close

Вход

Забыли?

вход по аккаунту

?

Synthesis of Trisubstituted Olefins via Trimethylsilylated Phosphorus Ylides.

код для вставкиСкачать
Starting from the diaminodiphosphanes 1 and 21Za1we
have now succeeded in synthesizing the tetraphosphabicyclobutane system (4a, b) by PP-coupling to give the tetraphosphane 3 and subsequent cyclizing amine-elimination.
H
H C1
RzN-P-P-NRZ
H H
+ RZN-P-P-NRZ-
2
1
P4
+ [RZN-Pl4-
> 15ooc
R~N-P-P-NR,
I
Base
R~N-P-P-NRz
3
-Ease'
H
R2r;r
5
R = SiMe,
P
P
4a, b are pyrophoric, thermally remarkably stable compounds, of which 4b is obtained in pure form from the
isomeric mixture by crystallization. Its composition is confirmed by correct elemental analysis and by the mass spectrum (field ionization, M + =444.1).
The "P('H]-NMR spectrum of 4a, b (30% in CD2C12,
H3P04 ext.) shows the resonance absorptions of the bridgehead atoms, as expected, at very high field [6= -222.5
(4a), -287.3 (4b)l. The signal pattern for the resonance
absorptions of the peripheral phosphorus atoms, shifted
about 200 ppm downfield, affords proof of the cis,transk242, k255 Hz,
form for 4a (S= -19.7, -43.4, 'Jpp=
2Jpp=
f31.5 Hz) and is consistent with a CZvsymmetry[31
for 4b (S= -79.1, 'Jpp=225 Hz), where model considerations support the sterically favored trans,trans-arrangement. This could be confirmed by a complete X-ray structure analysis (Fig. 1).
The P-P bond lengths of the peripheral phosphorus
atoms being 2.22-2.23 A correspond to a "normal" single
bond. A surprising feature, however, is the extremely short
A
bridgehead bond, which, with a value of 2.13 (P4: 2.21
A) indicates considerable double bonding. According to
this "x-bonding" arises from an effective
charge transfer of the equatorially arranged bis(trimethy1sily1)amino groups (angle between the normals to the
planes Si2N and NPPN: 92") to the central P-P bond.
Also worthy of note is the transannular P-P distance of
only 2.81 I\ (bonding angle 95.2").
The instability to be expected for the tetraphosphabicyclobutane system B compared to a decomposition into A
and C manifests itself in the fragmentation into phosphorus and 5 above 1500C12a1.
Procedure
A mixture of 1 (0.005 mol), 2 (0.05 mol) and quinoline
(20 mL) was stirred for 24 h at 6O0C/1O torr under an inert
gas. Extraction of the reaction mixture with 100 mL of npentane furnished essentially only 3[41and unreacted 2 .
After removal of solvent from the extract, vacuum shortpath pyrolysis at 130- 135" U 0 . 5 torr afforded 8 g of the
crude product (4a, b) as a red, highly viscous oil, which
still contained ca. 5% of 2, 5 and P4. 4b could be isolated
in pure form as ebony colored needles (2.5 g e 11%) by recrystallization from a little n-pentane.
Received: March 19, 1982 [Z 152 IE]
German version: Angew. Chem. 94 (1982) 553
[I] C. Brown, R. F. Hudson, G. A. Wartew, Phosphorus Su[fur S (1978) 67,
and references cited therein.
[2] a) E. Niecke, R. Riiger, Z. Naturforsch.. in press; b) W. W. Schoeller, C.
Lerch, Inorg. Chem., in press.
[3] 'H- and "C{'HI-NMR spectra of 4b are likewise consistent with the Czv
symrnetry:6'H=0.3; 6I3C=4.2 (q), 13JJpc+4JpcI=4.8
Hz (30% in CD2CIz,
TMS int.).
141 "P-NMR: 6=76.5, 7.5, ' J ~ ~ = 2 1Hz
5 (preferred stereoisomer).
Synthesis of Trisubstituted Olefins
uiu Trimethylsilylated Phosphorus Ylides
By Hans Jurgen Bestmann* and Andreas Bomhard
Dedicated to Professor Klaus Weissermel on the occasion
of his 60th birthday
The synthesis of phosphorus ylides 6 with R ' + R 2 (R',
R2 H) causes problems, since the reaction of secondary
alkyl halides with triphenylphosphane to afford phosphonium salts also leads to elimination. Secondary reactions afford a mixture of isomeric phosphonium salts,
which can only be separated with difficulty. The alkylation
of ylides 1 with alkyl halides 5 also produces mixtures"].
We have found that the pure ylides 6 can be synthesized
and immediately converted oia the following route: reaction of 1 and 2 (molar ratio 2 : 1) yields, via transylidation[lal,the salt 4 and the silylated ylides 3[2.31,which react
with the halogen compounds 5 to afford the phosphonium
(with tesalts 713].Desilylation of 7 with cesium
tra-n-butylammonium fluoride yields are, in general, poor)
results in formation of the disubstituted ylides 6, Addition
of aldehydes 8 (best in dimethylformamide) after the desilylation leads to trisubstituted olefins 9 via a Wittig reacti~n'~].
Wittig reactions with ylides such as 6d and 6i (see Table
l), which can hardly be prepared from the corresponding
+
P
co'
N
21
.?
57.1
p0
0
Fig. 1. Top: Molecular structure of 4b in the crystal; bottom: most important
bond lengths and angles (5 <0.005 and 0.04", respectively). 4b crystallizes
monoclinically, space group P2,/c, a = 11.872(2), b = 18.058(3), c = 12.259(2)
A,~=105.34(2)",p,=1.17gcm-3,Z=4(measured at -115°C). Thecrystal
structure was determined by direct methods (MULTAN) from 2933 singlecrystal diffractometer data and refined to R =0.065.
A
Angew. Chem. Int. Ed. Engl. 21 (1982) No. 7
(*] Prof. Dr. H. J. Bestmann. A. Bomhard
Institut fur Organische Chemie der Universitat Erlangen-Nurnberg
Henkestrasse 42, D-8520 Erlangen (Germany)
0 Verlag Chemie GmbH, 6940 Weinheim, 1982
OS70-0833/82/0707-0S4S $02.50'0
545
H
R
2
:@
1
phPO
1
+ CLSI(CH&
Si(CH3)3
R 1-C :0
2
I
-[R'CHn-?PhslCle
4 > Ph3P0
3
R3- CHO
l\
/3=CH-R3
8
Ra:
R2 9
@
C-PPh,
R i 6
C-
'SF
[
7i(CH3)3
R'-C-R2
X@
4Ph3 7]
droxy-2-( 1,2,4-triazol- I-y1)acrylic acid ester 4 is obtained
in good yields. 2 reacts with chlorotrimethylsilane to give
the trimethylsilyl enol ether 3, whose hydrolysis, which already occurs on removal of the sodium chloride formed in
presence of moist air, likewise gives 4, in quantitative
yield.
The 'H-NMR spectrum of the ester 4 in CDC13 and dimethyl sulfoxide (DMSO) shows that only the enols are
present. In the case of 4 it was found by 'H-NMR and
Table I . Synthesized products 7 and 9 .
~
7
R'
R'
X
I
I
I
I
Br
I
I
I
Br
Yield
[%I
M.p. ["C]
(decomp.)
R'
Yield
~
~~~
9
9. p. ["C/torr]
E
. Z [a]
[%I
92
84
94
96
Ibl
[bl
88
93
91
61
46
83
45
15
35
52
42
55
661 12
108-112/16
78-81/1.0
90/0.05
102112
110/12
70-75/0.6
125/1.8
58 : 42
53 : 47
11 : 89
4 : 96
1 :99
[dl
57 : 43
23 : 77
80/0.05
[a] Determined by gas chromatography. [b] Reacted further without being characterized. [c] (CH3)2C=CH-(CHZ)I-C(CH3)=CH (8g =citral). [dl 4 isomers
(22 :39: 15 :24), not unambiguously assigned. [el CHz=CH--(CH2)8.
phosphonium salts because of simultaneous Hofmann degradation, can also be carried out in this way['"].
Our conceptions of the mechanism of the Wittig reactionlsbl d o not lead us to expect high stereoselectivity in the
formation of trisubstituted olefins 9 from 6 with substituents R' and R2 having similar steric and electronic structure. This is conformed by the results in Table I .
13
C-NMR spectroscopic investigations that only the 2form exists in DMSO, whereas both the 2- (ca. 88%)
Na, HCOOEt
Toluene
N-CHZ-COOEt
1
Received: March 12, 1982 [ Z 142 IE]
German version: Angew. Chern. 94 (1982) 562
[I] a) H. J. Bestmann, Angew. Cfiern. 77 (1965) 609,651, 850; Angew. Chern.
Int. Ed. Engl. 4 (1965) 583,645,830; b) H. J. Bestmann, H. Schulz, Chem.
Ber. 95 (1962) 2921.
[ 2 ] The reaction has already been described for R ' = H, and also the subsequent reaction with methyl iodide: D. Seyferth, G. Singh, J . Am. Cfiem.
Soc. 87 (1965) 4156; H. Schmidbaur, W. Tronkh, Chern. Ber. 100 (1967)
1032.
[3] 3: 2 (220 mmol) is added dropwise to a stirred solution of 1 (400 mmol)
in 1 L of benzene at room temperature. The mixture is refluxed for 40 h, 4
is filtered off, and the crystalline ylide 3 isolated by removing the solvent.-7: 5 (22 mmol) in 50 mL of ether is added dropwise to a stirred
solution of 3 (20 mmol) in 100 mL of ether at room temperature. At the
end of the reaction (decoloration) the salt 7 is filtered off and dried in vacuo.-9: A solution of 7 (20 mmol), and 8 (22 mmol) in 100 mL of anhydrous dimethylformamide is treated with CsF (22 mmol) and stirred for
1-2 d at room temperature. After hydrolysis with IS0 mL of water, the
mixture is extracted with pentane (3 x 50 mL). The extract is chromatographed on silica gel 60 using petroleum ether and subsequently distilled.
[4] For an analogous desilylation of 7, R ' =R'= H, cf. E. Vedejs, G. R. Martinez, J. Am. Chern. Sor. I01 (1979) 6452.
[ S ] a) H. J. Bestmann, H. Hgberlein, 1. Pils, Tetrahedron 20 (1964) 2079; b) H.
J. Bestmann, Pure Appl. Chern. 52 (1980) 771.
- NaCl
N=/
T'N-C-COOEt
11
CHONa
I
H20,
Ha
4
3
and the E-form (ca. 12%) are present in CDCl3 13J(H,
CO,,,,,) = 8 Hz, E-form; 3J(H,C0,,,) = 2 Hz, Z-form]. In
CDC13 the O H protons of the 2-form form hydrogen
bonds with N2 of the triazole moiety, and those of the Eform form such bonds with the oxygen of the carbonyl
group.
Table I. Synthesized compounds 6 (selection).
R
M.p. ["C]
R
M.p. ["C]
3-Hydroxy-2-(l,2,4-triazol-l-yl)acrylic Acid Ethyl
Ester and 0-Functional Derivatives
By Thomas Maier* and Friedrich Cavagna
Dedicated to Professor Klaus Weissermel on the occasion
of his 60th birthday
The triazolylacetic ester 1 can be formylated with ethyl
formate"]. O n acidifying the sodium enolate 2, the 3-hy[*I Dr. T. Maier, Dr. F. Cavagna
Hoechst Aktiengesellschaft
D-6230 Frankfurt am Main 80 (Germany)
546
0 Verlag Chemie GmbH, 6940 Weinheim. 1982
rn-C6HS-O-C6H4CH2 oil
Alkylation and acylation of the enolates 2 in dimethylformamide (DMF) take place only at the oxygen under the
0570-0833/82/0707-0546 $02.50/0
Angew. Chern. Inl. Ed. Engl. 21 (1982) No. 7
Документ
Категория
Без категории
Просмотров
2
Размер файла
207 Кб
Теги
synthesis, trimethylsilylated, olefin, ylide, trisubstituted, via, phosphorus
1/--страниц
Пожаловаться на содержимое документа