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Crystalline -Radicals Containing Lead Ц Isotropic 207Pb-ESR Hyperfine Structure.

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state. The Konigs-Knorr synthesis in the presence of silver
carbonate probably occurs analogously.
Received: February 26, 1970
[ Z 173 IE]
German version: Angew. Chem. 82, 480 (1970)
Publication delayed at authors' request
[*I Dr. G. Wulff, Dipl.-Chem. G. Rohle, and
Dip1.-Chem. W. Kriiger
Institut fur Organische Chemie und Biochemie
der Universitat
53 Bonn 1, Meckenheimer Allee 168 (Germany)
[**I Glycoside Synthesis, Part 1. - This work was supported
by the Deutsche Forschungsgemeinschaft.
[ l ] Extracts from the Habilitationsschrift by' G. WuZfl, Bonn,
1970.
[2] H. Lettre and A . Hagedorn, Hoppe-Seylers Z . physiol.
Chem. 242, 210 (1936).
131 C. Meysfre and K . Miescher, Helv. chim. Acta 27, 231
(1944).
[4] N . K . Kochetkov, A . J . Khorlin, and A . F. Bochkov, Tetrahedron 23, 693 (1967).
[ 5 ] After conclusion of this work, Professor B . Helferich informed us that he had obtained ethyl @-D-ghcoside from
2,3,4,6-tetra-o-acetyl-or-o-glucopyranosy~bromide and ethanol
in the presence of silver salts of dicarboxylic acids (unpublished
work).
Crystalline x-Radicals Containing Lead Isotropic 207Pb-ESRHyperfine Structure
By Hartinut B. Stegmann, Klaus Schefller, and
Fritz Stocker [*I
Dedicated to Professor Eugen Miiller on the occasion of his
65th birthday
Attempts to prepare solutions of paramagnetic organolead
compounds - in particular by dissociation of hexaaryldiplumbanes "1 - have so far been unsuccessful. We have now
been able to isolate lead-containing radicals as products of
the reaction of 2-amino-4,6-di-tert-butylphenoxyl
( I ) with
diaryllead dihalides. Reaction of the aminoaroxyl ( I ) with,
e.g., di-p-tolyllead dichloride in ethanol affords violet-brown
crystals, m.p. 143-145 "C. Elemental analysis and mass
spectrum suggest structure (2). While solid (Zb) gives an
intense ESR signal exhibiting exchange narrowing, its solution in benzene gives a multicomponent spectrum.
Em
Figure: ESR spectrum of the di-p-tolyllead radical (2b) in benzene at
room temperature.
The central section of the hyperfine structure (HFS) of this
spectrum (see Figure) can be interpreted in terms of magnetic
coupling of the free electron with two pairs of protons and
one 14N nucleus. The less intense components lying on the
left- and right-hand sides can be attributed to further coupling
with a z07Pb nucleus. This isotope (I = 1/2) has a n abundance
of 22.62% in natural lead. The observed spectrum agrees very
well with this figure, as is shown by the successful simulation
(CDC 3300) of a n enlarged spectrum.
The isotopic spectrum is masked by the main spectrum only
in the central region, which corresponds to the 77.38% of
456
nonmagnetic lead nuclei present; thus if both groups of satellites are taken into consideration, the whole 207Pb HFS can
be observed. Exact measurements show that the distances
between the satellite centers and the center of gravity of the
whole spectrum differ in the upfield and downfield directions.
This asymmetry is attributable to a second order shift such
as has already been detected quantitatively for radicals
containing tin [21.
In agreement with other findings, the ESR spectra show the
new organolead derivatives to be 11,ll-disubstituted 1,3,7,9tetra-tert-butyldibenzo[d,g]- [1,3,6,2]dioxazaplumbocin-5-yls.
The coupling parameters were initially assigned by analogy
with the corresponding tin compounds 121.
ESR data for the radicals (2) (gauss), recorded in benzene at room temperature;
A H = line width.
(a). R
=
C&
(bj, R
=
p-CH3-C6H4
1 1 1 1 1 1
1.62
3.24
7.05
41.68
2.00081
0.76
1.62
3.12
7.14
40.54
2.00093
0.70
As expected, the substituent R has only a limited effect on
the coupling constants. The exceptional line broadening
(% 0.7 gauss) is probably due either to an unresolved proton
HFS o r to unfavorable relaxation conditions. Since the
spectra remain essentially unchanged between -70 and
+120°C, the line broadening cannot be due to mechanical
movement. The g factors of compounds (2a) and (26) are
remarkably small, owing to interaction of the free electron
and the P b nuclei which has also been determined from the
HFS spectra.
Received: December 16, 1969
[ Z 205 IE]
German version: Angew. Chem. 82, 481 (1970)
Publication delayed at authors' request
[*I Priv.-Doz. Dr. H . B. Stegmann and F. Stocker
Chemisches Institut der Universitat
74 Tiibingen, Wilhelmstrasse 33 (Germany)
Dr. K. Scheffler
Present address: Conseil Europeen pour la Recherche
Nuclkaire
CH-1211 Geneve-Meyrin (Switzerland)
[ l ] Cf. e.g., E. Muller, F. Gunther, K . Scheffler, and H . Fettel,
Chem. Ber. 91,2888 (1958); G. Bahr and G. Zoche, ibid. 88, 542
(1955); R. Preckei and P . W . Selwood, J. Amer. chem. SOC.62,
2765 (1940); U.Belluco, G. Tagliavini, and P. Favero, Ricerca
sci. Rend. Suppl. A 32, 98 (1962); Chem. Abstr. 57, 13786
(1962).
121 H . B. Stegmann, K. Schefller, and F. Stocker, Chem. Ber.
103, 1279 (1970).
Preparation of Trieihyl Ortho-3-butynoate and its
Conversion into 5-0x0-3-alkynoate Esters and into
Derivatives of 3,5-Dioxoalkanoate Esters 111 [**I
By Rolf Finding and Ulrich Schmidt [*I
Dedicated to Professor Eugen Miiller on the occasion of his
65th birthday
In triethyl ortho-3-butynoate (4,4,4-triethoxy-l-butyne)( I )
[which we obtained from propargylmagnesium bromide and
tetraethyl orthocarbonate) masking of the carboxyl group
as orthoester protects i t from attack by alkali-metal acetylides
and prevents rearrangement of the acetylenic linkage t o the
a,P-position or to a n allenic unit. The orthoester can thus be
Angew. Chem. internat. Edit.
1 Vol. 9
(1970) f No. 6
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