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Experimental Methods for Estimating -Electron Densities -Moments and Atomic Dipole Moments of Aromatic Heterocyclics.

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A Phosphazene h i d e I l l
By Dr. H. Bock and Dipl.-Chem. W. Wiegrabe
Institut fiir anorganische Chemie
der Universitat Miinchen (Germany)
In the course of our investigations on the reactivity of the
phosphorus-nitrogen double bond we have isolated P-diphenyf-N-tosylphosphazeneazide (I) in 83 % yield.
+ MN-3
In contrast to the formal analogy with the tetrazole-azidoazomethine equilibrium [2], the infrared spectrum indicates the
exclusive existence of the azide form (I); no indication was
found for the phosphatetrazole structure (11).
We have carried out a total synthesis of Thiolutin@,starting
from N-methyl-1-ethoxycarbonyl-2diethoxyethylamine.
Treating this with methoxycarbonylacetyl chloride led to the
Nitrosation and acetylative reduction led to the
peptide (VI), which formed the pyrrolone (VII) on ester
condensation with elimination of the methoxy carbonyl group.
The enolic hydroxyl group in the 4-position reacted smoothly
with benzenesulfonyl chloride to form (VIII).
azide (m.p. 86 "C) decomposes above 220 OC with release of the calculated amount of
nitrogen; copper as catalyst lowers the decomposition point
to 120 O C . The unstable azene intermediate (111) formed on
thermal decomposition can be formulated as a 1,3-dipolein a
mesomeric structure [3] :
Reaction with the strained double bond of dicyclopentadiene
yields a crystalline 1 : 1 adduct (m.p. 144 "0.Whether this
compound is the aziridine (IV) formed through azene attack
or the Al-1,2,5-phosphadiazoline(V) formed by 1,3-dipolar
addition is still undecided.
(VII): X = H
(VIII): X = --SO~&HS
When the sulfonate (VIII) was allowed to react with NaSH
in alcohol, dihydrothiolutin (IX) was formed and was then
dehydrated with iodine to yield Thiolutin (I). The conversion
of natural Thiolutin into aureothricin and isobutyropyrrothin
by hydrolysis of the amide group and acylation has already
been reported [5]. Holomycin was synthetized analogously
starting from 1-ethoxycarbonyl-2-diethoxyethylamine.
Received, February 21 st. 1962
Received, November 21 st. 1961 I2 252172 IEl
[l] 2nd. Communication on inorganic aides. 1 st. Communication: H . Bock and K . L. Kompa, Angew. Chem. internat. Edit.
I , 264 (1962).
[2] See W. G. Finnegan, R . A . Henry, and E. Lieber, J. org.
Chemistry 18, 779 (1953); J. H . Boyer and E. J. Miller, J. Amer.
chem. SOC.80,4671 (1959).
[3] See R. Huisgen, Naturw. Rundschau 14,43 (1961).
Total Synthesis of the Antibiotics Thiolutin,
Aureothricin, and Holomycin
[Z 242119 IE]
[i] W. D . Celmer and J. A. Solomons, J. Amer. chem. SOC.77,
2861 (1955). Angew. Chem. 66, 745 (1954). Synopsis:The Merck
Index. 7th. Ed., Rahway, N. J., U.S.A. 1961, p. 1038.
[2] H . Umezawa et al., Jap. Med. J. 1, 512 (1948). Synopsis:
The Merck Index. 7th. Ed., Rahway, N. J., U S A . 1961, p. 112.
[3] D . S. Bhate et al., Experientia (Basel) 16, 504 (1960).
[4] L. Ettlinger, E. GZumann, R . Hiitter, W. Keller-Schierlein, F.
Kradover, L. Neipp, V . Prelog, and H . Zahner, Helv. chim. Acta
42;563 (1959).
[ 5 ] W. D . Celmer and J. A. Solomons, Antibiotics Annual
Experimental Methods for Estimating
n-Electron Densities, x-Moments, and Atomic
Dipole Moments of Aromatic Heterocyclics
By Dr. U. Schmidt and DipLChem. F. Geiger
By W. Seiffert, Dr. H. Zimmermann, and Dr. G. Scheibe
Chemisches Laboratorium
der Universitat Freiburg/Breisgau (Germany)
Thiolutin@ (I) [l] and aureothricin (11) [2] are antibiotics
which are active against pathogenic fungi, and Gram-negative
and Gram-positive bacteria. Recently, two other closely
related antibiotics, isobutyrylpyrrothin (111) [3] and holomycin (IV) [4], were isolated from Streptomyces species by
Bhate et al. and by Prelog and a Ciba research team. Total
syntheses of this group of antibiotics, which contain condensed pyrrolonedithiol ring systems, have not yet been reported.
Angew. Chem. internat. Edit.
Vol. I (1962) / No. 5
Physikalisch-ChemischesInstitut der
Technischen Hochschule Munich (Germany)
Proton magnetic resonance spectra of aromatic heterocyclics
in dilute solution in nonpolar solvents (4 mole- % in hexane)
were used for estimating the x-electron densitities in the
molecular ground state. A reference spectrum, based on the
ring current model of Wuugh and Fessender [I], is calculated
fist. This applies to a molecule with a fictitious x-electron
density of q = 1 per ring atom as occurs for example, in the
case of benzene. Any difference (A6) in the chemical shift of
a proton signal between the spectrum determined experimentally and the reference spectrum is to be attributed to a
difference between the shielding of the proton in the real
molecule and that in the model with q = 1. A 8 is therefore a
measure of the deviation from q = 1 of the x-electron density
on the carbon atom in the ring carrying the hydrogen atom
investigated. The proportionality factor between A 8 and the
x-electron density can be determined from the chemical shift
of the signals of the cyclopentadienyl anion, the tropylium
cation, and benzene. The x-electron density per carbon atom
is q = 1 for benzene, q * 615, for the cyclopentadienylanion,
and q * 617 for the tropylium cation. A calibration curve
indicating the quantitative relationship between 1-q and A 8
can be constructed using these values [2].
This calibration permits calculation of 1-4 for pyrimidine
from the experimental A 8 values, and hence of the x-electron
density distribution in the ground state. Table 1 gives the
values of the densities determined experimentally and the
corresponding values derived by quantum mechanics. The xelectron density of the nitrogen atoms was determined from
the equation Xi (1-qj) = 0 (i = total number of atoms).
Table 1. CalcuIated and measured values of q for pyrimidine
(I): X = OCH,
(11): X = SCH3
(IV): X = Br
++ CHz=Xel
Whereas, in dilute alkalis, (1) only decomposes on boiling,
addition of 1 N NaOH to a cold aqueous solution of 11 causes
immediate quantitative separation of triphenylphosphine
oxide and dimethyl sulfide. A novel, intra-anionic phenyl
migration [5] leading to benzyldiphenylphosphine oxide (V)
(17 % from 111, 33 % from IV) competes with the elimination
of methyl halids from (111) and (IV). This phenyl migration
can also be brought about in anhydrous medium by the action
of excess n-butyl-lithium or phenyl-lithium on 111. The
organometallic reagent first releases the ylene (VI) [I]:
nitrogen atoms can be estimated at ca. 0.8 D. If a C-N bond
moment differing from zero does exist, the value of 0.8 D
represents the upper limit of the atomic moment of the free
electron pair on the nitrogen.
[Z 232177 IE]
[l] J. S. Waugh and R . W. Fessender, J . Amer. chem. SOC. 79, 846
[2] This procedure was applied to azulene independently by H.
Spieseeke and W. G. Schneider, Tetrahedron Letters 14, 468
(1961), and by G. Fraenkel ef ai., J. Amer. chem. SOC.82, 5846
[3] P. Lowdin, J. Chem. Phys. 19, 1323 (1951).
[4] H . F.Hameka and A . M . Liquori, Molec. Phys. 1 , 9 (1958).
Rearrangement and Degradation of u-Heterofunctionally Substituted Phosphonium Salts
By Dr. M. Schlosser
Organisch-Chemisches Institut
der Universitat Heidelberg (Germany)
On degradation of phosphonium salts with alkalis to form
phosphine oxides, the ligand which is the most stable anion is
split off. In the case of methoxymethyltriphenylphosphonium
I .204
The x-electron densities in column 2 were calculated by
Ldwdin [3], using the electronegativity factor 8~ = 0.6; the
values in column 4 are from Hameka and Liquori [4], who
used &N = 0.4. The smaller the value of 8~ selected, the
closer the value of q approaches unity. Our experimental
values favor 8~ M 0.5.
The x-moment derived from the experimental values of qi
is 1.0 D. The resulting cr-moment of pyrimidine is calculated
from the CH-bond moments to be 0.6 D by assuming the
CC- and CN-bond moments to be zero. This value has been
postulated for the CN-bond moment [4]. The figures
given in the literature for the CN-moment are generally too
high, since they may contain portions of the atomic dipole
moment of the N atom. From the dipole moment of pyrimidine of 2.42 D [3], the atomic dipole moment of the
Received, February 26th. 1962
chloride (I) [I], a phenyl group IS eliminated 12J.However,
the aliphatic group is stabilized as an anion, and its elimination is therefore favored, if the oxygen in (I) is replaced by a
heteroatom capable of d-orbital resonance (I1 [I], I11 [I],
and IV [4]):
The benzylidenephosphoranes (VIII) and (IX) can be detected by the Wittig reaction (VIII + benzaldehyde + stilbene)
or by hydrolysis (IX + HBr + 62% benzyltriphenylphosphonium bromide). Triphenylphosphine is formed in a side
reaction in the aqueous alkaline degradation (10 % from 111,
3 % from 1 9 , but is not formed in the non-aqueous medium.
In contrast to the formulation given by Hellmann and Bader,
who also observed the phenyl migration in aqueous alkaline
solution [6], these results seem to indicate that the NaOH,
too, probably first deprotonizes (III) to the ylene (VI) [31.
Addition of a further hydroxyl ion produces the anion (VII)
(R = OH), which then rearranges to (X). Compound (X)
tautomerizes to (V).
Received, March 5th. 1962
[Z 240/80 IEI
[I] G. Witrig and M . Sehiosser, Chem. Ber. 94, 1373 (1961).
[2] C. K . Ingoid, J. Chem. SOC.(London) 2342 (1929); 531 (1933).
[3] W . von E. Doering and A. K . Hoffmann,J. Amer. chem. SOC.
77, 521 (1955).
[4] G. Kobrich, Angew. Chem. internat. Edit. I , 51 (1962). I wish
to thank Dr. Kobrich for the starting material.
[5] Cf. similar rearrangementsobserved by G . Wittig and H . b i b ,
Liebigs Ann. Chem. S80, 57 (1953); A . W . Johnson and J. C.
Tebbe, J . chem. SOC.(London) 2126 (1961).
161 H . Hellmann and J. Bader, Tetrahedron Letters 724 (1961).
Imides by the Reaction of Unsaturated Amides
with Carbon Monoxide
By Dr. J. Falbe and Prof. Dr. F. Korte
Shell Grundlagenforschung-GmbH.,
Schloss Birlinghoven (Germany)
Aliphatic and alicyclic m,P- and P,y-unsaturated carbonamides
react with carbon monoxide in the presence of Raney cobalt,
cobalt salts, and cobalt carbonyls at 160-280 OC and 100 to
300 atm. to produce succinimides or glutarimides in 65-95 %
yield. For example, acrylamide gives succinimide in 81 %
Angew. Chem. internat. Edit. VoI. 1 (1962) 1 NO.5
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experimentov, moment, densities, method, atomic, electro, estimating, heterocyclic, aromatic, dipole
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