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Cross-Conjugated Trienes by Thermal Isomerization of Alkynes.

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One-Pot Synthesis of 1-Alken-5-yne Derivatives[']
[3] 0. Grummitt, E. P. Budewitz, C. C. Chudd, Org. Synfh. Coll. Vol. 4 (1963)
749.
141 The use of propargyl chloride 4 is decisive, since 4, in contrast to the corresponding bromide, does not react with the excess magnesium present in
ether.
151 All the new compounds were characterized by the usual spectroscopic
methods and by elemental analysis.
By Hanno Priebe and Henning Hopf *
Propargyl halides 1 metalated in the 3-position are equivalent to the zwitterion 2, a species suitable for use as a
functionalized C,-synthon for the synthesis of complicated
carbon frameworks since it should couple with both electrophilic and nucleophilic substrates:
M-C--C-CH2-Hal
1
P
"C=C-CHF
Cross-Conjugated Trienes by Thermal Isomerization
of Alkynes"]
2
By Hanno Priebe and Henning Hopf *
Although simple cross-conjugated polyolefins such as 2vinyl-1,3-butadiene 1 and 3,4-bis(methyIene)-l,S-hexadiene 2 ( = 3, n = I ) have been known for some time, the homologous series of hydrocarbons 3 ("dendralenes") beginning with these substances has been neglected until
As shown by the following one-pot reaction for the synthesis of I-alken-5-yne derivatives 9 , this is indeed the case
even if the reactive centers in 1 are not activated simultaneously, but successively. The compounds (see ['I) can be
readily prepared if two equivalents of allylmagnesium
bromide 3f31react first with propargyl chloride 4L4].
Thereby 5-hexen-1 -ynylmagnesium bromide 7 is formed
in almost quantitative yield via 5 (type 112) o r 6; 7 reacts
with electrophilic reagents 8 to give the desired products
IIOW[~~.
9151.
2 H,C=CH-CH,MgBr
+ HC-C-CH,Cl
4
3r-----l
+
5 [MgBr-C- C-CH2C1]
H,C=CH-CH,CH,-CsC-MgBr
1+?-?8
9 H,C=CH-CH,CH,-CZC-E
E-X
H20
CHzO
CHKHO
C2HSCH0
(CH&C H-CHO
HzC=CH-CHO
(CH a)>C=O
(CH,),C=O
H,C=CH--CO-CH,
(CHx)>N-CHO
(CH3CO)20
co,
(CHAO
7
r
1
+ MgBrX
-E
8
6
(H2C=CI-I-CH2CH2-C-CH]
For the synthesis of dendralenes, classical reactions such
as eliminations and condensation^^'^ are preferred. In addition to a novel route to 1 , we also report the synthesis of
the conformationally partially fixed 2-vinylbutadiene 4.
Both syntheses are related to each other in the sense that
the educts already contain the desired number of rc-electrons and carbon atoms. Compound 4 is of interest for the
investigation of a novel degenerate 8n-isomerization (automerization) via diradical 5.
in 9
-H
-CHZOH
-CH(OH)CH3
-CH(OH)C2H5
-CH(OH)-CH(CH3)2
--CH(OH)-CH-CH>
-C(OH)(CH3)2
--C(OH)(CHz),
--C(OH)CH,(CH=CH>)
-CHO
-CO-CHI
-C02H
-CH,CH2-OH
Yield
4
[%I
5
93
[&]
18
50
32
45
31
83
35
22
H
3 , n = O , l , 2 ...
n = 1:2
13
12
15
17
63
13
A first impression of the scope of application of the
method is given by the tabular summary of reactions,
whose yields except for the reaction of 7 with acetone
have not been optimized. The Grignard reagent 3 and the
coupling component 4 can be varied: for example, ethylmagnesium bromide, 4 , and acetaldehyde produce 3-heptyn-2-01 (22%)["; 7-octen-3-yn-2,5-dioI (36%) is formed
from 3, propionaldehyde, and acetyldehyde.
Received: August 21, 1981 [Z 45a IE]
German version: Angew. Chem. 92 (1982) 299
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982, 635-639
D
9
10
A: I . Mg/ether, 2. CuC1.3. + S (6O%total yield); 8: 500"C, 4!%; C: LindlarHz. 60%; D: TsOH, 120-150°C/100 tom, 24%; E: 400-500°C; F: 440°C.
'H-NMR data for 4 (CDC13): 6=2.43 (m; ZH")),2.64 (m.2H7), 4.84 (m, H'),
4.99 (dtt, H5, J5,=2.6,J,,=l.l
Hz), 5.17 (dm, H4), 5.53 (dm, H3). 6.21 (ps,
H2), 6.39(dddt, HI, J13=17.6, Jlq=lI.I, JIx=0.8, J,1=1.1 Hz).
For the preparation of 1, propargyl bromide 8 is dimerized to 1,2-hexadien-5-yne 7, which is subsequently isomerized at 500 C to 2-ethynyl- 1,3-butadiene 6 ; Lindlar hydrogenation of 6 then affords ll5].
The starting material for 4 is 1,7-octadien-3-yne 10,
which is obtained from the alkenynyl alcohol 919]by acid
O
[ I ] Alkynes and Cumulenes. Part 16.-Part 15: H. Hopf, H. Siegel, L. Eisenhuth, Chem. Ber. 114 (1981) 3772.
121 H. Priebe, H. Hopf, Angew. Chem. 94 (1982) 299; Angew. Chem. I n [ . Ed.
Engl. 21 (1982) 286
[*I
Prof. Dr. H. Hopf, H. Priebe
Institut fur Organische Chemie der Technischen UniversitBt
Schleinitzstrasse, D-3300 Braunschweig (Germany)
286
0 Verlag Chemie GmbH, 6940 Weinheim. 1982
[*] Prof. Dr. H. Hopf, H. Priebe
lnstitut fur Organische Chemie der Technischen UniversitAt
Schleinitzstrasse, D-3300 Braunschweig (Germany)
0570-0833/82/0404-0286 $02.50/0
Angew. Chem. In[. Ed. Engl. 21 (1982) No. 4
catalyzed dehydration. 10 isomerizes to the allene 11uia a
Cope rearrangement (400-500 C). As expected[''] 11
reacts to give the diradical 12, which stabilizes itself by a
1,2-hydrogen shift to yield 4 and its nonconjugated isomer
13. Whereas at 440°C, 44% 4 and 52% 13 are produced
(rest 10 and 11, GC), 13 is practically the only rearrangement product at 500°C (93%, rest 4).
The structural assignments for 4 are based on 'H- and
I3C-NMR data, as well as on vibrational- and electronicspectra [acetonitrile, A,, = 252 nm (log&=3.7)]. In comparison to the conformationally less restricted 1
= 224 nm (logs = 4.411, 4 exhibits a bathochromic
shift which almost corresponds to that of the completely
fixed 3-methylene-1,4-cyclohexadiene [A,;,%= 242, sh at
247 nm (log&=4.41'21)].
Pyrolyses of methyl derivatives of 10 result in the corresponding derivatives of 4 and 13. Moreover, since a further cross-conjugated triene (1,2-dihydropentalene) can be
synthesized by thermal rearrangement of 1,2-diethynylcyclobutane, the thermal rearrangement of alkynes promises
to become a useful method of preparing branched polyolefins.
Received: August 21, 1981 [Z 45b IE]
German version: Angew. Chem. 92 (1982) 299
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982, 640-645
[I] Thermal Isomerization, Part 10.-Part 9: H. Priebe, H. Hopf, R. Walsh,
J. Am. Chem. SOC.I02 (1980) 1210.
[5] The most comprehensive discussion of the spectroscopic properties of
cross-conjugated polyolefins (incl. 1) to date, may be found in the dissertation of A. Cassens (Universitat Gottingen, 1979), in which the synthesis of several dendralenes with Axed structures is also described. Cf.
also: J. Kindler and J. Janson, dissertations, Universitat Gdttingen 1975
and 1979, respectively. Prof. Dr. W. Liittke is thanked for supplying copies of these theses and for further literature references.
[9] H. Priebe, H. Hopf, Angew. Chem. 94 (1982) 299; Angew. Chem. Int. Ed.
Engl. 21 (1982) 286.
[lo] a) V. Dalacker, H. Hopf, Tetrahedron Lett. 1974. 15; b) W. D. Huntsman, J. A. De Boer, M. H. Woosley, J . Am. Chem. SOC. 88 (1966)
5846.
[I21 H. Plieninger, W. Maier-Borst, Angew. Chem. 75 (1963) 1177; Angew.
Chem. Inr. Ed. Engl. 3 (1964) 62.
Geminal Vinyl Diazides: Potential Precursors of
Functionalized Alkylidenecarbenes;
Synthesis and Reactions of
3,3-Diazido-2-cyanoacrylic Acid Methyl Ester**
By Robert CarriP. Daniel Danion, Erich Ackermann,
and R o y W. SaaIjirank*
So far very little is known about heteros~bstituted~~~
or
fun~tionalized'~~
unsaturated carbenes. We have now investigated 3,3-diazido-2-cyanoacrylicacid methyl ester 6 as
potential precursor of cyano(methoxycarbony1)vinylidene
13.
W. Saalfrank, E. Ackermann
Institut fur Organische Chemie der Universitat Erlangen-Niirnberg
Henkestrasse 42, D-8520 Erlangen (Germany)
Prof. Dr. R. Carrie, Dr. D. Danion
Groupe de Recherches de Physicochimie Structurale
Faculti des Sciences de I'Universite
B. P. 25 A, F-35042 Rennes (France)
Geminal Vinyl Diazides, Part 1 (Part of a Dissertation by E. A . (1981)).
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie. R . W.S. thanks the University of
Rennes for a visiting Professorship.
[*] Prof. Dr. R.
[**I
Angew. Chem. Int. Ed. Engl. 21 11982) No. 4
A solution of 0.5 g of 3,3-dichloro-2-cyanoacrylicacid
methyl ester191in a small amount of acetone is added at
- 15 "C to an excess of sodium azide dissolved in acetone/
water (1 :1). After a few seconds spectroscopically pure,
pale yellow-green crystals of the ester 6 precipitate from
the solution [UV (CH30H): A,,, = 304, 244 nm (Ig&=4.34,
4.1 O)].
6
7, X = OCH,
10, X = CN
9
On addition to methanol at just below the boiling point
6 decomposes with vigorous evolution of N2; subsequent
removal of methanol and recrystallization of the residue
from diethyl ether afford colorless crystalline 2-(N-cyanimino)-2-methoxyacetic acid methyl ester 7 [yield 75%; m. p.
54°C; 'H-NMR (CDC13): 6=3.96, 4.00 (s, 6 H , CH3); I3CNMR (CDCI,): 6=54.36, 57.94 (9, CH3; 'JCH=150 Hz),
110.23 (s, CN), 155.38, 164.57 (q, C=Nand C=O resp.,
3JcH= 4 Hz].
We assume that on heating, 6 initially undergoes a 3,5ring-closure with N,-eliminati~n"~~.
The resulting azidoazirine 9 then undergoes further loss of N2 and rearrangement to form the ester
which, on addition of methanol and elimination of hydrogen cyanide affords 7. The
intermediate 10 can be trapped with 2,3-dimethylbutadiene to give a tetrahydropyridine derivative uiu a DielsAlder reaction.
HHc02cH3
H3C0
CN
12
N*=C
=(
: C C CN
ozCH3
13
CO,CH,
CN
16
Irradiation (3 h, Original Hanau, high-pressure radiation
lamp TQ 150) of 6 in methanol at -30°C affords 7 (700/0)
together with the photoproduct 12 (30%).
The 2-cyano-3-methoxyacrylic acid methyl ester 12
probably results from an insertion of the intermediate alkylidenecarbene 13 into the H-0 bond of methanol. It is
still unclear, however, which other intermediates are involved in the formation of 13. A further possible route to
the vinyl ether 12 is the addition of methanol to the diazoethene 1616]to give the corresponding vinyldiazonium
methoxide, followed by decomposition.
Received: September 16, 1981 [Z 46a IE]
revised: February 9, 1982
German version: Angew. Chem. 94 (1982) 293
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982. 660-667
[4] S. Y. Delavarenne, H. G. Viehe, Chem. Ber. 103 (1970) 1209.
[5] M. Carion, Bull. SOC.Chim. Fr. 1969, 210.
[6] Cf. also P. M. Lahti, J. A. Berson, J . Am. Chem. SOC.103 (1981) 701 1 : W.
Kirmse, 0. Schnurr, H. Jendralla, Chem. Ber. 112 (1979) 2120.
191 R. Gompper, R. Kunz, Chem. Ber. 99 (1966) 2900.
1131 Cf. also R. Huisgen, Angew. Chem. 92 (1980) 979; Angew. Chem. Int. Ed.
Engl. 19 (1980) 947; H. Bock, 6. Solouki, ibid. 93 (1981) 425 and 20
(1981) 427.
[lS] Cf. also G. Smolinsky, C. A. Pryde, J . Org. Chem. 33 (1968) 241 1.
@ Verlag Chemie GmbH, 6940 Weinheim. 1982
0570-0833/82/0404-0287 $ 02.50/0
287
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