close

Вход

Забыли?

вход по аккаунту

?

Enantioselective Synthesis and Thermal Reorganization of an Optically Active Methyleneaziridine.

код для вставкиСкачать
coordinated pseudohalide complex of boron linked via
nitrogen.
When tetraphenylphosphonium difluorooxosulfimidate
(I )C31 (0.44g, 1.O mmol) and boron tris(difluorooxosu1fimidate)
(,?)["I (2g, 6.4 mmol) are condensed together in a glass trap
at -80°C and the product mixture is allowed to warm to
room temperature over 12h, stirred for a further 5 to 6 h
and the excess of (2) removed by pumping (48h), ( 3 ) is
obtained in quantitative yield as a white crystalline solid
whose X-ray diagram differs from that of ( I ) and whose
elemental analysis proves it to be pure ( 3 ) . The 'H-NMR
spectrum is compatible with that of ( I ) and of (C6H5),PC1;
the 19F-NMR spectrum shows a singlet at 6= -51.8 (in acetonitrile, rel. CFC13 ext.). Together with the IR spectrum
(3028 w, 1590 m, 1450 vs, 1342 w, 1320 w, 1260 s, 1192
m, 1113 s, 1003 m, 940 vs, 785 vs, 756 m, 728 vs, 695 s,
590 m, 560 m and 530 s cm-'; KBr pellet) the "BfNMR
spectrum, in particular, with a signal at 6=7.96 (in [D3]-acetonitrile, rel. BF3. OEt2 ext.), provides evidence for the tetracoordination of the boron. This experimental value corresponds to that expected according to a Scheme described by
Noth and Vahrenkamp for the chemical shift as a function
of the electronegativity of the ligand atoms X in BX? compIexe~[~].
Received: January 30, 1978 [Z 915 IE]
German version: Angew. Chem. 90, 226 (1978)
CAS Registry numbers:
( I ), 14872-92-5; ( 2 ) , 38998-35-5; ( 3 ) , 65749-23-7
~-
[l] E . Wiberg, H. Michaud, 2. Naturforsch. B9, 499 (1954).
[2] F . Klanbrrg, 2. Anorg. Allg. Chem. 316, 197 (1962).
[3] H. W Roesky, 0.Glemser, A. HOE W Koch, Inorg. Nucl. Chem. Lett.
3, 39 (1967).
[4] Ch. Jackh, A . Roland, W Sundermeyer, Z. Naturforsch. B27, 1102 (1972).
[5] H. Norh, H. Vahrenkamp. Chem. Ber. 99, 1049 (1966).
Enantioselective Synthesis and Thermal Reorganization
of an Optically Active MethyleneaziridineC**]
By Helmut Quast and Carlos A . Weise Ve'lez"]
The routine application of conclusions reached for hydrocarbons to the corresponding hetero systems can be inadmissible in the case of strongly perturbed pericyclic reactions['].
While the thermal isomerization of methylenecyclopropanes is
known to be largely stereospecific with inversion at the migrating carbon atom['], nothing is known about the stereochemistry of the thermal reorganization of heteromethylenecyclopropanes apart from the racemization of optically active 2,3-ditert-butylcycl~propanone[~"~
and the rearrangement of optically active allene oxide intermediates[3b1.We have now found
that the methyleneaziridine-cyclopropanimine
rearrangement'"] also proceeds stereospecifically.
The optically active methyleneaziridine (-)-(2) could be
synthesized in 36-48% yield by lithiation of (1)[51 using
1.08 equivalents of sec-butyllithium in pentane at - 125°C in
[*I Prof. Dr. H. Quast, Dr. C. A. Weise VBlez
Institut fur Organische Chemie der Universitat
Am Hubland, D-8700 Wiirzburg (Germany)
[*'I This work was supported by the Deutsche Forschungsgemeinschaft.
The results are taken from the dissertation by C . A. Weise Wlez, Universitat
Wurzburg 1977.
Angew. Chem. I n / . Ed. Engl. 17 ( 1 978) N o . 3
the presence of 9.10 equivalents of (S,S)-(+)-1,4-bis(dimethylamino)-2,3-dimethoxybutane [( + )-DDB] as auxiliary chiral
agentL6]and subsequent reaction with 1.05 equivalents of
chloro(trimethy1)silane at - 125 to - 20°C. Enantioselective
metalations have hitherto rarely been observed['!
b.
c H~
1. sBuLi/(+)- DDB,
pentane, - 125 "C
+
2. (CH&SiCL,
- 1 2 5 to-20°C
( C H3 )3Si
c H3
After repeated fractional distillation in a 20-cm Spaltrohr@column (b.p. 52.5 "(775 torrf, (-)-(2) proved to have a
purity of 98% (GC) and a specific rotation of [a]$& = - 86.27"
([( - )-(2)] = 0.348 mol/l in [D6]-benzene). Integration of the
trimethylsilyl 'H-NMR signals in benzene using P r ( f a ~ a m ) ~ [ ~ I
as shift reagent revealed an enantiomer excess of 12.4f 1%.
Solutions of (2) in [D6]-benzene were heated in sealed
NMR sample tubes previously treated with 0,N-bis(trimethy1sily1)acetamide and degassed at
torr. In the case of
racemic (2) the thermolysis was monitored 'H-NMR spectroscopically on a single sample by measurement of the trimethylsilyl signals, while in the case of (-)-(2) nine identical samples
were firstly measured 'H-NMR spectroscopically and then
polarimetrically at 405 nm under strict exclusion of moisture.
At 120.0"C thermolysis of (2) afforded the diastereomeric
methyleneaziridines ( 3 ) and cyclopropanimines ( 4 ) in the
constant isomeric ratios ( E ) - ( 3 ) : ( Z ) - ( 3=
) 86: 14 and ( E ) - ( 4 ) :
(2)-(4)
= 56:44, respectively. Decomposition of ( 4 ) into methyl isocyanide and trimethylsilylethene["] was not observed at
120°C but only at 140°C and above, albeit to a small extent.
However, at 120°C unknown secondary products of ( 4 ) were
very slowly formed (trimethylsilyl singlets at 6" =0.05, 0.1 I ,
0.29), which after 24 h only amounted to 6-10 % of the total
product mixture and were added to ( 4 ) in the kinetic
evaluation.
The structures of (2) and its rearrangement products
( 3 ) and ( 4 ) follow from the IR and 'H-NMR spectra (Table
1). IR (C, cm-') (2): 1790, 1760 (gas phase); ( 3 ) : 1735, ( 4 ) :
1773 (both in C6D6). 'H-NMR (C6D6; ZiH) ( E ) - ( 4 ) : -0.08
((CH3)&); ( Z ) - ( 4 ) : - 0.02 ((CH3)3Si).Both diastereomeric
cyclopropanimines ( 4 ) show overlapping multiplets at 6~ =
0.3-1.5 and 3.2-3.3 belonging to two ABCX3 systems. In the
case of ( 3 ) the configuration was determined on the basis
of the ally1 coupling constants, while in the case of ( 4 ) the
predominant diastereomer was assigned the (E)-configuration.
Noteworthy is the coupling constant of "5=0.4 Hz between
3-H and the N-methyl group of (2) which, with this order
of magnitude, is obviously observable only if the trans invertomer predominates.
Owing to the irreversibility of the rearrangement to cyclopropanimine~[~]
and the constant E : Z ratios in the case of
both ( 3 ) and ( 4 ) , four rate constants were sufficient for the
description of the thermal reorganization of (2). Starting
Scheme 1:
from approximate values, obtained from initial data of the
thermolysis of (2) and of a 5 : 9 5 mixture of (2) and ( 3 ) , by
213
Table 1. 'H-NMR data for the methyleneaziridines in [D6]-benzene.
Chemical shifts 6H
3-R'
4-R2
Cpd.
NCHs
3-H
Coupling constants IJI [Hz]
4-R3
2J
4J,,s
4Jtrms
( I i [h]
141
1.885
(21
2.39 [c]
0.95
(E)-(3)
2.26
1.75
(Z)-(3)
2.32
1.64
(CHsMi
0.07
H
4.559
H
4.54
(CH3)3Si
0.16
H
4.975
H
4.579
H
4.66
H
4.980
(CHaLSi
0.22
[a]
5Jt,.ns
~-
~~~
1.15
0.XS
1.32
< 0.1
1.11
1.35
1.90
ca. 0.1
-
-
1.1
-
-
0.7
-
ca. 0.1
[a] Estimated from the broadening of the signals of R2= H and the N-methyl groups.
[b] In CC14; the data of the ABX2 system were optimized using the program LAOCOON I11 [9].
[C] 4 J ( 3 . ~ , ~ . c ~ 3 ) =
HZ.
o.4
means of a program developed for the computation and drawing of mol fraction-time curves based on the solutions of the
differential equations corresponding to Scheme I[''',
we obtained the optimized constants listed in Table 2.
Table 2. Rate constants of the thermal reorganization of methyleneaziridine
( 2 ) according to Scheme 1 in [D6]benzene at 120.0"c.
Rate constants x lo5 [s']
k32
k24
Thermolysis of
k23
k34
~~
racemic ( 2 ) [a]
(-)-f2) P I
6.20
5.90
0.36
0.37
2.80
3.60
0.165
(0.02)
[a] One sample consisting of 0.063 ml of (2) in 0.520ml of [D6]benzene
0.010 benzene.
[b] Nine identical samples; [(-)-(,?)I =0.348 mOl/l.
+
Table 2 shows satisfactory agreement between the data
obtained in different ways. The trimethylsilyl group at the
double bond stabilizes ( 3 ) by 9.2 kJ/mol compared to (2).
From the rate constants it can be estimated that initially very
little (4) is formed (after 10h only 4%, total 30-35%) via
achiral (3) and that only negligible racemization of (-)-(2)
occurs in this way.
In the thermolysis of (-)-(2) the mol fractions x(i) after
10h were: x(2)=0.06, x(3)=0.56, x(4)=0.35 and x(secondary products of ( 4 ) ) = 0.03. But a405 had only decreased from
ao= -4.330" to -2.03'
b a t h length= 10cml. (4), and
thus also the optically active species, was selectively and completely removed without altering any of the other components
(IR and 'H-NMR spectra) by treating a sample of (-)-(2)
[x(4) =0.35, a405 = - 1.720'1, previously heated for 22.6 h,
with water. Consequently, only (4) was optically active and,
like the educt (-)-(2), levorotatory ; however, the enantiomer
excess of ( - ) - ( 4 ) could not be determined. Assuming that no
direct racernizati~n[~"'
of (-)-(2) takes place, the maximum
possible contribution to a405 arising from (-)-(2) can be
calculated according to q2,
= aoexp- (kZ3 k 2 4 ) t . Thus, for
( - ) - ( 4 ) a minimum rotation of a(4,=(a-q2,)/~(4)=
-5.5950.15" (from 5 measurements during the first 5 h,
[( - ) - ( 4 ) ] =0.348 mol/l in ED6]-benzene)is obtained, which is
considerably greater than the initial value a0 and therefore
indicative of a high degree of stereospecificity for the methyleneaziridine-cyclopropanimine rearrangement. Since on geometrical grounds retention at the migrating carbon atom,
C-3 in ( 2 ) , is highly improbable, inversion must have
occurred as in methylenecyclopropanes[zl.
+
Received: Bnuary 16, 1978 [Z 913 IE]
German version: Angew. Chem. 90, 224 (1978)
CAS Registry numbers:
(I), 25012-55-9; (-)-(2), 65665-40-9; (*)-(2), 65665-41-0; ( E ) - ( 3 ) , 6566542-1; (Z)-f3),65665-43-2; (E)-( - ) - ( 4 ) , 65665-44-3; (Z)-(- ) - ( 4 ) , 65665-45-4;
(+)-BDB, 26549-21-3
214
[l] 8. Schilling, J . P . Snyder, J. Am. Chem. SOC.97, 4422 (1975); E Jean,
A. Devaquet, ibid. 99, 1949 (1977); D. H . Hunter, S. K . Sim, R . P.
Steiner, Can. J. Chem. 55, 1229 (1977).
[ 2 ] W uon E. Doering, L. Birladeanu, Tetrahedron 29, 499 (1973); J . J .
Gajewski, S. K . Chou, J. Am. Chem. SOC.99, 5696 (1977); references
cited therein.
[3] a) D. B. Scloue, J. F . Pazos, R . L . Camp, F . D. Greene, J. Am. Chem.
SOC.92, 7488 (1970); b) M. Bertrand, J . P . Dulcere, G . Gil, Tetrahedron
Lett. 1977, 4403.
[4] H . Quast, W Rider, Angew. Chem. 85, 411 (1973); Angew. Chem.
Int. Ed. Engl. 12, 414 (1973).
[5] H . Quast, C . A . Weise Vklez, Angew. Chem. 86, 380 (1974); Angew.
Chem. Int. Ed. Engl. 13, 342 (1974).
161 D. Seebach, H . - 0 . Kalinowski, B. Bastani, G. Crass, H. Daum, H . Dorr,
N . P. DuPreez, 1.: Ehrig, K Langer, C . Niissler, H.-A. Oei, M . Schmidt,
Helv. Chim. Acta 60, 301 (1977).
[7] D. Seebach, K . - H . Geiss, J. Organomet. Chem. Libr. 1, 58 (1976); E
Izumi, A. Tai: Stereo-differentiating Reactions. Academic Press, New
York 1977, p. 115.
[S] H . L. Goering, J . N. Eikenberry, G . S. Koermer, C . J . Lattimer, J.
Am. Chem. SOC.96, 1493 (1974).
[9] W Rider, Dissertation, Universitat Wurzburg 1977.
[lo] The solutions quoted by E. S . Lewis and M. D. Johnson, J. Am. Chern.
SOC.82,5399 (1960), contain errors. We thank Dipl.-Math. S . Stindl and
DipLChem. M. Heuschmann for correcting these and Dr. W Rider for
writing the computer program.
Difluoroarsoranes and Homologous Compounds
R'R2EF2(E= As, Sb, Bi) by Oxidative Direct Fluorination of Organoarsanes, Organostibanes, and Organobismuthanes[**]
By Ingo Ruppert and Volker Bastian"]
Selective gas phase fluorinations of organoelement compounds are comparatively rarely exploited reactions in preparative chemistry[']. The observed oxidative fluorination of the
phosphorus in tertiary phosphanes['] without significant formation of side-products has now been extended for the first
time to its higher homologs.
Ph2E-R
+
Fz
ma3
(1)
E = A s : R = Me(a), Ph(b);
E = S b : R = Mefc), Phfd);
F
I
PhZE-R
I
F
(2)
E = B i : R = Ph(e)
[*] Dr. I. Ruppert ['I, Dr. V. Bastian
Anorganisch-chemisches Institut der Universitat
Gerhard-Domagk-Str. 1, D-5300 Bonn 1 (Germany)
[+]Author to whom correspondence should be addressed.
['*I Fluorinated Organoelements: Oxidative Liquid-Phase Direct Fluorination, Part 3.-Part 2 : I . Ruppert, Chem. Ber., in press.
Angew. Chem. Int. Ed. Engl. 17 (1978) No. 3
Документ
Категория
Без категории
Просмотров
0
Размер файла
232 Кб
Теги
reorganization, synthesis, thermal, optically, methyleneaziridine, activ, enantioselectivity
1/--страниц
Пожаловаться на содержимое документа