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Isomerizations of Alkenylidenecyclopropanes Catalyzed by Lewis Acids.

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Procedure:
Hexamethyldisilazane (25g) is added dropwise to a stirred
solution of 1,2,3,5-tetramethyl-4,6-di~hloroborazine[~~
(1 2.8g)
in dry toluene with exclusion of moisture. After refluxing
for 3 h and removal of toluene by distillation the residue
is refluxed with a further portion (100 ml) of hexamethyldisilaZane for another 2.5h. The colorless residue obtained on
distillation of the hexamethyldisilazane is subjected to molecular distillation
torr) and yields a small amount of (2)
at 120°C bath temperature and ( 3 ) at 150°C. O n heating
to more that 500°C in an air bath compound ( I ) sublimes
over.
>=GG?44
trans: ( 4 I
lUO% ( 9 )
\
+
%
(10)
Received: January 16, 1975 [Z 183 IE]
German version: Angew. Chem. 87, 382 (1975)
CAS Registry numbers:
( I ) . 54750-92-4: (2). 54750-93-5: (3). 54750-94-6;
1.2.3.5-tetramethyl-4,6-dichloroborazine.7387-21-5 :
hexamethyldisilazane. 999-97-3
[ l ] Cf. H . Steinherg and R . J. Brotherton: Organoboron Chemistry, Vol. 2.
Wiley-Interscience, New York 1966.
[2] M. F . Lappert and M . K . Majumdar, Proc. Chem. SOC. London 1963. 88.
131 A. Stock and E. Pohland. Chem. Ber. 59,2215 (1926).
[4] H . S. Turner and R. J. Warne, Proc. Chem. SOC.London 1962.69.
[ 5 ] A. Meller and M . Wechsherg, Monatsh. Chem. 98, 513 (1967).
[6] R. J. Wagner and J . C. Bradford. Inorg. Chem. 1.93 (1962); R. H . Tornniskoetter and F . R . Half, ibid. 2. 29 (1963).
bly attributable to direct opening of the C2-C3 bond of
( 5 ) with subsequent allenylmethyl-butadienyl rearrangement
and [1,4]-hydride shift["].
Remarkably, it is always the carbon atom displaying the
lowest degree of substitution (C3)which undergoes alkyl shift
and 1,3-elimination in all the cited isomerizations. This leads
to clear-cut reaction courses in all cases.
[1,2]-AIkyl
Isomerizationsof AlkenylidenecyclopropanesCatalyzed
by Lewis Acids
,
(312%
By Lutz Fitjer"]
Cyclopropyl and cyclopropylmetbyl cations are usually
generated in the presence of a nucleophile which is incorporated into the final product[''. However, they should also be
accessible in the form of the complexes ( I ) and (2) in the
absence of nucleophiles by reaction of suitably substituted
methylenecyclopropanes with Lewis acids and thus permit
pure isomerizations during cyclopropyl-ally1 or cyclopropylmethyl-cyclobutyl rearrangements. This is indeed the case.
p@
(2)
L60
Treatment of 2-methyl(2-methyl-l -propenylidene)cyclopropane ( 3 ) [ and trans-2,3-dirnethyl(2-methyl-l
-propenylidene)cyclopropane (4)['l with boiling ethereal zinc iodide solution['] affords 3-isopropylidene- 1-methyl-1 -cyclobutene (8)[61
and 3-isopropylidene-1 ,4-dimethyl-l-cyclobutene(9)I3I, respectively, each as the sole reaction product. In contrast, 2,2dimethyl(2-methyl-1-propenylidene)cyclopropane (6)IZ1 and
2,2,3-trimethy1(2-methyl-1-propenylidene)cyclopropane ( 7)"'
underwent quantitative isomerization to diisopropylidenecyclopropane ( I / ) ['I and 1,2-diisopropylidene-3-methylcyclopropane (/2)['l. cis-2,3-Dimethyl(2-methyl-l-propenylidene)cyclopropane (5)IZ1gave a mixture of ( 9 ) and 3-ethylidene-5methyl-l,4-hexadiene (/0)[31.
As shown for the case of ( 3 ) , the isomerizations of (3)-(5)
can only be explained in terms of complex formation via
C' and subsequent [1,2]-alkyl and [1,2]-hydride
In
contrast, the isomerizations of ( 6 ) and (7) must be preceded
by complex formation via C". In this case cyclopropyl-ally1
rearrangement and trans-1,3-elimination lead to formation
of ( 2 1 ) and ( I 2 ) , respectively. Formation of (10) is presuma[*I Dr. L. Fitjer
Organisch-Chemisches Institut der Universitat
34 Gottingen, Tammannstrasse 2 (Germany)
360
The above examples demonstrate that cyclopropyl, cyclopropylmethyl (or 1-cyclopropylvinyl), and possibly also
allenylmethyl cations are accessible by complex formation
of suitably substituted alkenylidenecyclopropaneswith Lewis
acids, the nature of the cations formed being crucially dependent upon the substitution pattern of the cyclopropane ring.
Received: January 15, 1975 [Z 187 IE]
German version: Angew. Chem. 87, 381 (1975)
CAS Registry numbers:
(31, 54724-63-9; (41, 37817-46-2; (5). 37817-36-0; (6). 28438-32-6;
171. 14803-30-6; (81. 10412-56-3: (91, 54677-56-4: 1/01, 54677-57-5;
3761-85-1 ; 1/21. 13303-32-7: Znl,. 10139-47-6
~
C. D. Gutsche and D. Redmore, Advan. Alicyclic Chem. Suppl. 1, p.
1 ( 1 968).
(31 C31, (41 [4a], (5) [la]. f61 [4b, 4c], and (7) [4c, 4d] were
prepared according to Crandall [4d] by reaction of 1-bromo-3-methyl1,2-butadiene with potassium tert-butoxide in an excess of the corresponding alkenes.
The new compounds ( 3 ) . (9). and ( 1 0 ) gave correct analytical values;
IR. UV, MS data accord with the structures given. The configuration
of (10) was not determined. 'H-NMR data (100MHq CCI,, TMS
int.): (3): 6=0.93 (m. LH), 1.16 (d, CH3, J = 6 H z ) , 1.47 (m, 2H),
1.68 (s, 2 C H 3 ) ; (9): 6=1.07 (d, CHI, J = 7 H z ) , 1.55 (br. s, 2 C H d
1.77(br. s. CH,), 2.88 (br. q. 1 H, J = 7 Hz). 5.95 (9, =CH--, J = 1.5 Hz);
(10): 6=1.47 (d. CH,, J = 1 . 5 Hz), 1.59 (d, CH,. J = 7 . 5 Hz), 1.81 (d,
CH,, J = 2.0 Hz), 4.80 (br. d, 1 H, J = 10 Hz), 4.89 (br. d, 1 H, J = 17 Hz),
5.50 (br. q, l H , J=7.5Hz), 5.53 (br. s, lH), 6.20 (dd, l H , J = 1 0 and
17 Hz).
a) H. D. Hartzler, J. Amer. Chem. SOC. 83, 4997 (1961); b) ibid. 83,
4990 (1961); c) G. Leandri and C. Santelfi-Rourirr. Bull. SOC. Chim.
Angew. Chem. internat. Edit.
1 Vol. 14 ( 1 9 7 5 ) 1 No. 5
[5]
[6]
[7]
[8]
[9]
[lo]
Fr. 1970, 1515; d ) D. R. Paulson, J . K. Crandall. and C. A. Bunell.
J. Org. Chem. 35, 3708 (1970).
Isomerization was performed by refluxing solutions of ( 3 j - ( 7 )
(5mmol) in 2.0M (12.51111) ethereal zinc iodide solution for 2-4 h.
The isomerizations can also be carried out on a preparative scale:
l 0 m l of 3.5 M ethereal zinc iodide solution isomerized u p t o 70mmol
(6).
(8) was hitherto only accessible by quaternization of l-aminomethyl-3isopropylidenecyclobutane and subsequent Hofmann degradation (J.
K. Williams and W H. Sharkey, J. Amer. Chem. SOC.81, 4269 (1959)).
(11 j can also be prepared by reaction of l,l-dibromo-2-methyl-l-propene with methyllithium in the presence of 3-methyl-1.2-butadiene (R.
F. Bleiholder and H. Shechrer, J. Amer. Chem. SOC. 86, 5032 (1964)).
( 1 2 j is also obtained alongside isomeric dialkylidenecyclopropanes
on thermal isomerization of ( 7 ) [4d].
Compare the results obtained on solvolysis of substituted l-cyclopropylvinyl cations (D.R. Kelsey and R. G. Bergmann, J.C.S. Chem. Comm.
1973. 589).
Alternatively, consecutive [1,3]- and [1,2]-hydride shifts are also conceivable; specific deuteration of ( 5 ) should clarify this matter.
Facile Synthesis of ~-3(3,4Dihydroxyphenyl)alanine
( L - D o ~and
) Related Compounds
By E.-0. Renth"]
Dedicated to Professor Karl Zeile on the occasion of his 70th
birthday
Use of L-dopa ( 3 b ) in the treatment of Parkinson's disease
prompted us to search for a simple and inexpensive synthesis
of this compound. The synthesized L-dopa must be free from
the D-enantiomer, which leads to clinical side effects.
Our process consists in enzyme-induced (e.g. by papain)
asymmetric synthesis. Substituted DL-N-benzoylphenylalanine derivatives are transformed into the optically active
L-amino acid anilides ( 2 ) , which are then hydrolyzed to give
the L-amino acids ( 3 ) .
solution of about 3 g of papain in 0.05 N citrate buffer (300 ml)
is then added and the pH adjusted to 5.80 by addition of
glacial acetic acid or 1 N sodium hydroxide solution. After
a short time the ~-anilide( 2 a ) begins to precipitate; after
48 h it is filtered off under suction, washed with water (300ml),
and dried; m. p. 208-209 "C.
~-3-(3,4-Dihydroxyphenyl)alamne(L-dopa) ( 3 b )
L- N-Benzoyl-3-(3-hydroxy-4-methoxyphenyl)alany~ani~ide
( 2 c ) (9.75g, 25 mmol) is refluxed for 7 h with 48% hydrobromic acid (50ml). After cooling, benzoic acid is filtered off
and rinsed with a small volume of cold 48% hydrobromic
acid, and the slightly yellow solution evaporated down in
uacuo. The residue is dissolved in methanol (50ml) and propylene oxide (5ml) is added. The temperature is maintained
at 50°C until the pH value of 6.0 has been attained, and
the mixture is then cooled and the product ( 3 6 ) is filtered
off under suction and recrystallized from water.
~-N-Benzoyl-3-(4-hydroxy-3-methoxyphenyl)alanine
(3a) and
-3-(3-hydroxy-4-methoxyphenyl)alanine( 3 c )
The L-anilide ( 2 a ) or ( 2 c ) is refluxed for 16 h in the tenfold
amount of 2~ HCI. The reaction mixture is then cooled and
repeatedly extracted with ether. The aqueous phase is filtered
over charcoal and vacuum distilled. The residue is dissolved
in a fivefold amount of ethanol. Propylene oxide is added
and the temperature maintained at 50°C for 1h until the
pH value 6.0 is attained. The solution is allowed to stand
for ca. 12 h in a refrigerator, filtered under suction, and (3a)
or ( 3 c ) recr!\callized from water; the monohydrate is
obtained.
Received: February 6, 1975 [Z 199 IE]
German version: Angew. Chem. 87.379 (1975)
CAS Registry numbers:
(10). 2901-78-2; ( 2 ~ ) 38152-95-3;
.
( 2 c ) , 50713-71-8;
( 3 a ) , 300-48-1 ; (3b). 59-92-7; f 3 c ) , 35296-56-1
Preparation and Reactivity of Sterically Crowded Porphyrins'"]
RID
F-
C F I Z - ~ : ~ COOH
R2
R1
R2
L-12 J
Yield
[%I
'[a]?,,
["I
L-(3 I
.
Yield
[%I
in C H 3 0 H
a
OCH,
OH
b
OH
OH
c
OH
OCH3
100
95
-!-40.0
c= 1
+41.8
~
I
[a]!& ["I
in 1 N HCI
68
- 5.83
c= 1
69
-12.15
c=4
61
- 8.5
c=2
c = 0.5
~-N-Benzoyl-3-(4-hydroxy-3-methoxypheny[e
f2a)
DL- N-Benzoyl-3-(4-hydroxy-3-methoxyphenyl)alanine
(la)
(31.5g, 0.1mol) is dissolved with warming in 0 . 0 5 ~sodium
hydroxide solution (200ml). After addition of 2~ sodium
acetate solution (150ml) the mixture is filtered. 0 . 0 5 ~citrate
buffer (pH 5.0,300ml), cysteinium chloride (2g), and distilled
aniline (18 ml) are then added successively to the filtrate. A
[*] Dr. E.-0. Renth
C. H. Boehringer Sohn, Abteilung Pharmachemie
6507 Ingelheim (Germany)
By Ludger Witte and Jiirgen-Hinrich Fuhrhop"]
Recent biochemical concepts on the activation of oxygen
by heme enzymes". 21 and the photolysis of water by chlorophyll dimersL31should be amenable to checking with synthetic
metalloporphyrins in uitro. Simple analogs of these important
redox catalysts would be of interest from the preparative
standpoint both for the oxygenation of olefins as well as
for the hydroxylation of non-activated hydrocarbons. For
the synthesis of rigid ligand fields about the central iron
atom in heme analogs or of dimers having porphyrin planes
at a well-defined distance, we require porphyrins containing
the same side chains, which are capable of being coupled
with each other, at oppositely lying methine bridges (u,y).
From these it should be possible, e.g., to prepare stericaily
fixed ansa porphyrins having rigid axial ligands through the
central ion. To our knowledge, porphyrins with highly substituted methine bridges were previously only accessible by lengthy total synthesis14! We now wish to report on their prepara[*] Dip1.-Chem. L. Witte and Doz. Dr. J.-H. Fuhrhop
Gesellschaft fur Molekularbiologische Forschung mbH
3301 Stockheim bei Braunschweig, Mascheroder Weg 1
and
Institut f i r Organische Chemie A der Technischen Universitat
Braunschweig (Germany)
[**I This work was supported by the Bundesministerium f i r Forschung und
Technologie as part of the technology program, by the Deutsche Forschungsgemeinschaft and by the Fonds der Chemischen Industrie.
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acid, isomerization, alkenylidenecyclopropanes, lewis, catalyzed
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