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Isothiocyanato Carboxylic Acids and 2-Thioxo-5-oxazolidones.

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B-l'-B-&B-5
and its chemical equivalent in the asymmetric
unit of the molecule. Likewise, the B-H-B
bonds are not
characteristic open three-center bonds. I n such a case the
bonding electrons are supposed to be concentrated on the
lines connecting the atoms B-H-B.
Fig. 3 clearly shows that
this is not so.
Received: April 8, 1970
[ Z 212 IE]
German version: Angew. Chem. 82, 519 (1970)
[*I Prof. Dr. R. Brill, Dr. H . Dietrich, and Dr. H. Dierks
Fritz-Haber-Institut der Max-Planck-Gesellschaft
1 Berlin 33, Faradayweg 4-6 (Germany)
[ l ] J . S . Kasper, C. M . Lucht, and D . Harker, Acta crystallogr.
3, 436 (1950).
[2] M. Dettke, Dissertation, Technische Universitat Berlin
1966.
[ 3 ] A. Tippe and W . C. Hamilton, Inorg. Chem. 8, 464 (1969).
[4] H . Dietrich, Messtechnik 76, 303 (1968).
[5] H . Dietrich and H . Dierks, Messtechnik 78 (1970), in press.
161 Internat. Tab. X-Ray Crystallogr., Vol. 3, 202. Kynoch
Press, Birmingham 1962.
[7] R. &if/, Zeitschrift Elektrochem. 63, 1088 (1959); Acta
Crystallogr. 13, 275 (1960).
[S] W. N . Lipscomb: Boron Hydrides. W. A. Benjamin, New
York 1963.
Isothiocyanato Carboxylic Acids and
2-Thioxo-5-oxazolidones
By Hans R . Kricheldorfr*]
Isothiocyanato carboxyIic acids ( 3 ) and 2-thioxo-5-oxazolidones ( 4 ) can be polymerized with loss of COS to give polyamides or peptides.
The hitherto unknown trimethylsilyl isothiocyanato carboxylates (2), which proved accessible by silylation of N-dithiocarboxy amino acid derivatives ( I ) , appeared suitable as
starting materials for the preparation of (3) and ( 4 ) (R1 :=
C O - O C Z H ~ ~ ~C2H5[21,
],
C H Z - C ~ H[31;
~ for R and n, see
Table).
S
-
I1
2(CH,)3SiCII2N(CzHs),
4
- - - z N ( ~ ~ ~ ~ ~ ~HCI
.
t
R'-S-C-NH-(CHR)n-COOH
14)
m.p.( "C)
-
C
d
e
f
g
[a]
1
H
CH3
CH*CH(CH&
CHzC6Hs
H
H
H
U
b
D,L
form.
67-7011
52-55/10-2 [a]
75-78110-3 [b]
122--125/10-3 [bl
1
1
1
2
3
81-84/1
5
95-98/10-3
70-73/10-*
-
-
70-72
93-95
-
10-12
18-20
32-34
[b] L form.
(2) + C,H,OH
I
SCN-(CHR), - C 0 2 H
+
TT:
s o
(41
526
All the new compounds listed were characterized by C, H, N
elemental analysis and IR spectra, and some of them by
N M R spectra.
Isocyanato carboxylic acids (3) and 2-thioxo-5-oxazolidones(4)
Triethylamine (2.1 moles) is added dropwise to a warm
mixture of ( I ) (1 mole), having R1 = CO-OCzH5, CzH5, or
C H ~ - C G H ~ ,and trimethylchlorosilane (2 moles) in dry
toluene (ca. 1.5 I) and the reaction mixture is heated to
boiling for 2 h. Precipitated triethylammonium chloride is
filtered off and the esters ( 2 ) are isolated in 7 6 9 0 % yield by
fractional dist i I lat ion.
A solution of ( 2 ) (0.1 mole) in light petroIeum (10&150 ml)
is treated at 0 ° C with dry ethanol 10.1 mole) and a catalytic
amount of dry hydrogen halide, and the solution is stirred at
0"Cuntil theproduct [ ( 3 )or ( 4 ) ] hasprecipitated(5-30min).
The 2-thioxo-5-oxazolidones (4) must be filtered off, dried in
a high vacuum, and used immediately. At 20 "C compound
(46) yields a solid foam of poly-D,L-alanine within about
20 min of isolation.
Received: April 21, 1970; revised: May 8, 1970 I
2 220 IE]
German version: Angew. Chern. 82, 550 (1970)
[*] Dr. H . R. Kricheldorf
Institut fur makromolekulare Chemie der Universitat
78 Freiburg, Stefan-Meier-Strasse 31 (Germany)
[I] T . Higashimura, H . Karo, K . Suzuoki, and S . Okamura,
Makromolekulare Chem. 90, 243 (1966).
121 A . Fredga, Svensk kem. Tidskr. 5 4 , 2 6 (1942); Chem. Abstr.
40, 2797 (1946).
[3] Ch. E . Dalgliesh, J. chem. SOC.(London) 1949, 2373.
[4] A. D . Grabenko, V . V . Stophan, M . N . Danchenko, T . I .
Cherepenko, and P. S . Pel'kis, Fiziol. Aktiv. Veshehestva, Akad.
Nauk Ukr. SSR, Repub. Mezhvedom. Sb. 1966, 104; Chem.
Abstr. 67, 3037 (1967).
[5] The p-, y-, and c-isothiocyanato carboxylic acids and
their silyl esters have an extremely powerful urticating action
and give rise to painful blisters and wounds, even in high
dilution.
Cycloadditions of Vinylcarbenes
By Michel Franck-Neumann and Chrisriane Buchecker * I
The carboxylic acids (3) can be liberated in 85-95 % yield
from the silyl esters (2) by treatment with ethanol at 0 "C.
C,H,0Si(CH3),
The cc-compounds ( 2 a ) to ( 2 d ) gave only the 2-thioxo-5oxazolidones ( 4 ) . These compounds have a low thermal
stability; for example, (4a) and (4b) decompose within a few
hours at room temperature, and, although slower, also at
temperatures as Iow as about -20 "C. Those bearing larger
substituents, e.g., ( 4 c ) and ( 4 d ) , exhibit a definite melting
point and can be kept at -20 "C for several weeks. Decomposition involves loss of COS to give peptides; a concurrent
isomerization gives the morestable thiazolidin-2,5-diones, but
in far smaller yield.
,!3-Isothiocyanatopropionicacid (3e) also polymerizes in the
course of a week at +25 "C to give oligo-P-alanine. In contrast, y-isothiocyanatobutyric acid (3f)and E-isothiocyanatohexanoic acid ( 3 g ) (which has already been prepared by
another rnethodr41) are stable at room temperature. The
compounds polymerize readily only above about 150 "C or,
in the presence of triethylamine (not pyridine!), above 50 "C.
Copolymers can be isolated from mixtures of monomers [51.
(31, n>,2
Carbenes that can undergo intramolecular stabilization
generally react very reluctantly with other molecules [I]. This
appears to be the case, for example, with vinylcarbenes which
can give cyclopropenes by intramolecular addition [2,31 and
which, to our knowledge, exhibit no intermolecular additions
providing proof of carbenoid structure 141.
We have now been able to intercept the vinylcarbenes supposed to give rise to cyclopropenes via diazoalkenesc31 on
photolysis of 5-cyano-3H-pyrazoles 151. This was accomplished by intermolecular cycloaddition to alkenes, alkynes,
and dienes to give vinylcyclopropanes, vinylcyclopropenes,
and divinylcyclopropanes, respectively.
Angew. Chem. internat. Edit.
I Vol. 9 (1970) I N o . 7
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acid, thioxo, carboxylic, oxazolidonen, isothiocyanate
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