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Dicyclopentadienyleuropium.

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genes faecalis, which utilize (4) and ( 5 ) as sources of
nitrogen and carbon, deaminate these substances to the
respective lumazine derivatives, which then undergo
oxidation to 2,4,6,7-pteridinetetraone (163). The isomerization of (163) t o xanthine-8-carboxylic acid (164)
is achieved enzymatically.
6-methyl- or 6,7-dimethyl-5,6,7,8-tetrahydropterin
[319]
or by tetrahydrobiopterin indicates that a 6-substituted
tetrahydropterin is involved. The partially hydrogenated
pteridine derivative [320] produced in the course of the
hydroxylation is neither a 5,8- nor a 7,8- nor most
probably a 5,6-dihydropterin. Hence, it is likely that an
oxidation-reduction system is involved. This system may
have compounds (165) and (166) as components.
VII. The Biochemical Role of Unconjugated
Pteridines
By his study of the enzymatic hydroxylation of phenylalanine to form tyrosine, Kuufmun [317] has made a
valuable contribution t o the knowledge of the biochemistry of the pteridines [316]. H e was able to show
[317,318] that two enzymes are involved in the overall
reaction
H+
+ TPNH + 0 2
phenylalanine + TPN- i- HlO
- tyrosine
(where TI" = triphosphopyridine nucleotide and
T P N H = reduced TPN). One of the enzymes, isolated
from rat liver, catalyses the hydroxylation; it contains a
tetrahydrogenated, unconjugated pteridine as a cofactor. The second enzyme, obtained from sheep liver,
acts in conjunction with T P N H to induce rehydrogenation of the dihydropteridine to the tetrahydro stage.
Details of the structure of the cofactor are still unknown.
The fact that the cofactor can be replaced by either
[316] S. Kaufman [141.
[317] S. Knufman, J . biol. Chemistry 226, 5 1 I (1957).
[318] S. Kaufman, J . biol. Chemistry 230, 931 (1958).
This first example in which a simple unconjugated
pteridine plays the role of a cofactor can be considered
to be the beginning of a new chapter in the development
of pteridine chemistry. It does not seem improbable
that other biological functions of the pteridines will be
discovered in the near future.
Received, March IIth, 1963
[ A 335/134 IE]
German version: Angew. Chem. 75, 993 (1963)
[319] S. Kaufman, J. biol. Chemistry 234, 2577, 2683 (1953).
[320] S. Kanfman, J. biol. Chemistry 236, 801 (1961).
COMMUNICATIONS
Formyl Chloride
By Prof. Dr. H. A. Staab and Dipl.-Chem. A. P. Datta
Organisch-chemisches Institut der Universitat
Heidelberg (Germany)
When dry HCI is passed into a solution of an imidazolide (11
i n chloroform or methylene chloride, an acid chloride is obtained as a result of acqlation of the hydrogen chloride. Although the transacylation reaction (a) is reversible, as is shown
by the formation of imidazolides from acid chlorides and
imidazole, the acid chlorides are formed in practically quantitative yield, since imidazolium chloride formed in a subsequent reaction precipitates out. Acid chlorides whose synthesis hy the usual methods is attended by difficulties can be
prepared by this route, since imidazolides are readily accessible from carboxylic acids and I, 1'-carbonyldiimidazole.
of (1) obtained as filtrate was stable for one hour at -60 "C.
After addition of methanol, methyl formate was isolated
in 65-70 % yield. At -40 OC, we obtained only 9 "/, ester
under otherwise identical conditions. The thermal decomposition of ( I ) into CO and HCI, which is still being investigated quantitatively, was also followed by direct determination of the carbon monoxide evolved.
Received, August 16th. 1963: publication withheld until now at the
[ Z 563/445 IEI
request or the authors.
German version: Ansew. Chem. 75, 1203 (1963)
~
~~
[I] See H . A . Stanb, Angew. Chem. 74,407 (1962); Angew. Chem.
internat. Edit. I, 351 (1962).
[ 2 ] N. A . Staab and B. Polenski, Liebigs Ann. Chem. 655, 95
( I 962).
Dicyclopent adienyleuropium
By Prof. Dr. E. 0. Fischer and Dipl.-Chem. H. Fischer
lnstitut fur Anorganische Chemie der Universitat Miinchen
(Germany)
The long sought for formyl chloride (/) has now been
obtained on a preparative scale for the first time. We passed
HCI into a solution of I-formylimidazolr, [2] in CHC13
at -6O'C and filtered off the quantitative precipitate of
imidazolium chloride formed in the cold through a sintered
glass filter in a closed apparatus. The chloroform solution
132
Treatment of the blue solution of metallic europium in liquid
ammonia with cyclopentadiene in a ratio of 1 : 3.1, thermal
degradation of the yellow reaction residue at 200 OC in vacuo,
and rapid heating to 420-440 "C affords yellow dicyclopentadienyleuropium in 20 %, yield in the form of a crystalline
sublimate. This is the first "sandwich" compound prepared
Angew. Chem. internut. Edit.
1 Vol. 3 (1964) 1 No. 2
Characterization and Stabilization of
Dithiobenzil by Complex Formation
which contains a divalent lanthanide. The complex is formed
in accordance with the equation
By Priv.-Doz. Dr. G. N. Schrauzer and H. W. Finck
I t is soluble in liquid ammonia and in dimethylformamide, is
extremely sensitive to air and moisture, and has a magnetic
moment of 7.62 B. M. [l]. Its paramagnetism is thus practically equal t o that anticipated for the Eu2+ ion (7.9 B. M.).
The salt-like character of the complex,which must be assumed
o n the basis of this observation, is only slightly affected by
covalent centric 0-bonding contributions, as is shown by the
position of the ycH-frequency at 739 cm-1 in the infrared
spectrum. The presence of symmetrical five-membered rings
follows from the vcH-band at 3077 cm-1, the wcc-band at
1435 cm-1, and the 8cH-absorption at 1007 cm-1. The simiand the comlarity between TEuZ+ = 1.09 and rSr2+ = 1.10
parable bond character are reflected in the agreement between
the corresponding frequencies of Sr(CsH5)z [21 (739, 3077,
1435, and 1008 cm-1) and of Eu(CgH&.
a,
Institut fur Anorganische Chemie
der Universitlt Miinchen (Germany)
According to Mitru [I], three compounds are formed in the
reaction between benzoin and H2S in ethanolic HCI, viz.
( I ) , m.p. 195 OC, (2), m.p. 126 "C, and ( 3 ) , m.p. 97 "C. As
this author regarded (3) as monomeric dithiobenzil, we felt
it desirable to check his claims, particularly since we were
interested in (3) as a possible starting material for a new
synthesis of bis(dithiobenzi1)nickel ( 4 ) . which can also
be obtained, for example, from nickel sulfide and tolane [2].
Although we were able to confirm Mitra's results, a revision of the structures he suggests is necessary. In agreement with R . Muyer and Nitzschke [3], we found that (1) is
tetraphenyldithiacyclohexadiene and that (2) is 5-ethoxy2,3,5,6-tetraphenyl-1,4-dithiacyclohexene;however, we also
Received, November 22nd, 1963 [ Z 621/452 IE]
German version: Angew. Chem. 76, 52 (1964)
~
[ I ] According to investigations of K . E. Schwarzhans.
121 E . 0.Fischer and G . Stofzfe,Chem. Ber. 94, 2107 (1961).
Hydrothermal Sintering
By Prof. Dr. R. Brill and I. Melczynski
Fritz-Haber-Institut der Max-Planck-Gesellschaft,
Berlin (Germany)
Various methods for thermal sintering of metal powders are
known. A similar effect may be obtained with some metal
powders by treating them with water. This effect was discovered accidentally, when we tried to wash iron carbonyl
powder with water in a Soxhlet apparatus. After extraction
for several hours, the metal powder had formed a firmly
cohering cake. We found that the iron particles always cake
together if they are placed in close contact with one another
and then treated with warm water or boiled with water. The
hydrothermally sintered solids are strong enough to be turned
o n a lathe; the exposed surface acquires the typical appearance of iron. The surface may also be polished to a high gloss,
but under the microscope the polished surface exhibits a
grained structure. There are some particles with a strong, metallic lustre besides some weakly reflecting ones ond some
dark, void spaces. The X-ray diagram shows not only the
lines for cc-iron, but also those of iron spinel. On heating with
water, the surface of the iron particles has therefore evidently
reacted with the water, yielding the anhydrous spinel phase
Fe304 as the effective product which firmly cements the individual iron particles together.
Closely similar effects have been observed with aluminum
and zinc, starting with commercial A l and Zn powders. X-Ray
studies showed that the metal particles are joined together by
Bohmite and ZnO respectively.
It is interesting that the caking of the above metal powder
particles produces structures that have enough mechanical
strength for considerable amounts of other metals, which d o
not sinter hydrothermally on their own, or even of inert substances to be embedded in the cake. The mechanical strength
of hydrothermally sintered solids does not appear to be high
enough for engineering purposes. During their preparation
they may, however, be easily combined with non-metals such
as paper and plastics.
We do not intend to continue studies o n hydrothermal sintering effects from either the scientific or the commercial point
of view.
Received, November 25th, 1963 [Z 622/450 IE]
German version: Angew. Chem. 76, 52 (1964)
Angew. Chem. internat. Edit./ Vol. 3 (1964) / N o . 2
P h = CsH,
succeeded in isolating ( 3 ) (softening point 1O5-11O0C,
yield: 3 based on benzoin) in solid, analytically pure, but
non-crystalline form [4]. Molecular-weight determinations
show that Mitm's dithiobenzil is actually tetrameric. In the
proton magnetic resonance spectrum only signals of the
phenyl protons were detectable. Therefore, a cyclic structure
with S-ASbonds could be present. When heated, ( 3 ) decomposes into sulfur and tetraphenylthiophene. On treatment with N ~ ( C O ) ~ . ~ P ( C ~inH Sxylene,
)~
( 3 ) gives the
nickel complex (4) in good yield. The same complex is
formed when benzoin is reacted with H2S under the above
conditions in the presence of NiC12 (yield 10% based on
benzoin). In this reaction, the unstable precursor of (31,
dithiobenzoin, is trapped by the added metal salt.
Received, November 25th, 1963 [ Z 632/460 IE]
German version: Angew. Chem. 76, 143 (1964)
-.
~~
[ I ] S . K . Milra, J. Indian chem. SOC. 15, 5 8 (1938).
[2] C. N . Schrairzer and V . Mayweg, J. Amer. chem. SOC.84,
3221 (1962); Z. Naturforsch. Ser. b, in the press.
131 R . Mayer and M. Nitzschke, Chem. Ber. 96,2539 (1963).
[4] Compound ( 3 ) forms minute, pale yellow, transparent
globules.
1,2- and 1,4-Hydrostannationof Conjugated Dienes
By Priv.-Doz. Dr. W. P. Neumann and
Dip1.-Chem. R. Sommer
Chemisches lnstitut der Universitat GieDen (German))
Hydrostannation of a-olefins [ I ] proceeds by way of radicals
[la, 21. Therefore, i t seemed worthwhile to examine the
behavior of conjugated dienes in this reaction. Butadiene,
substituted butadienes (2), and cyclopentadiene are readily
hydrostannated by a radical mechanism at 60-80 "C.
Radical scavengers inhibit, radical-producing agents accelerate the reaction. The main product is the 1,4-adduct
133
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