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Synthesis of Pteridine 8-Ribosides.

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It is here seen that chloro(chloroformy1)sulfane reacts only
monofunctionally. Attempts to replace also the CI atom of
the chloroformyl group by the trifluoromethyl group failed.
This accords with findings by Zumnch and KiihIersJ in which
ClCOSCl was attacked by thiols only at the S-bonded CI
atom.
Compounds ( I ) and (2) are water-clear, mobile liquids
which are stable in absence of moisture (see Table).
Received: March 9, 1970; revised: March 25, 1970 [Z 208 IE]
German version: Angew. Chem. 82, 484 (1970)
[*I Prof. Dr. Dr. A. Haas, Dr. H. Reinke, and
Dip1.-Chem. J. Sommerhoff
Lehrstuhl fur Anorganische Chemie 11 der Universitat
463 Bochum, Postfach 2148 (Germany)
[**I Part 3 of Chemistry of F-C-S Compounds. - Part 2: [2].
[l] B. H . Tattershall and G. H . Cady, J. inorg. nuclear Chem.
29, 2819 (1967).
121 See A . Haas and D . Y . Oh, Chem. Ber. 102, 77 (1969).
131 Philips HPK Type 57203 B/OO, 125 W.
141 A . Haas and W . Klug, Chem. Ber. 101, 2617 (1968).
[5] G . Zumach and E . Kiihle, Angew. Chem. 82, 63 (1970);
Angew. Chem. internat. Edit. 9, 54 (1970).
Direct Synthesis and Reactions of
Bromo(pentafluoropheny1)silanes 111
By Manfred Weidenbruch and Nezam Wessal[*l
Halo(pentafluorophenyI)silanes, which are of interest for the
preparation of novel polysiloxanes, cannot be obtained by
reaction of silicon tetrahalides with (pentafluoropheny1)magnesium bromide o r -lithium because, even with a large
excess of the Six4 components, only tetrakis(pentafluor0pheny1)silane is formed [21. We have now found that a direct
synthetic process [31 affords them easily and with a selectivity
that is remarkable for perhalogenated compounds.
For instance, brornopentafluorobenzene reacts (optimum
temperature: 600 "C) with a catalyst composed of silicon
(85%) and copper (15%) t o give 60% of dibromobisbentafluoropheny1)silane ( I ) , b.p. 110 'C10.6 torr, and 30% of tribromo(pentafluoropheny1)silane (2), b.p. 205-208 "C, together with a little bromotris(pentafluorophenyl)silane, m.p.
83 "C:
Conversion of C6FsBr amounts to 10-30%, which indicates
the advisability of a recycling technique in which the unused
CsFsBr, b.p. 136 "C, is continuously distilled off fractionally
from the less volatile products and returned to the heated
catalyst. Decafluorobiphenyl (3), m.p. 68 'C, b.p. 188 OC, is
the only by-product formed in detectable amounts; the
proportion of (3) formed depends on the copper content of
the catalyst and produces difficulties if it exceeds 20%. On
pure copper C6FsBr gives (3) quantitatively at 600 'C.
Chloropentafluorobenzene reacts analogously, giving chloro@entafmorophenyl)silanes, though the conversion is, as expected, lower because of the greater bond energy of R-CI
than of R-Br. Hexafluorobenzene does not react with the
Si/Cu catalyst up t o 600 OC.
Applicability of compounds ( I ) and (2) to synthesis of
further pentafluorophenyl-substituted silanes and polysiloxanes is indicated by the annexed chart of some reactions
of ( I ) :
Heating ( I ) or (2) with antimony trifluoride leads to the
fluorosilanes (41, b.p. 207 OC, and C6F5SiF3, b.p. 102 "C,
respectively, which, like bromosilanes, react spontaneously
with water. Hydrolysis of ( I ) and similarly of ( 4 ) proceeds
via the stable silanediol (51, m.p. 12@-122"C,
which condenses at the melting point to give the resinous polysiloxane
( 6 ) ,m.p. > 170 "C. On prolonged heating or o n storage, ( 6 )
changes, without alteration in composition, to a silicone
that is very resistant both thermally and chemically and has
celluloid-like properties, melting at > 350 'C.
Received: March 28, 1970
[Z 211 IEl
German version: Angew. Chem. 82, 483 (1970)
[ * ] Dr. M . Weidenbruch and Dipl.-Chem. N. Wessal
Institut fur Anorganische Chemie und Elektrochemie
der Technischen Hochschule
51 Aachen, Templergraben 55 (Germany)
[l] Pentafluorophenyl Compounds, Part 3. - Part 2: M ,
Schmeisser, N . Wessal, and M . Weidenbruch, Chem. Ber. 101.
1897 (1968).
[2] L. A . Wall, R . E. Donadio, and W. J . Pummer, J. Amer.
chem. SOC.82, 4846 (1960).
[3] For a review, see V . Baiant, J . Joklik, and J . Rathousk9,
Angew. Chern. 80, 133 (1968); Angew. Chem. internat. Edit.
7, 112 (1968).
C O N F E R E N C E REPORTS
Synthesis of Pteridine 8-Ribosides
By Wolfgang Pf?eiderer[*l
The synthesis ofpteridine 8-ribosides ( I ) , the structural analogs
of the purine nucleosides (21, has been the focal point of our
investigations in the field of pteridines for more than twelve
years.
Previous investigations o n the glycosidation of 7-oxo-7,8dihydropteridines by the heavy-metal salt method have shown
that 7-0 glycosides are always formed and no N-8 glycosides [I]. The analogous behavior of the 2-oxodihydroquinoxalines 121 and of 2-pyrazinone [31 helped to clarify the complex nature of the reaction and showed that the observed
selectivity in the direct glycosidation of the pteridine system
Angew. Chem. internat. Edit. f Vol. 9 (1970) No. 6
under such conditions is determined primarily by two factors
steric hindrance and the particular electronic features of the
pyrazine system - both of which oppose a n O + N transglycosidation.
467
The first definite synthesis of a pteridine 8-glucoside was
accomplished in 1964 (41 using 4-amino-6-dimethylaminopyrimidine as starting material. The carbohydrate group was
introduced into the molecule at the pyrimidine stage; amination at C-5 via the benzeneazo derivative followed by cyclization with a-0x0 esters completed the synthesis. A further
successful variant was found for the synthesis, namely the
reaction of 4-chloro-5-nitropyrimidines
with 1 -aminohexoses
to give 4-glycopyranosylamino derivatives which, on reduction and cyclization, afford the 7-0~0-7,8-didydropteridine
8-glycopyranosides [51. Since attempts to use this method of
synthesis in the ribofuranose series failed because of the instability of l-amino-2,3,5-tribenoylribofuranose,a new
preparative route was developed on the basis of a fusion
reaction. For instance, 4-amino-5-nitropyrimidines (3) and
(4)react with fully acylated sugars such as l-acetyl-2,3,5-tribenzoylribofuranose (5) on fusion in the presence of acid
catalysts[61. The 4-amino groups of (3) and ( 4 ) undergo ribosidation in good yield if the reactants are heated for
30 mins at 160 “C in the presence of ZnCl2 as catalyst. Separation of the reaction mixture by layer chromatography
showed that a mixture of anomers is formed under such
vigorous reaction conditions and that the a-riboside (6) is the
predominant product in each case. Assignment of the pure
ribosides to the a- and p-series was established by analysis of
the NMR spectra and by decoupling experiments. No definite
conclusions could be drawn from the ORD spectra.
I
(31, R = H
OBZORZ
(5)
R
R
[l] W. Ppeiderer and R. Lohrmann, Chem. Ber. 95, 7 3 8 (1962);
W. Ppeiderer and F. Reisser, ibid. 95, 1621 (1962); 99, 536 (1966)
121 F. Reisser and W. Ppeiderer, Chem. Ber. 99, 547 (1966).
131 F. Reisser and W. Ppeiderer, Chem. Ber. 99, 542 (1966).
[4] W. Ppeiderer and D. So//, J. heterocyclic Chem. I , 23
(1 964).
[SI W. Pfleiderer and E. Biihler, Chem. Ber. 99, 3022 (1966).
161 H . Rokos, Dissertation, Universitat Stuttgart 1967.
Recent Work on Insect Sex Attractants
By Karl Eiter [*I
The insect sex attractants found so far belong to one of the
following classes: Singly or multiply unsaturated, straightchain or slightly branched alcohols and their esters; olefinic
carboxylic acids and their esters; heterocyclic and aliphatic
substances resembling terpenes.
The sex attractant of the gypsy moth (Porfhetria= Lymantria
dispar), reported to be (+)-l-hexyl-lO-hydroxy-3-cis-decenyl
acetate and synthesized stereospecifically by Jacobson e f al. (11
has been prepared by us (21 and by Stefanovic et al. 131 in a
stereospecifically uniform synthesis and found to posses no
biological activity. The explanation offered by the American
authors [I], namely that the activity is inhibited by contamination with small amounts of the trans compound, was shown
to lack any substance since mixtures of the synthetic material
with active extracts exhibited a definite activity in an electroantennogram (EAG) [**I. Jacobson et al. [I] have further described the synthesis of l-hexyl-12-hydroxy-3-cis-dodecenyl
acetate, “gyplure”, which is reported to be just as active as the
gypsy moth attractant. We have also synthesized this substance stereospecifically and found it to be completely inactive. It follows that the structure given for the gypsy moth
attractant cannot be correct.
Isolation and structural elucidation of the sex attractant of
the American cockroach (Periplaneta americana) were also
reported by Jacobson et al.; after publication of a total synthesis of this cyclopropane derivative by Day and Whiting[4],
which yielded a biologically inactive product, they later
retracted their claims.
The sex attractant of the pink bollworm moth (Pectinophora
gossypiella S.) is given by Jacobson et al. 151 as lO-propyl-5frans,9-tridecadien-l-ol, “propylure”. On carrying out a
sterically non-uniform synthesis we obtained a product
completely lacking activity. Jacobson [61 repeated the synthesis and isolated the pure trans compound from the mixture
of isomers. The presence of 15-20% of the cis compound
was said to inactivate the attractant completely. This finding
is the same as in the case of the gypsy moth attractant and
rather unlikely, particularly in view of reports that the activity of propylure in field tests depends on the presence of
: mosquito repellent
activators (N,N-diethyl-m-toluamide
Autan @) 171 and that 7-cis-hexadecenylacetate, “hexalure”, is
considerably more active than propylure and is not inhibited
by the trans compound [81.
HoHzcd
OH OH
Surprisingly, it was found that the pure anomers (6) or (7)
are partially anomerized to the pteridine-N-8-riboside during
both the catalytic hydrogenation of the 5-nitro to the 5amino group and the reaction with glyoxylate. Compounds
(8)and ( 9 ) could be separated by preparative layer chromatography.
Lecture at Wuppertal, April 8, 1970 IVB 237 IE]
German version: Angew. Chem. 82, 450 (1970)
In the present state of uncertainty regarding their mode of
action, the pheromones of other insects, which are possibly
only quantitatively definite mixtures of three or four synergically acting components, can hardly be used as models for
studies on the problem whether insect pests can be attracted
specifically to some central position. This paramount question
of modern pest control still cannot be answered owing to the
confusion present in this field of research.
Lecture at Kiel on April 16, and
at Erlangen on May 29, 1970 IVB 238 IEI
German version: Angew. Chem. 82, 485 (1970)
[*I Priv.-Doz. Dr. K. Eiter
[*I Prof. Dr.
W. Pfleiderer
Fachbereich Chemie, Universitat
775 Konstanz, Jakob-Burckhardt-Strasse(Germany)
468
Farbenfabriken Bayer,
Wissenschaftliches Hauptlaboratorium
509 Leverkusen-Bayerwerk(Germany)
Angew. Chem. internat. Edit.
/ Vol. 9 (1970) / No. 6
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