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Linkage of Alkyl Groups through Arenofunctional Groups.

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Linkage of Alkyl Groups through
Arenofunctional Groupsr [**I
unconjugated monoenes are still unsatisfactory. The proportions of (2) : ( 5 ) (Table 1, expts. 1 and 2) and of the isomers (2) (Table 1, expt. 2) can be modified by varying the
current density.
1/2 R-R
By Thomas Kaufmann and Annegret Woltermann"]
Alkyl groups are often linked through functional groups;
some important types of such linkage are shown in Table 1.
On the basis of the arenology principle''] we have investigated the possibility of effecting corresponding linkages also
through suitable hetarenes ("arenofunctional groups"[']),
and we have succeeded with types A, B, C, and E but surprisingly not with D.
R-01-01-R
Type A (-Nu-El-)
:This type of linkage of alkyl groups
by classical functional groups occurs readily. With areno-
Table 1. Important types of linkage for alkyl groups (Nu
Type (-
= alkyl)
= nucleophilic,
Through classical functional groups
El
= electrophilic center)
Through arenofunctional groups
e . g . esters
0
A
-Nu-El--
II
-0-c-
acid anhydrides
B
-
-El-Nu-El-
0
0
ll
II
--C-0-C-
diacyl peroxides
C
--El-Nu-Nu-El--
0
0
II
II
-C-0-0-Ccarbonic acid esters/urethanes
-Nu-El-Nu-
0
D
-Nu-El-Nu'-
-0-C-X-
II
(X = s, 0 )
(X = 0 or N H )
d isu 1fid e s
E
-Nu-Nu-
Electrolysis of methyl hydrogen malonate in the presence of
styrene:
A solution of styrene (80 ml), methyl hydrogen malonate
(30 g, 0.26 mol), and potassium methyl malonate (8 g, 51
mmol) was electrolyzed at 0°C at a cylindrical platinum
gauze anode (effective surface area 2.3 an') with 0.6 A and
a terminal voltage of 60 V to consumption of 0.336 F.
Distillation of the crude product up to 40-135"C/0.2 torr
afforded 9.4 g, from which compounds ( 8 ) to (10) and
(12) were separated by gas chromatography at 200°C
(column : 8 m, 10% of Apiezon M on Chromosorb P). The
distillation residue (1 5.5 g) consisted to 93% of sublimable
(11).
Received: June 28, 1972 [Z 676 1El
German version. Angew. Chem. 84. 893 (1972)
[ l ] Anodic Oxidation of Organic Compounds, Part 10.-Part
9:
H . Schafer and A. AlAzrak, Chem. Ber. 105. 2398 (1972).
[23 L. Eberson and H . Schufer, Fortschr. Chem. Forsch. 21, 1 (1971),
Table 11
131 See [2], Table 7 ; M Chkir and D. Lelundais, Chem. Commun.
1971. 1369.
842
--s--s-
functional groups, however, a dificulty arises : the slight
reactivity of nucleophilic hetarenesr3]towards electrophilic
hetarenes requires that they be first activated by lithiation.
However, since just in those electrophilic alkylhetarenes
that are readily accessible by synthesis the alkyl groups in
the a-position are relatively acidic, an undesired transmetalation occurs easily, with subsequent aromatic substitution
according to or analogous to the change (1)+(2) (in T H F
at - 65 to + 60 0C)141,i. e. there is an "arenological Claisen
reaction", as can be readily appreciated by comparing the
two sets of following formulas [yield of (2), ca. 80%; m.p.
of (2) ; 81 "C].
The bicyclic 10K-electron system of quinoline, with the relatively high double-bond character of its C-N bond, is
suitable for linkages of this type, for its electrophilic activity
[*] Prof. Dr. Th. Kauffmann and A. Woltermann
Organisch-Chemisches Institut der Universitat
44 Munster, Orleans-Ring 23 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft,
the Landesamt fur Forschung des Landes Nordrhein-Westfalen. and the
Fonds der Chemischen Industrie.
Angew. Chem. internat. Edit. / Vol. I1 (1972) / No. 9
resembles that of a 2n-electron system such as >C=Nor >C=O more than that of the 6x-electron system of pyridine. Unlike (1) or 2-meth~lpyridine[~',
4-methylquinoline
(3) reacts with 2-lithiothiophene to give (4) smoothly in
Types B and C (-El-Nu-Eland -El-NuNu-El-)
: 4-Nonylquinoline (6) reacts with 2-lithiothiophene in ether/hexane (5 : 1) at 0--36°C to give 58% of
( S ) , m.p. 43 "C. The lithium compound ( 9 ) obtained there-
ether/hexane (4 : 1) at 5 'Cc6, 71. Further, in T H F at - 60 "C
it is lithiated by Li diisopropylamide almost quantitatively
at the methyl group and can then be alkylated by alkyl
from by n-BuLi in ether at 5 "C (yield > 45%, proved by
addition to benzophenone; m.p. of the alcohol obtained,
1 2 6 1 2 1 "C) was treated with 1 mol of 4-nonylquinoline
1
n-BuLi
halides to afford 4-alkylquinolines [synthesis of (5) : in
T H F a t -6O"Cl.Thesecompoundscan belinked to2-hexadecylthiophene[*I, as shown by the example (5)- (7) (in
ether at 35°C) [ ( 4 ) : yield 36%, m.p. 1 2 G 1 2 1 OCL7];(6) :
yield 79% b.p. 158-159"Cj0.01 torr; (7) : yield 63%, m.p.
34 "C] .
(in ether at 5"C, after distillation of the ether in di-n-butyl
ether at 120'C). A surprisingly low yield (4%) of (10)
(m.p. 7 0 T , yellow) was thus obtained, together with unchanged starting material. However, the action of 2 mol
of CuCl, on ( 9 ) (in ether at 5°C after distillation of the
ether in di-n-butyl ether at 140°C) led to a 24% yield of
(11),yellow, m.p. 84-85°C.
Type D (-Nu-El-Nu-):
Since alkyl groups attached to
nudeuphilie hetarenes at the a-position are not acidic, the
difficulty (transmetalation and secondary reaction) mentioned above need not be feared for this type. We attempted
such a linkage by treating 2 mol of the 2-alkyl-5-lithiothiophene (5) with 2,6-dichloropyridine in ether at 35 "C and
with2,4,6-trichloro-s-triazineinether/THF(2
: 1)at - 25 "C.
Unlike the analogous treatments with 2-lithiothiophene
which gave (12) (yield 18%19] or (15) (yield 52%, m.p.
147"C[101),this reaction stopped at the biaryl stage (13)
(yield 2S%, 46°C) or (14) (yield 82%, m.p. 67-68°C).
The further reaction with (5), which could not be forced
under more severe conditions, is clearly hindered sterically
by the long alkyl groups.
Type E (-Nu-Nu-)
: Except with thiols, oxidative coupling plays only a small role for compounds Alk-Nu-H
(Nu = 0,NH, or S) because of interfering side reactions and
subsequent reactions. With the corresponding arenofunctional compounds such couplings become more
important, since nucleophilic hetarenes mostly undergo
satisfactory oxidative coupling through organocopper
Angew. Chem. internat. Edit.
Vol. 11 (1972) 1 No. 9
843
berger, and E. Wienhofer, Angew. Chem. 83, 799 (1971); Angew. Chem.
intern. Edit. 10, 744 (1971).
[2] Th. Kauffmann, Angew. Chem. 83,798 (1971); Angew Chem. internat.
Edit. 10, 743 (1971). Expanded treatment: Th. Kauffmann, Chimia, in
press.
[3] A . Albert (Heterocyclic Chemistry. 2nd Edit., Athlone Press,
London 1968; Chemie der Heterocyclen. Verlag Chemie, Weinheim
1962) recognized the two main categories of hetarenes and designated
them by the additions “n-electron excess” and “n-electron deficiency”.
Insofar a s the hetarenes act as functional groups we prefer the designations
“nucleophilic” and “electrophilic”. These expressions have no absolute
significance but denote the prevailing character.
[4J First observed (yield 85%) for the action of Li diisopropylamide
on ( I ) in ether at 35°C: H. Fischer, Dissertation, Universitat Munster
1972.
[S] Is metalated by 2-lithiothiophene on the methyl group- C. G . Screras,
J . F. Eastham, and C . W Kamienski. Chimica 24, 109 (1970).
[6] In nucleophilic substitutions with quinoline derivatives, hydrolysis
was always followed by heating a t 60°C with nitrobenzene to ensure
rearomatization.
171 J . Jackisch, Dissertation, Universitat Munster 1972.
[S] Preparation according t o E. Campaigne and J . L. Dietrich. J. Amer.
Chem. SOC.70, 391 (1948). metalation by n-BuLi.
[9] Th. Kaufmann, E. Wienhofer, and A. Woltermann, Angew. Chem.
83, 796 (1971); Angew. Chem. internat. Edit. 10, 741 (1971).
[lo] W. Brinkwerth, Dlplomarbeit, Universitat Munster 1972.
compounds, and by the synthesis of (16) (yield 66%,
m.p. 77°C) we could show that long alkyl groups hardly
hinder this type of coupling at all.
Protophanes by Oxidative Coupling of
“Transposed Dithiols”I1l[*’]
By Thomas Kuuffmann, Jorg Jackisch, Annegret
mann, and P e t e r Rowemeier“l
+
C i i , - ( C H z ) 1 5 ~ (SC H 2 ) 1 5 - C H 3
(16)
The compounds prepared, whose structural formulas are
in accord with elemental analyses and spectra (MS, NMR,
Wolter-
According to the arenology principle[2331classical functional groups of organic chemistry such as -0-H,-S-H,
-CO-X,
-CS-X,
etc., can be regarded as the first members of homologous series whose higher members (6 or
lox-electrons, etc.) consist of “arenofunctional groups”,
i.e. nucleophilic or electrophilic hetaryl groups with suitable
substituents (H or XC3])(examples: Table 1). In their rele-
Table 1. Arenology principle for functional groups (examples) [6]
Stage
Nucleophilic groups
Electrophilic groups
10-n
6-n
2 IP/nl
UV, IR), all melt sharply and usually in a favorable range ;
they are readily soluble in organic solvents and crystallize
well. Working with such arenofunctional compounds is
only little more difficult (chromatography in place of
distillation) than with normal functional compounds.
Received: July 5 , 1972 [ Z 677a IE]
German version: Angew. Chem. 84, 824 (1972)
[ l ] Protophanes and Polyarenes, Part 7.-Part
6 : Th. Kuufmonn.
Tetrahedron, in press; Part 5: Th Kaufnmnn. J. Jackisch, H.-J. Srrefr-
844
- O
S H
-S-H
vant properties[31,the higher members resemble the initial
members that are poorer by one or more units of 4x-electrons (printed bold in Table I), as shown by the comparison
in Table 2. It seems reasonable, therefore, to “transpose”[41
[*] Prof. Dr. Th. Kauffmann, Dip].-Chem. J. Jackisch, A . Woltermann,
and P. Rowemeier
Organisch-Chemisches lnstitut der Universilat
44 Munster, Orleans-Ring 23 (Germany)
[“I This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie.
Angew. Chem. internat.
Edit. / Vol. I I (1972) / No. 9
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