вход по аккаунту


Stabilization of the Unstable Tautomers of Phosphino- and Arsino-Substituted Ylides by Coordination to Transition Metals.

код для вставкиСкачать
Stabilization of the Unstable Tautomers of
Phosphino- and Arsino-Substituted Ylides by
Coordination to Transition Metals**
By Lothar Weber*, Roland Boese, and Wolfgang Meyer
Of the phosphino- and arsino-substituted ylides of type
1 , the tautomers 1A and 1B can be formulated, whereby
the equilibrium for X = H at room temperature lies completely on the side of lA['I.
E = P, A s ; X = H , s u b s t i t u e n t s capable of mesomerism
R = Alkyl, A r y l
Substituents X that are capable of mesomerism favor the
tautomer l B , which can b e fixed as complex ligandl'l. We
have now been able to stabilize the tautomer l B , also
when X = H, by coordination to transition metals. On reaction of the sulfur-ylide complexes 2[91or 6["] with the methylenebisphosphanes 4a-4c and methylenebisarsane 4d
the unstable ylide tautomer is fixed as ligand to the transition metal. Formally, the (CO),CrCH, building block in 2
or 6 is transferred to 4a-4d in a substitution reaction.
The 3'P-NMR spectra (200 MHz, 25"C, CDC13, ext.
H,PO,) of the yellow, briefly air-stable complexes 5a-5c
prove the presence of two different types of phosphorus
atoms (5a: 6=43.78 (d), 65.47 (d), J=84 Hz; 5b:
J * ~ = 8 1Hz; 5 ~6 ~
: 9 0 . 5 8(d), 155.75
(d), J = 105 Hz). In 5d, the methylene protons give rise to
two singlets, in 5a-5c, on the other hand, to two doublets
of doublets. The X-ray structure analysis of 5d (Fig. 1) con-
firms the presence of a five-membered metallacycle in envelope conformation (dihedral angle 36.7 ").
The free ylide ligands of the complexes 5c and 5d were
hitherto completely unknown. The method described here
is thus a general route to complexes with unstable ylide ligands of the type 1B.
Received: July 26, 1982 [Z 107 IE]
Supplemented: October 4, 1982
German version: Anqew. Chem. 94 (1982) 938
The complete manuscript of this communication appears in:
Anqew. Chem. Suppl. 1982. 1934-1942
[I] H. Schmidbaur, A. Wohlleben-Hammer, Chem. Ber. I12 (1979) 510: M.
S. Hussain, H. Schmidbaur, Z . Natuforsch. B 31 (1976) 721 ; H. Schmidbaur, W. Tronich, Chem. Ber. 101 (1968) 3545: K. Issleib, H. P. Abicht,
J. Prakt. Chem. 312 (1970) 456: K. Issleib, R. Lindner, Justus Liebiqs
Ann. Chem. 699 (1966) 40: 707 (1967) 120.
[2] N. Holy, U. Deschler, H. Schmidbaur, Chem. Ber. 115 (1982) 1379; H.
Schmidbaur, U. Deschler, Chem. Ber. 114 (1981) 2491.
[9] L. Weber, J. Orqanomet. Chem. 105 (1976) C9.
[I I ] L. Weber, Z . Natuforsch. 831 (1976) 780.
112) a) H. H. Karsch, H. Schmidbaur, Z . Naturforsch. 8 3 2 (1977) 762: b) Z.
S. Novikova, A. A. Prishchenko, 1. F. Lutsenko, Zh. Obshch. Khim. 47
(1977) 775.
Synthesis of an Octasaccharide
of the Basic Sequence of N-Glycoproteins**
By Hans Padsen* and R o y Lebuhn
Fig. 1. Structure of the complex 5d in the crystal. Monoclinic space group
C2/c: a=2194.2(7), b = 1418.5(4), c=2753.7(9) pm: p= 138.87(2)';
V=5.638(3)x lo9 pm'; Z = 8 , R=O.O35.-Some selected bond lengths [pml
245.0(1), As(])-C(5)
197.1(5), C(5)-As(2)
and angles ["I: Cr-As(1)
191.4(7), As(2)-C(6)
188.8(4), C(6)-Cr
222.1(6): CrAs( I)C(5) 109.8(2),
As( l)C(5)As(2) 106.3(2), C(5)As(2)C(6) 107.6(3), As(2)C(6)Cr I13.6(2),
C(6)CrAs(l) 88.1(1). Further details of the crystal structure investigation can
b e obtained on request from the Fachinformationszentrum Energie Physik
Mathematik, D-75 14 Eggenstein-Leopoldshafen 2 (Germany), quoting CSD
50289, name of author, and full citation of Journal.
W. Meyer
Institut fur Anorganische Chemie der Universitat
Universitatsstrasse 5-7, D-4300 Essen 1 (Germany)
[**I Transition Metal-Sulfur Ylide Complexes, Part 17. This work was supported by the Fonds der Chemischen Industrk-Part 16: L. Weber, D.
Wewers, Chem. Ber.. in press.
The oligosaccharide chain 9 is a basic sequence present
as a building block in numerous N-glycoproteins['], and is
bonded at the reducing end to L-asparagine via a glucosamine moiety. Both lactosamine antennae having the nonreducing end groups are usually occupied by N-acetylneuraminic acids"].
Until recently, the B-D-( I -4)-mannoside bond to the
glucosamine in 9 could not be synthesized directly. Using
a silver silicate
we recently were able to prepare
saccharides 2 and 6I3], which were required as educts for
the oligosaccharides 5 and 9.
Trisaccharide 3, which is obtained from 2 (Scheme l),
can be selectively coupled with the lactosamine bromide
l I 4 I in presence of silver trifluoromethanesulfonate (Ag-triflate, collidine, - 40 "C) to afford the pentasaccharide 4
(75%, [a]? -9.7, c = 1.2 in CHC13) with the desired p-Dglycosidic linkage. 4 could be deblocked as follows:
Firstly it is deallylated (70%) with PdCI,/AcOH/NaOAc.
Deacetylation, hydrazine cleavage of the phthalimido
group, acetylation, and subsequent hydrogenolytic cleavage of the benzyl groups, as well as reacetylation led to a to-
[*] Priv.-Doz. Dr. L. Weber, Dr. R. Boese,
0 Verlag Chemie GmbH, 6940 Weinheim. 1982
R. Lebuhn
lnstitut fur Organische Chemie und Biochemie der Universitlt
Martin-Luther-King-Platz 6, D-2000 Hamburg 13 (Germany)
Oligosaccharide Building Blocks, Part 42.-Part 41: H. Paulsen, M.
Paal, Carboh-vdr. Res.. in press.
[*] Prof. Dr. H. Paulsen.
0570-0833/82/1212-0926 $ 02.50/0
Angew. Chem. lnt. Ed. Enql. 21 (1982) No. I2
Без категории
Размер файла
118 Кб
tautomeric, metali, coordination, unstable, arsine, transitional, substituted, phosphine, ylide, stabilization
Пожаловаться на содержимое документа