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Enantioselective Wagner-Meerwein Rearrangement in Chiral Solvents under High Pressure.

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Workup of the anal secretion of the mink by gas chromatography also gave 20 mg of a dark yellow, readily polymerizing
oil whose IR spectrum closely resembles that of ( 4 ) , except
for an additional band at 993 cm-I. This fraction was shown
to be 3,3-dimethyl-I ,2-dithiolane ( 5 ) , mainly by mass spectrometric analysis, and in particular by the base peak at m/e=69
(M - 65). The isomeric 4,4-dimethyl derivative could be ruled
out by comparing the UV spectrum of ( 5 ) with those of
five other dithiolanes.
We have investigated the rearrangement of racemic 1-(4methoxypheny1)-I -methyl-2;2-diphenyloxirane
(I ) in L-( +)diethyl tartrate at atmospheric pressure and at lo4 bar. After
hydrolysis of the L-( +)-tartrate, the main product 2-(4-methOCH,
+
In addition to ( 4 ) and ( 5 ) we also isolated a compound
(retention time 14min at 243°C) having a mercaptane type
odor, which we deduced to be diisopentyl disulfide (6) from
its mass spectrum. Finally, we isolated a hydrocarbon CloHzo,
which was not further characterized, and indole.
The malodorous substances of the weasel ( M . erminea L.)
and of the polecat ( M . putorius L.) were compared with those
of the mink by gas chromatography. Indole and the hydrocarbon C l o H z o were found in the weasel, and also ( 4 ) , . ( 5 ) ,
and (6) in the polecat.
Received: January 14, 1976 [Z 385 IE]
German version: Angew. Chem. 88. 228 (1976)
CAS Registry numbers:
13J. 31462-45-0: 14). 55022-72-5: ( 5 ) . 58384-57-9: 16J. 2051-04-9
( 7 ) . 58375-01-2
[ I ] I . Wilz, Dissertation, Universitat Heidelberg 1967.
[2] H . Schildknechr in F . Korte: Methodicum Chimicum. Vol. I, Part 1.
Thieme, Stuttgart 1973. p. 524.
[3] N . Cnrnd, Dissertation, Universitit Heidelberg 1972.
[4] M . L . Ziegler, J . Weiss, H . Srhildknecht, N . Grund, and H . E. Sasse,
Justus Liebigs Ann. Chem. 1973, 1702.
[ 5 ] C. Maver. Helv. Chim. Acta 57, 2514 (1974).
Enantioselective Wagner-Meerwein Rearrangement in
Chiral Solvents under High Pressure[**]
By Hans Plieninger and H . P. Kraemer[*l
Dedicated to Professor Karl Freudenberg on the occasion of
his 90th birthday
Only a few enantioselective reactions are known to take
place in a chiral medium without the latter entering into
reaction“]. The object of our study was to establish whether
enantioselective syntheses can be induced in a chiral medium
by employing high pressures.
We based our investigations on the known fact that reactions
in which at least partial charges occur in the transition state
have a strongly negative activation volume under high pressure
(cu. I O4 bar)12]. This “electrostriction” is due to increased
interaction of the solvent molecules with the partially charged
atoms of the molecules participating in the transition state.
Use of a chiral solvent and a starting molecule having a
prochiral functional group should give rise to two diastereomeric transition states under high pressure whose different
energy content must be due only to interaction with the solvent
and thus be a function of the pressure.
~~~
~
~~
[*] Prof Dr H. Plieninger and Dip1 -Chem H P Kraemer
[**I
Organisch-Chemisches lnstitut der Universitat
Im Neuenheimer Feld, 6900 Heidelberg 1 (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft.
Angew. Chem. Inr. Ed. Engl. I Wd. 15 ( 1 9 7 6 ) N o . 4
(3)
oxyphenyl)-2-phenylpropiophenone( 2 ) could be easily separated chromatographically from any 2-(4-methoxyphenyl)-3phenylindene (3) formed as by-product. The structures of
( 2 ) and (3) were confirmed by elemental analyses and ‘HNMR and IR spectra. The ratio of ( 2 ) to (3) is shifted
strongly in favor of ( 3 ) by pressure. Compound (2) (57 %)
obtained under high pressure (lo4bar) proved to be optically
active; [m]f:,=
- 1.1” (c=3.5; CHC13). The same reaction
carried out at atmospheric pressure, however, affords optically
inactive ( 2 ) (85 %). In order to confirm that the optical activity
was not due to the optically active solvent, the compound
( 2 ) obtained at high pressure was recrystallized several times
from different solvents (2 x ethanol, 2 x ligroin).
To determine the degree of asymmetric induction we prepared both enantiomers of ( 2 ) in optically pure form from
racemic 4-(cl-~hlorobenzyl)anisole ( 4 ) [(2) could not be
resolved]. Compound (5) (see Scheme) was separated by
column chromatography into the diastereomers (5 a ) and
(5 b ) , which on treatment with oxalyl chloride and diphenylcadmium furnished the enantiomers ( 2 a ) [[a]::,= + 16.24
(c=1.52, CHCI,)] and ( 2 b ) [[a]::,=
-16.10 (c=0.43,
CHCI,)], respectively.
9
Ph-C-Phi
A,
KCN
CHjCN
-Ph-C-Phi
[18]crown-6
-
I
I KNHz/NH,
Ph-
kN
2 CHd
(4J
1. KOH/
Diethylene sl>iol
2 . HCIIHZO
YH3
Ph-y-Ph’
COOH
1. NaH
2. CI-CO-CO-~CI
3. (+)d-Phenyl-
*
ethylamme
Ph’
Ph
I
I
Ph-C-C-NH-C-CH,
I It
I
H,C 0
H
Ph’
1 . CI- c o - C G C I
2. PhlCd
*
I
Ph-C-C-Ph
I 1
I
H,C 0
The asymmetric induction found in L-( +)-tartrate at high
pressure corresponds to an optical yield of p = 6.7 %. Highly
optically active ( 2 ) is likewise formed in other chiral solvents,
e. 9. menthol or fenchone, but its purity still has to be checked.
243
can be isolated only if both sides of the ring bear bulky
substituents.
To our knowledge this constitutes the first enantioselective
synthesis effected by pressure in a chiral medium.
Received: January 15, 1976 [Z 386 IE]
German version: Angew. Chem. 88,230 (1976)
Table 2. Physical properties of compounds (5)-(8).
were recorded in CC14 [a].
CAS Registry numbers:
5 ;.,j ., ,<!-j$2.5 4 Q, <.~.$?.? ., :
!3$2.5d.?$; $ ,'-.&., ,CS$Z.5 j .Sd .: $ ?,$,&., :
QZ.5 2 +7?;
13). 58375-20-5: ( 4 ) . 58375-21-6: ( 5 a ) . 58375-22-7: lSh). 58375-23-8:
oxalyl chloride. 79-37-8 : diphenylcadmium. 2674-04-6
.
[l] F. D. Saeua, P . E . Sharpe, and G . R. O h , J. Am. Chem. SOC. 97, 204
(1975); L. Verbit, 7: R. Halbert, and R . B. Petterson, J. Org. Chem.
40, 1649 (1975); D. Seebach and Hok A n Oei, Angew. Chem. 87, 629
(1975); Angew. Chem. Int. Ed. Engl. 14, 634 (1975).
[2] W J . I e Nohlr. P r o g Phys. Or@.Chem. 5. 207 (1967)
1-Cyclopropene-1-carboxylatesfrom 1-Chloro-1-cyclopropanecarboxylic A c i d s [ * * ]
The isolation of a 1-cyclopropene-I -carboxylic acid has
so far been accomplished in only one special case by lithiation
and carboxylation of 1,3,3-trimethyl-l-cyclopropene['l.
Attempts to obtain such acids by basic HBr-elimination[21
or thermal cleavage of acetic acidr3]from cyclopropanecarboxylic acids have failed.
We have now synthesized the l-cyclopropene-l-carboxylates ( 5 ) and (6) by removal of HC1 from the l-chloro-l-cyclopropanecarboxylates (3 b ) and (4 b ) with potassium tertbutoxide in THF. Few by-products are formed. We have
already prepared other cyclopropene derivatives in this
The esters (1 b ) - ( 4 b ) were obtained from the carboxylic
acids ( I a ) - ( 4 a ) by reaction with isobutylene. The acids
themselves are readily accessible from the 1,l-dichlorocyclopropanes by halogen-metal exchange and carboxylation (Table
1).
(1) - (4)
( a ) , 1t3 = H
( b ) , R 3 = tBu
1
AOOtBu
( J J , R = CH3
(61, R = Ph
cootBu
(7), R = H
(8), R = CHj
Table 1 . Synthesized acids ( I a ) - ( 4 a ) , R 3 = H , and esters ( I b ) - ( 4 b ) ,
R3=tBu. The 'H-NMR and mass spectra are consistent with the given
structures.
R'
(1)
(2)
(3)
(4)
H
H
CH3
Ph
RZ
H
CH3
CH3
Ph
(a)
M.p. r C ]
&F l . . d f . ~ q - , ~ ~ ~ ~ , ! . ~ 5 ~ 1 ~ ~~.-~~f.->HA,!R~ S _ P . ~ ~ ~ , ; 7 ..fRt5,,
1695cm-I; UV: 291nm (heptane); MS: no M', M f - C 4 H a 188 (44%),
M i-C4H, 187 (84%). M' -COzC4H, 143 (100%): high resolution: Mi C4H9 187.0743, calc. 187.0749
(6): M.p. 110°C. 'H-NMR: 6 = 1 59 (s. 9 H). 7.5 (mc. 15 H): IR: 1820. 1690
c m - l : UV.289 nm (heptane): MS (high resolution): M + 368.1773 (7%). calc.
368.1775; M t - C 4 H a 312.1105 (23 %), Mt-C02C4H9 267.1148 (100%)
(7): Colorless oil; 'H-NMR: 6=1.03 (s, 9H), 1.07 (s, 9H), 1.4 (mc, 1 H),
1.9 (mc, 2H), 7.2 (mc, SH); IR: 1730cm-'; MS: no M + , M + - C 4 H a 234
(8%), M + - 2 C 4 H a 178(100%)
(8): Colorless oil; 'H-NMR: 6=0.68 (d, J = 6 S H z , 3H), 0.97 (s, 9H), 1.49
(s, 9H), 1.90, 2.00 (AB system, B part as q, J = 7 + 6 . 5 H z , 2H), 7.35 (mc,
SH); IR: 1730cm-'; MS: no M t , M + - 2 C 4 H s 192 (59%), 105 (70%),
87(100%)
96
147
151
190
In elimination experiments with potassium tert-butoxide
( 1 b ) and ( 2 b ) gave, in addition to polymers, only the adducts
(7) and ( 8 ) , respectively, in 25-30% yield. Even with the
sterically more demanding potassium 3-ethyl-3-pentanolate
(1) afforded small amounts of (7) along with large amounts
of polymer. The configuration of ( 8 ) follows from attack by
the butoxide ion from the unhindered side and from the
coupling constants for trans cyclopropane protons.
tert-Butyl 2,3,3-triphenyl-l-cyclopropene-I-carboxylate
(6)
1,l -Dichloro-2,2,3-triphenylcyclopropane(10 mmol) in a
mixture of THF, ether, and petroleum ether ( 4 : l :Iv/v; 50 ml)
is treated dropwise under pure N, at - 105"C with butyllithium
(10mmol) in hexane, and then with an excess of pulverized
CO,. After usual workup, the valeric acid that is always
present is distilled off at 5O0C/O.0l torr and the residue crystallized from ether/petroleum ether; yield 55 % (4a).-A solution of ( 4 a ) (10mmol) in dry ether (10ml) is heated at 50°C
for 16h under N2 in a bomb-tube with ca. l o g isobutylene
and 0.2 g conc. H2SO4. After usual workup the crude ( 4 b )
is chromatographed on silica gel with pet. ether/ether (9:l);
yield 62 %.-A solution of potassium tert-butoxide ( 2 mmol)
in T H F (5ml) is added dropwise to an ice-cooled solution
of ( 4 b ) (2 mmol) in T H F (5 ml) (reagents purified according
to Ref. [4]) under purified N2. The mixture is stirred for
30min at 0°C and then for a further 30min at room temperature. After addition of 50ml CC14 the mixture is washed
twice with NH4Cl solution, three times with ice-water, dried
over MgS04 and finally concentrated by evaporation. The
crude ester (6) is recrystallized once from CCl4; yield 71 %.
fb)
M.p. ["C]
B.p. ["C/torr]
46
60/0.05
80/0.02
141
As expected the 1-cyclopropene-1-carboxylicesters ( 5 ) and
(6) (Table 2) are unusually strong Michael acceptors which
______
[*] Prof. Dr. P. Weyerstahl and Dipl.-Chem. V. Sander
lnstitut f i r Organische Chemie der Technischen Universitat
Strasse des 17. Juni 135, 1000 Berlin 12 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie.
244
( 5 .1;. njl:.,'H:Nh/lR;.
[a] (8) in CDC13 (WH-270).
By Volker Sunder and Peter Weyerstahl"]
ci' ' C O O R ~
All NMR spectra
Received: December 29, 1975 [Z 394 IE]
German version: Angew. Chem. 88, 259 (1976)
CAS Registry numbers:
( I a ) , 58486-07-0; ( I b ) , 58486-08-1 ; ( Z a ) , 58486-09-2; ( Z b ) , 58486-10-5;
f 3 a ) . 58486-11-6; ( 3 b ) , 58486-12-7: ( 4 a ) . 58486-13-8: ( 4 h ) . 58486-14-9;
( 5 ) . 58486-15-0: ( 6 ) . 58486-16-1 : (7), 58486-17-2: (8). 58486-18-3: 1.1-dichloro-2.2.3-triphenylcyclopropane.33027-37-1
G . L. Closs and L. E. Closs, J. Am. Chem. SOC.83, 1003 (1961); 85,
99 (1963); I . B. Arezoo, I . G . Bolezoo, and R. Ya. Leoina, Zh. Org.
Khim. (Engl. translation) 1975, 2129.
121 K . B. Wiberg. R. K . Barnes, and J . Albin, J. Am. Chem. SOC. 79, 4994
(1957).
[3] K . B. Wiberg and R. K . Barnes, J. Org. Chem. 23, 299 (1958).
[4] K-0. Henseling and P . Weyerstahl, Chem. Ber. 108, 2803 (1975).
[I]
Angew. Chem. Int. Ed. Engl. / Vol. 15 (1976) No. 4
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