nitrite leads to (13)
[5]. The electron-attracting effects of the carbonyl and
nitro groups indicated in (12) must be jointly responsible
for the entry of the second nitro group [ l l ] at position 3.
The addition of thiourea onto nascent o-benzoquinone
proceeds satisfactorily [7] to yield S-(3,4-dihydroxypheny1)isothiourea (10).
Procedure :
A solution of 65 g of potassium hexacyanoferrate(Il1) and
100 g of crystalline sodium acetate in 230 ml of water is rapidly
added dropwise to a mechanically stirred solution of 13 g
of catechol and 7.6 g of thiourea in 100 ml of water. The
reaction product begins to separate out even during the
dropwise addition. Further 100 g of crystalline sodium
acetate are added, and the mixture is stirred for another
hour, filtered by suction, and washed with a little water. The
crude product is purified by dissolving it in dilute hydrochloric acid and stirring the clarified solution into a concentrated sodium acetate solution. The acetate of S-(3,4dihydroxypheny1)isothiourea (10) is obtained in over 90
yield. M. p. ca. I80 "C (decomp.).
b) Nitrite Addition
In 1878, Berzedikt [SJ discovered an unusual route to 4nitrocatechol (11) by treatment of pyrocatechol with
n i t r o u s acid. A more recent, improved procedure [9]
gives yields of up to 37 %. Increase in the quantity of
[6] 0. Dimrotli and E S r h d z e , Liebigs Ann. Chem. 411, 345
(I9 16).
[7] H.-W. Wanzlick, Angew,. Chem. 72, 581 (1960).
[8] R . Benedikt, Ber. dtsch. chem. Ges. 11, 362 (1878).
[9] D . H . Rosenblatt, J . Epstein, and M . Levitch, J. Amer. chem.
SOC.75, 3277 (1953).
A solution of 20 g of potassium heh.acyanoferrate(ll1) and
17 g of crystalline sodium acetate in 100 ml of water is added
to a solution of 3.3 g of catechol, 2.1 g of sodium nitrite,
and 2.2 g of crystalline sodium acetate in 50 in1 of water. The
resulting dark red mixture is filtered after 5 minutes and
extracted with 200 ml of ether in several portions. The extract
is dried with sodium sulfate, the ether is distilled off, and the
brownish residue is pressed out on porous tile to yield about
2 g (43 %) of practically pure 4-nitrocatechol (11). This may
be completely purified by recrystallization from water or by
sublimation in vocuo. M.p. 174 "C.
Dehydrogenation of alizarin ( 5 ) in the presence of
nitrite yields alizarin orange (9) [ 5 ] .
c) Amine Addition
Since the groups introduced into the phenols in Sections
2a) and 2b) i n c r e a s e their oxidation potentials [12], it
is easy to find conditions under which the reaction can
be stopped after completion of the first dehydrogenation-addition process. On the other hand, if substituents which d e c r e a s e the oxidation potential [12]
are introduced, then secondary reactions become
inavoidable. The formation of 4,5-dianilino-o-benzo~
[lo] R. G r i t z k y , Diploma Thesis, Technische Universitit Berlin,
[ I I ] Compare this with the formation of 2,3-dicyanohydroquinone [J. Thiele and J. ibfeisenheimer, Ber. dtsch. chem. Ges.
33, 675 (1900)]. The participation of the carbonyl group at C-9
in promoting the polarization in (6a) should also be taken into
consideration in the additions of alizarinquinone ( 6 ) .
[12] L . F. Fieser and M . Fieser: Organic Chemistry. 2nd Edit.,
Heath, Boston 1950, p. 755.
Airgew. Cliern. iiiieriiut. Edit. 1 Vol. 3 (1964) No. 6
quinone (15) during the dehydrogenation of catechol
in the presence of aniline has long been known [13]. The
widely adaptable synthesis which involves the series of
steps D-A-D-A-D
[I41 is the subject of recent
patents [15]. Horncr and Lung [I61 added secondary
arnines onto o-quinones produced in sitii and obtained
inter alia the aminoquinones (14), (16), and (17).
d) Additions of Water and Alcohols
Only one example can be given here €or the addition of
w a t e r and a l c o h o l s onto nascent quinones. Horner
and Giiwecke dehydrogenated catechol in rnethanolic
mineral acid solution and obtained products, c.g. (22)
from 3-methoxycatechol, which are formed by way of
herniketals [20].
I ? ? ) , 71"<>
OCIl j
N-Methylaniline adds on only once. The steps in the
formation of (14) are therefore D-A-D [14].
If isolated o-quinones are used as such in this reaction,
niethoxylation only occurs in particular cases and in
considerably poorer yields.
3. Bifunctional Addends
Catechol (0.55 g) is dissolved in 100 m i of acetone, a n d 7 g of
silver oxide a n d 10 g of calcined sodium sulfate ar e added.
T h e solution is cooled to 0 " C ,treated with 2 ml of dimethylamine from a well-cooled pipet, a n d shaken. Processing
after 10 minutes gives (16), m.p. 149 O C (decomp.), in 53
Cu(1I)-catalysed autoxidation of hydroquinone in the
presence of dirnethylamine leads quantitatively to ( 1 8)
The initial product of the reaction of an amine with obenzoquinone is the monoaminoquinone of type (14).
If the aniine contains another nucleophilic group in a
favorable position, intraniolecular secondary reactions
take place.
In work on insect pigments, Butenandt et al. [2 I , 221 were
able to show that dehydrogenation of catechol in the
presence of the o-aminophenol (23) yields 5-acetyl-3hydroxy-2-phenoxazone (24) [23].
I n t r a m o l e c u l a r arnine additions are also possible
and have been known for some time. The formation of
adrenochrome (21) has been studied particularly
thoroughly and might also be mentioned and forniulated
at this point [18].
A suspension of 200 nig of 2-amino-3-hydroxyacetophenone
hydrochloride, 200 nig of catechol, a n d 2.1 g of powdered
potassium hexacyanoferrate(II1) is prepared in 5 ml of
Dehydrogenation of epinephrine (19) initially gives rise
to (20), which can be detected for a short time [19].
Subsequent A-D steps [I41 lead to the formation of
adrenochrome (21).
[I31 F. Kelirinanii and M . Cordune, Ber. dtsch. chem. Ges. 46,
3009 (1913).
[I41 D = Dehydrogenation, A = Addition.
(151 J . R . Geigy AG.. see Chem. Zbl. 1960, 6926; 1Y62, 9520.
[I61 L . Horner and H Lnng, Chem. Ber. 89, 2768 (1956).
[I71 A. N . Grinev, I . A. Saitzev, N . K. Venevzeva, and A . P . Terentyev, Zh. obshchei Khim. 30, (Y2), 1914 (1960); Chem. Zbl.
1961, 13 166; cf. R . 5aItrl.v and E. Lorz, J. Amer. chem. SOC.70,
861 (1948); A . H . Crosby and R . E. Lutz, ibid. 76, 1233 (1956).
[IS] Review: R . A . Heacock, Chem. Reviews 59, 181 (1959); see
also R . A. Hencock, 0 . Hutzinger, B. D . Scott, J . W. Dcly, and
5. Witkop, J . Amer. chem. SOC. 85, 1825 (1963).
Airgew. Clienl. iirtrrimt. Edit.
Vol. 3 (1964)
No. 6
acetic acid dried over copper sulfate, ar.d t h e mixture is
shaken in a n atmosphere of car b o n dioxide at room temperature. Separation of t h e product starts right a t the
beginning of t h e reaction a n d is brought t o completion by
controlled addition of water. C o mp o u n d (24) is obtained in
4 3 9/, yield, m.p. > 400 OC.
A fundamentally similar combination takes place when
o-arninophenols are dehydrogenated a I o ne; the products are 3-amino-2-phenoxazones. Important syntheses
of natural products may be quoted in this connection :
in particular those of Brocknianrz et a l . in the series of
[I91 A . Kodjrr and S. 5oucl1illuux,C . R. Seances SOC. Biol. Filialcs
153, 1407 (1959); Chem. Zbl. lY60, 15436.
[20] For details of the mechanism, see L . Horwer and S. Gdwecke,
Chem. Ber. 94, 1291 (1961).
[21] A. Buretiandt, Angew. Chem. 6Y, 16 (1957).
1221 A . Bufenandr, Verhandl. Ges. dtsch. Naturforscher, Arzte
1959, 152.
I231 A. Butenandt, E. Biekert, and G . Neubert, Liebigs Ann. Chem.
602,12 (1957).
actinomycins [24,25] and those of Butenandt et al. in
the field of ommochromes [21,22]. The dehydrogenation
of 2- amino - 3 - hydroxyacetophenone (23) proceeds
smoothly to yield 3-amino-4,5-diacetyl-2-phenoxazone
(25) [26]. 3-Hydroxykynurenine (26) yields (27), which
can be converted into the ommochrome xanthommatin
(23), R' = H
R2 = CO-CH3
(261, R1 = H
R2 = CO - CH2 - CH(hJ2)COOH
(28), R' = CH3
(301, 1%' = CH3
(32), R' = H
(25), 8 0 5
(311, >OO$
(33), 5 0 5
the direction of the primary addition to give preferentially (3s). Since, in the syntheses considered in the
present paper, the residue R2 contains a carbonyl group
attached directly to the ring, it is possible that the
primary addition formulated in (35) is further promoted
by polarization in the sense shown in (36) (cf. (12) and
4. C-C Bonding
In the course of their investigations on the formation
of melanins, Bu'Lock and Harley-Mason [32] dehydrogenated 4-methylcatechol in the presence of indole and
obtained (37).
Dehydrogenation of (28) yields (29), i. e. the chromophore of the actinomycins [28], and actinocylbis(g1ycine
methyl ester) (31) is obtained from (30) [28]. These
results finally led to the total synthesis of actinomycin
C3 by a similar method [24].
There is no doubt that these syntheses largely correspond to the course of the biosynthesis [28,28a], as is
also true of the biogenesis of cinnabaric acid (33) and
similar natural products [29]. The dehydrogenation of
(32), which results in the formation of (33), was carried
out even before the discovery of the natural product
[30]. One prerequisite for the smooth occurrence of
these phenoxazone syntheses is the "correct" combination of the aminophenol with the iminoquinone
formed from it in situ; compounds of type (34) do not
occur at all, or are only present-as by-products. .'
To our knowledge, this is the first case of intentional
formation of a C-C bond via a nascent quinone.
We found the conditions (D-A [14]) particularly simple
in the synthesis of brevifolin (40) [34], a tannin constituent discovered and identified by Schmidt and Bernauer [33]. Gallic ester is dehydrogenated in the presence of cyclopentane-l,2-dione-3,5-dicarboxylic
Michael addition of this CH-acidic compound onto the
o-quinone (38) which occurs as an intermediate (but
which has not yet been isolated) yields (39), which is
converted into (40) simply by treatment with acid.
The strongly nucleophilic character of the amino group
and the extreme proneness of the group C=C-C=N- to
undergo addition reactions (greater than that of the
system C=C-C=O [31]) must be assumed to determine
140), 1 3 %
[24] H. Brockmann and H. Lackner, Naturwissenschaften 47,230
(1960); 48, 555 (1961); cf. Angew. Chem. 72, 533, 939 (1960).
[25] H . Brockmann, Progr. Chem. org. nat. Prod. 18, 1 (1960).
[26] A . Butenandt, U.Schiedt, and E. Biekert, Liebigs Ann. Chern.
588, 106 (1964), where earlier literature on the dehydrogenation
of o-aminophenols is cited.
(271 A . Butenandt, U.Schiedt, E. Biekert, and R . .I.
T. Cromartie,
Liebigs Ann. Chem. 590, 75 (1954).
[2S] H. Brockmann and H. Muxfeidt, Chem. Ber. 91, 1242 (1958).
[28a] A . Butenandt and W . Schufer in [52].
1291 J. Gripenberg, Acta chern. scand. 12, 603 (1958).
[30] A. Butenandt, J . Keck, and G. Neubert, Liebigs Ann. Chem.
602, 61 (1957).
[31] Cf. C. Schroeder, S. Preis, and K . P . L'nk, Tetrahedron
Letters 1960, No. 13, 23, where further references are given.
If the coreactant contains an active methylene group,
the primary adduct is readily dehydrogenated further.
Pyrocatechol and isopropylidene malonate (Meldrum's
acid) (41) yield (42a, 6 ) ; it is the quinone-niethide form
(42b) that occurs in red crystals [lo]. The mesomeric
anion corresponding to the tautomers (42a, b) is intensely
[32] J. D . Bu'Lock and J . Harley-Mason, S. chern. SOC.{London)
1951, 703.
[33] 0.Th. Schmidt and K . Bernauer, Liebigs Ann. Chern. 588,211
(1954); K . Bernouer and 0 . T h . Schmidt, ibid. 591, 153 (1955).
1341 H.-W. Wanzlick, Chem. Ber. 92, 3006 (1959).
Angew. Chem. internat. Edit. 1 Vol. 3 (1964) 1 No. 6
blue, and aqueous solutions of the alkaline salts are
stable for some time.
cognized and which was synthetized by a classical
method by Gripenberg 1381, can be prepared without
appreciable difficulty.
+Catechol, - 4 11
+ Catechol, - 4
(426), 4 0 %
1461, 7 0 %
If (4I) is replaced by dimedone (43), the corresponding
product (44) cannot be isolated (but can be observed
for a short time in solution, see below). A subsequent
spontaneous intramolecular addition leads to the formation of the curnarone derivative (45) [35,36].
A solution of 3 g of potassium hexacyanoferrate(II1) in 30 ml
of water is added in t w o portions to a solution of 1 g of
catechol, 2 g of dimedone, and 12 g of sodium bicarbonate in
150 ml of water. The resulting blue color is visible for a few
seconds. The cumarone derivative (45), m.p. ca. 280°C
(decomp.), precipitates out immediately.
This new synthesis of 5,6-dihydroxycumarone derivatives of type (45) is very adaptable. Thus, wedelolactone
(46) [35], which was isolated and whose structure was
elucidated by Govindachari et al. [37], and thelephoric
acid (48) [5], the constitution of which was first re~~
The 2,s-dihydroxy-p-benzoquinone
(47) used in the
synthesis of thelephoric acid functions as a double 1,3dicarbonyl system in the sense indicated.
The strong tendency of pyridinium salts of type (49) to
undergo addition and condensation reactions is known
from the comprehensive investigations of Krohnke et al.
[39]. Additions onto quinones introduced as such gave
remarkable results [40]. It was therefore natural to
attempt similar syntheses with nascent quinones.
[35] H.- W . Wanzlick, R . Gritzky, and H . Heidepriem, Chem. Ber.
96, 305 (1963).
[361 B. Eisterf and F. Geiss [Tetrahedron 7, 1 (1959)], have shown
that Meldrum's acid ( 4 1 ) and dimedone (43) exhibit differences
in their tendencies towards enolization: only (43) enolizes. The
difference between the reactions mentioned above is therefore
[37] T . R . Govindachari, K. Nagardjan, B. R . Pui, and P . C. Parthasarathy, J. chem. SOC.(London) 1956, 629; 1957, 545, 548.
Angew. Chem. internat. Edit. 1 Vol. 3 (1964) No. 6
If catechol is dehydrogenated in the presence of (49),
the product is the dibenzoylethylene derivative (52).
The reason for this surprising result is as follows:
addition of (49) or (49a) onto o-quinone formed in situ
initially yields (50). This readily splits off pyridine and
so, as a potential quinone rnethide (SI), can add on
another molecule of (49a) as shown. Further elimination
of pyridine finally leads to (52).
(52), H = H , 4 2 %
(53), H = CH3, 5 0 %
A solution of 3.29 g of potassium hexacyanoferrate(II1) in
100 ml of water is added to a solution of 0.62 g of 4-methylcatechol, 2,78 g of phenacylpyridinium bromide, and 10 g of
1381 J . Gripenberg, Tetrahedron 10, 135 (1960).
1391 F. Krdhnke, Angew. Chem. 75, 181 (1963), where references
to earlier reviews are given; Angew. Chem. internat. Edit. 2, 225
( I 963).
[40] F. Krohnke and H . Schmei/3, Ber. dtsch. chem. Ges. 70, 1728
(1937); K . Pfleghar, Ph. D. Thesis, Universitat GieDen, 1962; cf.
F. Krohnke and W . Zecher, Angew. Chern. 74,811 (1962); Angew.
Chem. internat. Edit. I , 626 (1962).
[41] B. Pwzkow, Ph. D. Thesis, Technische Universitat Berlin,
crystalline sodium acetate in 200 nil of water a n d 100 ml of
acetone. After 12 hours, t h e reaction mixture is extracted
with ether a n d worked up in t h e usual manner. Yield:
of (53) , m . p . 175 ‘ C .
a b o u t 50
By altering the experimental conditions, it is possible
to isolate the salt (50), R = CH,, initially formed. Further reaction of this with (49) in acetate-buffered solution leads smoothly to (53), confirining the reaction
sequence formulated above. Compounds (52) and (53)
react readily with hydrazine to form pyridazines (54).
The fact that (50) can be isolated opens up a route to
further syntheses, which will be reported elsewhere [41].
Other reactions proceeding with the formation of a C-C
linkage will be discussed in the next Section. The dimerization of o-quinones [42] and the formation of
purpurogallin [3,4] (cf. also [43]) can only be referred to.
product results from the addition of the naphthol onto
the $-naphthoquinone initially formed.
I n the autoxidation of resorcinols, which was studied
in detail by MUJSO
et al. in the course of work on orcein
and litmus dyestuKs [46], biphenyl derivatives are
formed, partly by Michael addition of the resorcinols
onto quinones which are formed as intermediates. An
example of this is the formation via (59) of (60) in the
oxidation of orcinol (58) [47,48]. The process largely
corresponds to the oxidation of $-naphthol to (57).
Hydroquinones can be used as starting materials in
syntheses with nascent quinones. However, in special
cases it is also possible to produce the hydroquinones
in situ, e.g. by hydroxylation of phenols.
5. Special Cases
Model investigations on the oxidation of tyrosinase led
Brackman and Huvinga to remarkable and preparatively
valuable results [44].The Cu(l1)-catalysed autoxidation
of phenols in the presence of secondary amines proceeds
smoothly to yield aminoquinones. Phenol itself condenses with morpholine to give (55), and the corresponding reaction with P-naphthol yields (56). Many
other examples are quoted in the original publications
These processes are closely related to the reactions which
lead to the characteristic “blue color of F-tetralone”
[49]. It was shown [50], that autoxidation of $-tetralone
(61) in alkaline solution yields the dyestuff (62) as red
crystals; the inesomeric anion is deep indigo blue; cf.
(42) and (44).
The reaction mechanism was proved by the addition
of labeled and normal 9-naphthoquinones, and the
constitution of the dyestufr (62) was determined by dehydrogenation to (57).
0 7
(55), 6 4 %
(561, 8.1%
The course of these reactions is clear: o-hydroxylation of
the phenols, dehydrogenation of the resulting catechol
derivatives to o-quinones, and single or double addition
of amines onto the latter (cf. Section 2c).
The oxidation of $-naphthol with H202 catalysed by
molybdate, leads to the formation of (57) [45]. This
[42] Cf. L. Horner and W. Diirckheimrr, Chem. Ber. 95, 1219
(1962), where references to earlier literature are given.
[43] H . Musso, Angew. Chem. 75, 965 (1963); Angew. Chem.
internat. Edit. 2, 723 (1963).
[44] W. Brackman and E. Havinga, Recueil Trav. chim. Pays-Bas
74, 937, 1021, 1070, 1100, 1107.(1955).
[45] I. D. Ruacke-Fels, C. H . Wang, R. K. Robins, and 3. E. C h i stensen, J. org. Chemistry 1 5 , 627 (1950); A . R . Buder, J . Amer.
chem. Soc. 73, 3731 (1951).
6. Biochemical Examples
Nowadays, many biosyntheses are known to pass through
quinoid intermediates. T h e present knowledge of t h e formation of melanin a n d humic acid was recently reviewed by
1461 H . Musso et al., Angew. Chem. 73, 665 (1961).
1471 U . v. Gizycki, Ph. D. Thesis, Universitat Marburg 1963.
[48]H . MUSSO,
Angew. Chem. 75, 965 (1963); Angew. Chem.
internat. Edit. 2, 723 (1963).
1491F.Stmus andA.Rohrbacher, Ber. dtsch.chem.Ges.54,46( 192 I ) .
[50]H.- W. Wunzlick, M . Lehmann-Horchler. and S . Mohrinann,
Chem. Ber. 90, 2521 (1957).
A n g e w . Chem. internnt.
Edit, Val. 3 (1964) No. 6
Thomson [51]. T h e function o f nascent quinones in t h e
pupation of insects (sclerotization), which is compared with
tanning by quinones (cf. [53]), is also dealt with in this article.
Other examples, with references, m a y be found in reviews
by Mrrsso [48] and vun T a m e b n [54]. T h e biological significance of t h e phenoxazone syntheses discussed in Section 3
a n d t h e model experiments on the formation of melanins
(Section 4) have already been referred t o 1321.
The investigations of Freudenberg et al. on the biosynthesis of lignin have brought to light the importance
or quinone methide structures which occur there as
intermediates [ 5 5 ] . One example of this is the condensation of two coniferyl alcohol units (63) with the
elimination of hydrogen to form inter alia dehydrodiconiferyl alcohol (65), a reaction which can also be
carried out in vitro [56]. One-electron oxidation of the
phenol group in (63) and dimerization of the mesomeric
free radical produced yields the quinone methide (64)
which is then converted into (65) by intramolecular
even partial methylation in the catechol residue, as was
shown by Geissnian et al. [57]
The strong tendency of quinonoid systems to undergo
additions is shown by the fact that the reaction (66) +
(69) proceeds readily in vitro and requires no catalyst,
whilst the conversion of butein (66) into the flavanone
butin (68) requires the usual treatment with hot mineral
acid [60]. The polarization of the double bond initially
present in the chalcone is not only reversed in the
reaction leading to (67) but is also considerably intensified.
7. Concluding Remarks
The formation of lignin also involves intermolecular
additions onto quinone methides, in which water, acids,
phenols, alcohols, and carbohydrates participate competitively as nucleophilic reagents [ 5 5 ] .
In the formation of a u r o n e s from chalcones, which is
exemplified here by the conversion of butein (66) into
sulfuretin (69) [57], intervention of o-quinonoid intermediates is indicated by two findings: 1 . all the naturally
occurring aurones known to date [ 5 8 ] (including bractein [59], which has only recently been isolated) contain
a catechyl group; 2. The formation of aurones, which
proceeds extremely easily even in vitro, is blocked by
1511 R . H.Thomson in 1521.
[52] Recent Progress in the Chemistry of Natural and Synthetic
Colouring Matters. Academic Press, New York 1962.
[53] Cf. P. KarIson, Angew. Chem. 75,261 (1963); Angew. Chem.
internat. Edit. 2, 175 (1963).
1541 E. E.vunTamelen, Progr. Chem. org. nat. Prod. 19, 242
(1961), particularly p. 281 et seq.
1551 K . Freudenberg, Progr. Chem. org. nat. Prod. 20, 41 (1962),
where further references are given.
[56] K. Freudenberg and H . H. Hiibner, Chem. Ber. 85, 1181
(1952); see also K. Freudenberg, G. G r i m , and J . M . Harkin,
Angew. Chem. 70,743 (1958).
1571 M . Shimokoriyama and T . A . Geissman, J . org. Chemistry 25,
1956 (1960).
[58] W. Karrer: Konstitution und Vorkommen der organischen
Pflanzenstoffe. Birkhauser, Basel 1958; T . A . Geissman: The
Chemiftry of Flavonoid Compounds. Pergamon Press, London
[59] R . Hansel. L. Lunghummer, and A. C. Albrecht, Tetrahedron
Letters 1962, 599.
Angew. Chem. internat.
Edit./ Vol. 3 (1964) I No. 6
The reactions discussed here offer rewarding exercises
to the theoretical chemist. Even the addition mechanism, which is generally accepted nowadays, and
which has been used in the present article, does
not appear to have yet been rigorously proved. It is also
reasonable to ask whether all the reactions discussed
here pass through the quinone stage after all, since it is
known that a semiquinone (which is often detectable
[61]) may be formed initially in the dehydrogenation
of a hydroquinone. The work of Fvanck et al. on
biogenetic-type syntheses of alkaloids [62] may be
mentioned at this point. The dehydrogenation of
/ 721
(73), up to 90%
[60] A. Guschke and J . Tambor, Ber.dtsch. chem.Ges. 45,186(1912).
1611 Cf. H. Diebler, M . Eigen, and P . Matthies, 2. Elektrochem.
65, 634 (1961), where further references are given.
[62] B. Frunck, G. Blaschke, andG. Schlinglofl; Angew. Chem. 75,
957 (1963), where further references are given; Angew. Chem.
internat. Edit. 3, 192 (1964).
Iaudanosoline methiodide (70), for example, which
leads smoothly to aporphine (71) [63] may be justifiably assumed [64] to be a free-radical reaction.
On the other hand, the dehydrogenation of laudanosoline (72), in which the nitrogen is not quaternized,
proceeds smoothly with the formation of the dibenzotetrahydropyrrocoline derivative (731, whose trimethyl
ether occurs in nature as cryptaustoline [65]; it is cer[63] B. Franck, G. Blaschke, and G. Schlinglqff,Tetrahedron Letters 1962, 439.
1641 B. Franck andG.Schling/aff,LiebigsAnn.Chern. 659,123(1962).
1651 J. Ewing, G. K. Hughes, E. Ritchie, and W. C. Taylor, Nature
(London) I69, 618 (1952); Austral. J. Chem. 6, 78 (1953).
tainly justified to include this reaction among the
quinone additions [66,67].
W e are sincerely grateful to all those who habe helped us
in word and in deed, with encouragement and criticism,
and to the Deutsche Forschungsgemeinschaft, the Fonds
der Chemischen Industrie, and to Schering A.G.
Received, December 2nd. 1963
[A 360/159 IE]
German version: Angew. Chem. 76, 313 (1964)
Translated by Express Translation Service, London
[66] R. Robinson and S. Sugasawa, J. chem. SOC.(London) 1932,
[67] C. Schopf and K. Thierfelder, Liebigs Ann. Chem. 497, 22
New Reactive Dyes
Dedicated to Professor ff. Bredereck ox the occasion of his 60th birthday
Two new groups of reactive [email protected] have been developed. One group ([email protected] dyes)
comprises compounds which contain -SO2NH- CH2 -CH2-OS03 H or -CH2-N(a1kyl) CH2-CH2-OS03H as reactive groups. The dyes of this group react with cellulose fibers
to form cellulose ethers, e.g. R-S02NH-CH2-CH~-O-cellulose.The substances in the
second group ([email protected]) consist of the amides formed from 2,3-dichloroquinoxaline6-carboxylic acid and dyestuffs containing primary or secondary amino groups.
(b) the Levafix-E d y e s containing 2,3-dichloroquinoxaline-6-carboxylicacid bound as its amide as the
reactive group.
The development of new reactive dyes requires solutions
to problems which fall essentially into two categories :
1. The discovery of reactive systems which are suitable
for incorporation into dyestuffs and which react efficiently with the substrate to be dyed under the conditions of textile dyeworks.
2. The combination of the reactive systems with dyestuffs, either already known or new, to give reactive
dyes of high fastness.
The first problem is the more difficult one, since the
reactive group both prescribes the type of dyestuff and
largely determines the properties and scope of application of the dyes obtained with it.
Our work has led to two groups of dyestuffs:
(a) the Levaf ix dyes containing the reactive group
or -CHr-N-CH2-CH2-OSO,H,
1. Reactive Dyes with Sulfatoalkyl Groups
Activated by Neighboring Groups [*I
In 1940, H. Schweirzer and 0. Bayer described dyes
containing N-(P- or y-chloroalky1)sulfonamido groups
which imparted colors to wool [l] more wash-fast than
comparable deyings. The action of alkalies on N-(Pchloroalky1)sulfonamides ( I ) readily produces N,Nethylenesulfonamides (2) [2], which react with primary
or secondary amines - probably also with the amino
groups in wool - to effect alkylation to form (3) [3].
[*I Based o n work by K.
G. Kleb.
[l] H . Schweitzer and 0. Bayer, German Patent 143766 (April
19th, 1940); cf. 0. Bayer, Angew. Chem. 73, 343 (1961).
[2] J . Nelles and E. Tietze, German Patent 698 597 (Feb. 8th,1939).
[3] J . Nelles, E.Tietze, and 0. Bayer, German Patent 695331
(April 29th, 1939).
Angew. Chem. internal.
Edit.1 Val. 3 (1964) / No. 6
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