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New Donor-Substituted Vinyl- and Alkynylcyclopropanes as Synthetic Building Blocks.

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-20°C' for 24 h , a n d the work-up carried out below -40"C, only Sa
wa5 formed (98Yn yield). Complexea Sa a n d Sb have spectroscopic features similar to 4 : the isomers can be easily distinguished by their "PR coupling patterns in the "P{'HJ-NMR spectrum. Correct elemental
iinalyses were obtained.
P. G. Pringle, 5. 1.Shaw, J. Chem. Soc. Daiion Trans. 1983, 889.
P. Braunstein, C . d e Meric d e Bellefon, M. Ries, J. Organomei. Chem.
262 (1984) c' 14.
Eur. Pat. 87347 (Atochern).
M. C. Grossel, R. P. Moulding, K. R. Seddon, J . Organornet. Chem. 253
(1983) C 5 0 .
,',i
171
[81
[9]
[lo]
New Donor-Substituted Vinyl- and
Alkynylcyclopropanes as Synthetic Building
Blocks**
By Schahab Keyaniyan, Michael Apel,
Joe Pierce Richmond, and Armin de Meijere*
Dedicated to Professor Wolfgang Liittke on the occasion
of his 65th birthday
The vinylcyclopropane-cyclopentene rearrangement is
one of the most versatile methods for the annelation of
five-membered rings."] Enhancement of the rate of this
reaction by electron-donating substituents in the I-[*] and
especially in the 2-p0sition[~Iof the cyclopropane ring is in
the extreme case of 2-vinylcyclopropanolates so pronounced that cyclization occurs at room temperature. In
order to extend the usefulness of the (haIo~inyl)-[~]
and alkynylcyclopropanes[51developed by us, we have sought access to the corresponding donor-substituted building
blocks, examples of which include compounds 3, 11 and
7.
Ethyl vinyl ether and other enol ethers polymerize upon
heating with tetrachlorocyclopropene. On the other hand,
a-elimination of I , 1,3,3-tetrachloropropeneproduced the
carbene 1,3,3-trichloro-2-propenylidene,which added to
ethyl vinyl ether to give 1 -chloro- I-(2,2-dichlorovinyl)-2ethoxycyclopropane 2 (46%,E/Z= 2.0)14" (Scheme I). As
in the case of I-chloro- I -(trichlorovinyl)cyclopropanes,f5J
reaction of 2 with MeLi followed by quenching with electrophiles affords substituted alkynylcyclopropanes such as
1 (57%, with Me,SiCl).['I However, the yield upon reduction of 1 to 4 was disappointing (30%).
A substantial improvement was achieved by the newly
developed sequence in which the ring chlorine in 2 is selectively removed by ultras~nication['~
with zinc/copper to
yield 3 (82%, E / Z = 1.0) without retention of configuration.18]The dehydrochlorination of 3 to give the chloroacetylene 6 was best achieved['] (77%, E / Z = 1.5) with potassium hydroxide in CH,C12/dibenzo-[ 18]crown-6.["'] Reaction of 6 with lithium dialkylamides affords ynamines'"]
such as 8 (38%, not optimized, E / Z = 1.0). Halogen-metal
exchange followed by substitution with electrophiles converted 6 via 5 into synthetically interesting building blocks,
the I-alkynyl-2-ethoxycyclopropanes 7 (7a, 590/0, E/
Z=O.5; 7b, 78%, E/Z=0.83).[61 The diastereomers of 7b
could be separated by chromatography on silica gel.
Surprisingly, the addition of thermally ring-opened tetrachlorocy~lopropene[~"
h1 to vinyl acetate was achieved
without polymerization and afforded 10 (85%, E/Z= 0.61),
which could be selectively reduced to 2-(trichlorovinyl)cyclopropyl acetate 11, a potential precursor to building
blocks analogous to 7 and 8 (Scheme 2).
OEt
"
H
b)
3
2
CI
12
13
6
14
0
0
II
'
15
SiMq
"1
g,
EtO
I
EtO
\
E
7a. E = H
7b, E = C02Me
/EI-17/1ZI-i7
r
'
18
NEt2
8
1
n
0
19
Scheme 2. a) Tetrachlorocyclopropene, 155'C. 36 h. b) Zn/Cu, T H F / H 2 0
@/I),
ultrasonication, 6 5 T , 20 h. c) C O ~ ( C O )CO,
~ , 120"C, 48 h. d ) 600"C,
0.1 torr, 0.09 s. e) ( E ) : 125"C,
135°C. f , E t 2 0 , 2 i i HCI, RT. g) 250"C, 0.02
torr, 0.8 s.
(a:
Scheme 1. a) I ) MeLi, tetrahydrofurdne (THF), - 3 5 ° C ; a ) Me3SiCI,
-35°C-RT.
b) Z n / C u , T H F / H 2 0 @ / I ) , ultrasonication, 6 5 T , 20 h. c)
LiAIH,, T H F , A, 10 h. d) KOH, CH2CI2,dibenzo-[18]crown-h, 24 h. e) nBuLi,
THF/n-hexane, -78°C. f ) M e O H (-7a); CICOzMe (-7b). g) LiNEt2,
Et,O, -20°C.
[*I Prof. Dr. A. d e Meijere, Dr. S . Keyaniyan, M. Apel, Dr. J .
[**I
770
P. Richmond
Institut fur Organische Chemie der Universitat
Martin-Luther-King-Platz 6, D-2000 Hamburg 13 (FRG)
This work was supported by the Deutsche Forschungsgerneinschaft, the
Fonds der Chemischen Industrie, a5 well as by a NATO Research
Grant, Hoechst AG, a n d BASF AG. We thank Prof. I . Erden for helpful
discussions.
0 VCH Verlagsgerellrchafr mhH, 0-6940 Weinheim, 1985
Cycloadditions to the triple bond of such alkynylcyclopropanes afford vinylcyclopropanes[12] in which the vinyl
group is incorporated into a ring and whose rearrangement
to a cyclopentene should be facilitated by the 2-ethoxy or
the 2-acetoxy function.
Thus reaction of (E/Z)-7a with cyclopentene 12 and
C O ~ ( C Ounder
) ~ CO (cf. [I3') followed by chromatographic
separation gave a 1 : 1.6 mixture (30%) of both diastereomers of 3-(2-ethoxycyclopropyl)-cis-bicyclo[3.3.0]oct-3-en-2-
0570-0833/85/0909-0770
S 02.50/0
Anyew. Chern. Ini. Ed. Engl. 24 (19851 No. 9
one, ( E ) -131"'with ( E ) configuration on the 3-membered
ring and a 1 : 1 mixture (4Yo) of both diastereomers of (2)13. Reaction of pure (E)-7b with I-cyclopentenylpyrrolidine 15 at 125°C furnished the cycloheptadiene derivative
(E)-16 (55%); ( 9 - 7 b was converted at 135°C into (2)-16
(47%). The enamines 16 can be hydrolyzed to the methyl
7-0x0-2-cycloheptene- 1 -carboxylates (E)-17 (16%) and
(917 (37%),['] respectively.
Upon flash vacuum pyrolysis, 13 is smoothly converted
into the linearly annelated triquinane 1416'(39% after chromatography on SiO,).["I Product 14 consisted of three stereoisomers in a ratio of 4 :2 : 1, whose separation thus far
has been achieved only by capillary gas chromatography.
According to 'H-, 'H,H-COSY- and 'H,"C-correlationNMR spectra, the ratio of anti- and syn-configurated isomers is 5 : 2 or 3 :4. The cycloheptene derivative, (2)-17,
rearranges especially easily; evidently the main reason for
this is that the B-ketoester splits off methanol above 250"C,
forming the ketoketene 18,['4~151
which, due to favorable
stereochemistry, can cyclize with ethoxy-group migration
to give ethyl 3-oxobicyclo[5.3.0]deca-1,9-diene-2-carboxylate 19.
Received: October 16, 1984;
revised: June 25, 1985 [Z 1040 IE]
German version: Angew. Chem. 97 (1985) 763
[I] Reviews: M. Ramaiah, Synthesis 1984. 529: R. F. C. Brown: Pvrolytic
Methods in Organic Chemistry. Academic Press, New York 1980, p.
309 ff.
[2] Cf. B. M. Trost, P. H. Scudder, J. Org. Chem. 46 (1981) 506.
[3] H. G. Richey, Jr., D. M. Shull, Tetrahedron Letf. 1976, 575.
[4] a) W. Weber, A. d e Meijere, Angew. Chem. 92 (1980) 135; Angew. Chem.
Int. Ed. Enyl. 19 (1980) 138; b) W. Weber, A. d e Meijere, Chem. Ber. 118
(1985) 2450: c) W. Gothling, S. Keyaniyan, A. de Meijere, Tetrahedron
Lett. 2.5 (1984) 4101.
[5] a) T. Liese, A. de Meijere. Angew. Chem. 94 (1982) 65; Angew. Chem.
Int. Ed. Engl. 21 (1982) 65; Angew. Chem. Suppl. 1982, 34; b) T. Liese,
G. Splettstosser, A. de Meijere, Tetrahedron Lett. 23 (1982) 3341.
[6] All new compounds were unequivocally characterized by their IR, 'HNMR, and where necessary, "C-NMR spectra; in most cases satisfactory elemental analyses were obtained. Examples: 13: IR (film):
~ = 3 0 3 0 - 2 8 5 0 (C-H), 1700 (C=O), 1630 (C=C), 1200-1020 (C-0)
cm - I , ' H - N M R 1270 MHz, CDCI,): 6=0.90-1.00 (m, I H, 3'-H,,), 1.101.20 (m, I H , 3'-Hh), 1.20 (t, 'J=7.0 Hz, 3 H , 2"-H), 1.50-1.95 (m, 7 H ,
6,7,8,1'-H), 2.70-2.80 (m, I H, I-H), 3.10-3.20 (m, 1 H, 5-H), 3.25-3.35
(m. 1 H, 2'-H),3.48+3.59(q+mc,2H,int. ratio I:l.6, I"-H),6.74+6.77
( 2 d , I H, 'J=3.5 Hz, int. ratio 1.6: I , 4-H); MS (70 ev): m / z 206
( M ' ) - 14: IR (film): v=3030-2850 (C-H), 1700 (C=O), 1620 (C=C),
1150- 1020 ( C - 0 ) c m - ' : ' H - N M R (400 MHz, C,D,): 6=0.83-2.00 (m,
6 H , 9,lO,Il-H), 1.04, 1.10, 1.13 (3t, ' J s 7 . 0 H z , 3 H , int. ratio 1 : 2 : 4 , 2'H), 2.00-2.40 (m, I H, 8-H), 2.40-2.70 (m, 3 H, 1.4-H), 2.64-3.32 (m, 3 H,
2,l'-H), 3.66, 3.72, 3.88 (3 mc, 1 H, int. ratio 1 :2:4, 3-H),6.01, 6.08, 6.17
(3mc. 1 H, int. ratio 2 : 4 : I,5-H); MS (70 eV): m / z 206 ( M + ) - ( . Z - 1 7 :
IR (film): v=3400 (0-H), 3030-2850 (C-H), 1640 (C=O), 1590 (C=C),
1240, 1030 ( G O ) c m - ' : 'H-NMR (270 MHz, C,D,): 6 ~ 0 . 6 1(ddd,
'J=.SX Hz, 'J(1'.3'E)=9.6 Hz, 'J(2',3'E)=6.2 Hz, 1 H, 3'-H(E)), 0.70
(ddd. 'J(1',3'2)=7.0 Hz, 'J(2',3'Z)=3.6 Hz, I H, 3'-H(Z)). 1.02 (X component of an ABX, system, './(AX)= 'J(HX)=7.0 Hz, 3 H, OCHICHI),
1.75 2.03 (m, S H , 5,6,I'-H), 2.25-2.58 (m, 2 H , 4-H), 3.04 (ddd,
'J(1',2')=6.4 Hz, I H, 2'-H), 3.30 (AB component of an ABX, system,
2 H , OCH,CH,), 3.36 (s, rel. int. 0.5, I-H), 3.37 (s, 3 H ) , 5.93 (mc, I H, 3H), 7.44 (bs, rel. int. 0.5, enol-H).- 19: IR (film): v=3030-2830 (C-H),
1710. 1640 ( C = O ) , 1600 (C=C), 1220, 1180, 1020 ( C - 0 ) c m - ' ; 'HNMR (270 MHz, C,D,): 6=0.84 (mc, 1 H, 6-H,,), 0.96 (X component of
an ABX, system, 'J(AX)='J(BX)=7.0 Hz, 3 H, 3'-H), 1.08-1.20 (m, 2 H ,
5-H,, h-H,,), 1.35 (mc, 1 H, 5-H,), 1.50 (dddd, 'J= - 19.2 Hz,
'J(Xa.7)= 1.8 Hz, 'J(8a,9)=2.2 Hr, 'J(Sa,I0)=2.8 Hz, I H, 8-H,,), 2.032. I 8 (m, 2 H, 4-H,,, 8-H,), 2.27 (mc, 'J= - 15.2 Hz, 1 H, 4-Hb), 4.1 I (AB
component of an ABXi system, 2 H , 2'-H), 5.96 (ddd, 'J(c;s)=5.5 Hz,
JJ(10.Xa)='1J(10,8b)=2.8
Hz,
I H,
10-H),
6.81
(ddd,
'J(B.Xn)='J(9,8b)=2.2
Hz, 9-H): MS (70 ev): m / z 220 ( M + ) , 151
(M-C'?H<)*.
[7] Simple heating of 2 with Zn/Cu couple in T H F / H 2 0 did not lead to reduction as described for 7.7-dibromonorcardne (R. M. Blankenship, K.
A. Burdett. J. S. Swenton, J. Org. Chem. 39 (1974) 230). The selective reduction of 2 with Zn/Cu in a laboratory cleaning bath (Bandelin, Mod.
R K 2 2 5 ) is a further example of the utilization of ultrasound-activated
Angew. Chem. Int. Ed. Engl. 24 (1985) No. 9
zinc in organic synthesis (cf. B.-H. Han, P. Boudjouk, J. Ory. Chem. 47
(1982) 751, 5030).
[XI Similar reduction of ( a - 2 gave a I : I mixture of ( E ) - and (2)-3.
[9] With the method described for other chloroacetylenes (LiN Et2, Et'O,
-78°C: J. Villieras, P. Perriot, J. F. Normant, Synthesis 1975. 458) the
maximum yield of 6 was 56%.
[lo] Based o n the method of: E. V. Dehmlow, M. Lissel. Liebigs Ann. Chem.
1980, I ; Tetrahedron 37 (1981) 1653.
[ 1 I] Cf. L. Brandsma: Preparative Acetylenic Chemistry, Elsevier, Amsterdam
1971, p. 85; S. Y. Delavarenne, H. G. Viehe in H. G. Viehe (Ed.): Chemistry of Acetylenes, Marcel Dekker, New York 1969.
[I21 G. Splettstosser, S. Keyaniyan, A. de Meijere, unpublished results: G.
Splettstosser, Disserfatron. Universitat Hamburg 1985.
[ 131 Analogously synthesized compounds of type 13 without electron-donating substituents required up to 150°C higher pyrolysis temperatures under otherwise identical conditions; J. P. Richmond, T. Liese, A. d e Meijere, unpublished results.
[I41 Cf. C. Wentrup, K.-P. Netsch, Angew. Chem. 96 (1984) 792; Angew.
Chem. I n t . Ed. Engl. 23 (1984) 802.
[I51 a-Ketoketenes of type 18 were detected in the pyrolysis of 17-analogues
without the ethoxy substituent (cf. [ 121).
Heterogeneous Redox Catalysis on
Ti/Ti02 Cathodes-Reduction of Nitrobenzene**
By Fritz Beck* and Wolfgang Gabriel
Reductions with low valency titanium compounds are
well known in organic chemistry. Typical examples are,
inter alia, the reduction of nitro compounds with
and the reductive dimerization of ketones to olefins with
Stoichiometric quantities of reducing agent were
used in these reactions. The selectivity of the processes is
explained in terms of a complexation of the reactants with
the titanium species. Since large amounts of reagents such
as TiCI, are not easy to handle, it was suggested that the
reduction be carried out on an inert cathode in the presence of a dissolved redox mediator such as (TiO)S0414'11
or
TiC14.[4b1We report herein on a further simplification,
namely the oxidic Ti-redox system fixed to the surface of a
Ti cathode.
The Ti/Ti02 electrode was fabricated using a method
employed in the production of ceramic^.^"^ As shown by
the cyclic voltammograms la, b in Figure 1, reduction of
the surface layer starts at ca. U H= - 0.1 V with respect to a
standard hydrogen electrode. This corresponds to the
equilibrium potential for Reaction (a):["
Ti(OH),
+ e0 + H e
------)
Ti(OH),
+ H,O
(a)
At more negative potentials, further reduction processes
come into operation, with a current maximum at
UH= - 0.73 V and a shoulder at UH= - 0.65 V. Whether
Ti1v/Ill
transitions, e.g. Reaction (b),
+
+
TiOz + HZO H@ e 0
-
Ti(OH),, UH.o= -0.79 V
(b)
or Til11/11 redox processes operate,@'both of which are possible in this voltage range, cannot be decided with certainty. At still more negative potentials, cathodic evolution of
hydrogen begins to take place (Fig. I , 8). The corresponding re-oxidation processes are detected cyclovoltammetrically. The Ti02 layer is converted up to 2-20%, a relatively
high value for a solid-state reaction, the conversion decreasing with increasing voltage scan rate. The redox processes can be repeated as often as desired. At higher pH val[*I Prof. Dr. F. Beck, DipLChem. W. Gabriel
FB 6- Elektrochemie der Universitat-Gesamthochschule
D-4100 Duisburg 1 (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
0 VCH Verlagsgesellschaft mbH. 0-6940 Weinhelm. 1985
OJ70-0833/85/1)909-0771 $ 02.50/0
71 1
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