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Jacobson and Heintschel Peroxides.

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tcmc ligand precipltated out during the course of the reaction and was recrystallized
from boiling ethanol/water: yield 61 %. Synthesis of a similar ligand has been
reported [19]. Ln(SO,CF,), (0.63 mmol) in 75 mLofanhydrousethanol was treated
with tcmc (0.250 g, 0.63 mmol) in 225 mL of ethanol. The mixture was heated at
reflux under nitrogen for 3.5 h following the dissolution of tcmc. The solution was
concentrated in vacuo, and hexane was added until cloudiness was observed. For
ELI” and La” complexes, crystals formed within about 12 h. The Dy3+ complex
was isolated as a powder. Yields were greater than 55%. Satisfactory microanalytical data were obtained for all compounds ‘ H N M R (CD,CN): [La(tcmc)](CF,SO,j, ( - 10 ’C): 6 = 2.42 (NCH, (equatorial), d. J(C,H) = 14.8 Hz), 2.56
(NCH2 (equatorial). d. J(C,H) =13.6 Hz), 2.85 (NCH, (axial), pseudo t), 3.35
(NCH, and CH,C(O)NH,. m), 3.84 (CH,C(O)NH,. d, J(C,H) = 16.4 Hz), 7.27
(NH,, s). 7.81 (NH,. s): (75°C): 2.69 (NCH,, br.), 3.03 (NCH,, br.), 3.65 (CH,C(O)NH,. a ) , 7.08 (NH,. s). 7.68 (NH,. s). ”C N M R (CDJN): [La(tcmc)](CF,SO,), ( - 20 C ) : 6 = 50.1, 54.3 (NCH,. ring), 5X.9 (NCH,. amide), 178.X
(C(O)NH,). [Eu(tcmc)](CF,SO,), (19°C): d: =76.3, 91.5, 110 (NCH, ring and
amide). 198.3 (C(O)NH,). Kinetic measurements of R N A cleavage were made as
described previously [2a, 201.
Received: September 20, 1993
Revised: December 15, 1993 [Z6368IE]
German version: AnxCw. Chem. 1994, 106, 824
[ l ] a) R . Breslow. D.-L. Huang, Proc. Nafl. Acad. Sci.U S A 1991,88.4OXO;b) M.
Komiyama. K . Matsumura. Y. Matsumoto, J Chem. SOC. Chem. Conzmun. 1992, 640; c) B. F. Rordorf, D . R. Kearns, Biopolymers 1976, is,
1491.
12) a) J. R. Morrow. L. A. Buttrey, V. M. Shelton, K. A. Berback, J A m . Chem.
Soc. 1992. 114. 1903; b) J. R. Morrow, K . 0. A. Chin, Inorg. Chern. 1993, 32.
3357. c) J. R. Morrow, S. Amin, C. H. Lake, M. R . Churchill, {bid. 1993, 32,
4566. d j K. 0. A. Chin, J. R. Morrow. C . H . Lake. M. R. Churchill, Inorg.
(%ern.1994. 33, 656.
[3] a) C. A. Stein, J. S. Cohen, Cancer Res. 1988, 48, 2659; b) E. Uhlmann, A.
Peyman, Chem. Rev. 1990, YO, 544; c) J. Goodchild, Bloconjugate Chem. 1990,
I, 165; d j U . English, Angeqea.. Chem. 1991. 103, 629; Angew. Chern. Inf. Ed.
Engi. 1991. 30. 613.
[4] a) J A. Davies. F. R. Hartley, S. G . Murray, Inorg. Chim. Acta 1980, 43, 69;
b) V N . Krishnamurthy, S. Soundararajan, J Inorg. Nucl. Chem. 1967, 29,
517
[ S ] J. F. Desreux, Inorg. Chern. 1980, 19, 1319.
[6] X. Wang, T. Jin. V. Comblin, A. Lopez-Mut, E. Merciny, J. F. Desreux, Inorg.
Chem. 1992, 31, 1095.
[7] C. A. Chang, Eur. J. Solid State Inorg. Chem. 1991. 28, 237.
[XI S. Aime, P. L. Anelli, M. Botta, F. Fedeli, M. Grandi. P. Paoli, F. Uggeri, Inorg.
Chem. 1992. 31, 2422.
[9] M. F. Tweedle. J. J. Hagan. K. Kumar, S. Mantha. C. A. Chang, M a p . Reson.
Imaging 1991. 9. 409.
[lo] M. S. Konings. W. C. Dow, D. B. Love, K. N . Raymond, S. C. Quay, S. M.
Rocklage. Inorp. Chem. 1990, 29, 1488.
[l 11 In buffered solutions (10 mM (4-(2-hydroxyethyl)piperazino)ethanesulfonic
acid (Hepes)) at 37‘C. first-order rate constants for cleavage of A,, to A,,
oligomers at pH 7.6 and for transesterification of 2 at pH 7.4 in the absence of
catalyst are 2.3 x lo-’ h-’ and 5.4 x
h - ’ , respectively. Because the pseudo-first-order rate constant for the catalyzed reaction is dependent on the
concentration of lanthanum complex, calculation of rate enhancements awaits
the determination of true first-order rate constants for catalysis, which may be
obtained through saturation kinetic studies or by the determination of binding
constants.
[12] [Ln(edta)]- complexes are inactive in RNA cleavage (ref. [Za]).
[13] M -R. Spirlet, J. Rebizant, J. F. Desreux, M.-F. Loncin. Inorg. Chem. 1984, 23.
359.
[14]C. A. Chang. L. C. Francesconi, M. F. Malley, K . Kumar, J. Z. Gougoutas.
M F. Tweedle. D. W Lee, L. J. Wilson, Inorg. Chem. 1993, 32, 3501.
[15] S. Amin. J. R. Morrow, C. H. Lake. M. R. Churchill, unpublished results.
[I61 Colorless crystals (0.4 x 0.27 x 0.2 mm) were mounted on a n upgraded Siemens
P2,:P3 diffractometer. Data were collected through the use of the coupled 20/w
scan technique. A total of 5469 reflections were collected (Mo,,, E. = 0.71073,
2 0 = 5-45 ) and were merged into a unique set of 5061 reflections (R,,, =
0.0116). All data were corrected for Lorentz and polarization effects. An empirical absorption correction was also applied to the data set. The crystal
belongs to the triclinic system, space group Pi. a =10.019(1), b =12.754(2),
c =16.116(3).&. a=96.614(14).
/l
=92.035(13). y=108.960(12)‘, V =
1928.8(6) .&’and Z = 2. All crystallographic calculations were carried out with
the Slemens SHELXTL PLUS program package (171. The analytical scattering
factors for neutral atoms were corrected for both the Af and iAf” components
of anomalous dispersion [l 81. The structure was solved by means of a Patterson
map. Refinement of parameters was achieved through the minimization of the
function ~iv(lFo\-IFcl)z.
The extreme features on the final difference-Fourier
map were a peak of height 0.53 e k 3 and a negative feature of -0.84 e k ’ .
Refinement converged with R = 0.0260 and R, = 0.0283 for 542 parameters
A n g w U i e m 1111. Ed. Engl. 1994, 33, No. 7
refined against those 4169 reflections with IFD\>60(FoI and R = 0.0358 for all
5061 data. Further details are available on request from the Director of the
Cambridee CrvstalloeraDhic
- . Data Centre, 12 Union Road, GB-Cambridge
CB2 l E f ( U K ) .
.I171_SHELXTL PLUS, Siemens Analytical Instruments, Madison, WI, USA, 1990.
[18] Infernafional Tables /or X-ray Cry.dlogruphy Vo/. 4, Kynoch, Birmingham.
U K , 1974; Vol. 4, pp 99-101. 149-150.
[19] R. Kataky, D. Parker, A. Teasdale, J. P. Hutchinson, H. J. Buschmann, J.
Chrm. Sor. Perkin Fans. 2 1992, 1347.
[20] M. K. Stern, J. K. Bashkin, E. D. Sall, .
I
A m . Chem. Soc. 1990. 112. 5357.
Jacobson and Heintschel Peroxides**
Sei-Hum Jang, Prakash Gopalan, James E. Jackson,*
and Bart Kahr*
In 1908, Schmidlin[’] titrated solutions of Gomberg’s[’’
triphenylmethyl radical (1a) with oxygen and demonstrated
that the revolutionary, hypovalent carbon species was in equilibrium with an unreactive one. Molecular weight determinations in anaerobic solutions[31indicated a dimer for which several structures had been proposed : Markownikoff (1 902) insisted
upon hexaphenylethane (2) ,[41 Heintschel (1903) proposed a
“tail-to-tail’’ or para-para coupling (3),15]and Jacobson (1 905)
favored a “head-to-tail’’ or methyl -para coupling (4) .r61 After
a decade, Gomberg settled on 2, which became entrenched as
the consensus choice.[71However, NMR studies in 1968 confirmed Jacobson’s proposal (4), much to the surprise of the
many scientists who had assumed that 2 was the correct structure.’*I In his 1974 review, McBride uncovered neglected chemical evidence that should have supported Jacobson, and argued
that democracy is not always the best way to make scientific
judgemen ts.Igl
Another dimer-bis(triphenylmethy1)peroxide
(5)1’01-was
the product in Schmidlin’s titration. In fact, the ready formation
of this peroxide on exposure of solutions of triphenylmethyl to
air forced Gomberg to conclude that he had prepared a novel,
reactive species in 1900.[21It since has been assumed that only
methyl-methyl coupled peroxides, like 5, are produced from
triarylmethyls and oxygen. Herein, we describe the preparation
and characterization of Jacobson and Heintschel peroxides in
which triarylmethyl radicals add oxygen between methyl -para
(6) and para-para positions (7), respectively. Presumably,
analogous peroxides long have been present in many triarylmethyl radical oxidations.
We recently proposed a scheme for assembling molecular
magnetic materials based on complexation of the stable free
radical, tris(2,6-dimethoxyphenyl)methyl (1c), with metal
cations.[”’ As part of this work we determined the crystal structure of I C . [ ’ ~It] displays an anomalous conformation far from
the symmetrical D, ground state expected from ESR spect r o ~ c o p y [ ’14]
~ . (Fig. 1) and molecular orbital calculations (see
next paragraph). Two aryl rings are twisted out of the plane of
[*I
Prof. D r J. E. Jackson, Dr. S:H. Jang
Department of Chemistry and Center for Fundamental Materials Research
Michigan State University
East Lansing, M I 48824-1322 (USA)
Telefax: Int. code (517)353-1793
+
Prof. Dr. B. Kahr, Dr. P. Gopalan
Department of Chemistry, Purdue University
West Lafayette. IN 47907-1 393 (USA)
Telefax: Int. code (317)494-0239
This work was supported by the National Science Foundation.
+
[**I
‘C? VCH Veriugsg~,.~elis~ha/l
mbH. 0 - 6 9 4 S f Weinheim, 1994
0S70-0833/94j0707-0775 8 fO.00+ .2S,’fJ
115
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2
6a
6b
7a
7b
R=H
R=OCH,
R=H
R=OCH,
Scheme 1. Triarylmethyl dimers and peroxides.
coordination of the central carbon atom by 61", while the third
ring is twisted by only 22". This conformation is similar to the
transition state structure for the two-ring flip enantiomerization
mechanism in Ar,Z propeller^."^]
Fig. 1. Schematic illustration of the two-ring flip enantiomerization showing the
near equivalence of the transition state (TS) with the conformation of l c in the
crystal (bottom)
We surmised that a tetra-ortho-substituted radical such as 1 b
might have a ground state geometry that resembled the crystallographic conformation of 1c. ENDOR studies of 1 b by Ishizu
et a1.['6] qualitatively support these expectations, yielding twist
angles of 65" for the substituted rings and 30" for the unsubstituted rings. Calculations of the molecular structure of 1 b with
the AM1 Hamiltonian["] were consistent with the ENDOR
geometry. The structure was found to have C , symmetry with
twists of 10" for the unsubstituted ring and 61" for the substituted rings. By contrast, the calculated ring twists for the hexamethoxy radical (1 c) were 46"."*l
In 1 b, the twist angles of two rings are increased, relative to
those of the unsubstituted triphenylmethyl, by the out-of-plane
deforming ortho substituents; the unique ring can now turn to
an orientation nearly in the plane of coordination of the methyl
776
0 VCH
Vrrlugsgrsell.whafi mbH. 0-69451 Weinheim.1994
carbon. In this way, 1 b maximizes its spin density at the para
position of one ring while sterically hindering the methyl center.['gl The reactivity of such a radical should be concentrated at
this para position.
Solutions of 1 b were allowed to stand in air for three days
after which yellow-brown crystals were collected. Single-crystal
X-ray analysis revealed a Jacobson peroxide 6 b (Fig. 2) in which
oxygens link the central methyl position of one and the paru
position of the other triarylmethyl subunit.'*'] In contrast to 5,
which was centrosymmetric in the crystal with a peroxide dihedral
angle of 180", C17-010-09-C20 was measured as 127.6(4)' in 6b.
The latter is much closer to the standard value of approximately
110" for the skew conformation in dialkyl peroxides.[''' Other
geometric parameters such as the 0-0 bond length and C - 0 - 0
valence angles compare favorably with 5 (see legend to Fig. 2).
Martin et al. noted that solutions of 1c react slowly with
oxygen in the air to give an orange-brown precipitate.[l3I Our
attempts to recrystallize this material gave single crystals too
small for X-ray analysis. As with 6b, acid treatment of the
oxidation product of 1c gives the corresponding triarylmethyl
n
co 1
C03
Fig. 2. ORTEP representation (50 % probability ellipsoids) of the crystal structure
of 6b.Selected bond lengths [A] and angles ["I are followed by the corresponding
parameters for bis(triphenylmethy1)peroxide in square brackets. 0 9 - 0 1 0 1.473(5)
[1.480], C17-010 1.466(6) and C20-09 1.471(6) [1.461] C17-010-09 106.7(4)C20-09-010 108.1(4)' (107.51.
05?0-0833194/070?-0776 $ 10.00 + ,2510
Angew. Chem. I n t . Ed. Engl. 1994, 33, No. 7
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cation. Elemental analysis and FAB mass spectrometry established the composition as C,oH5,0,,, consistent with a peroxide. The structure of 7 b was determined by ' H N M R spectroscopy. Para attachment is indicated by the presence of the
methine and olefinic protons giving the pattern characteristic of
an AABB'C spin system. This spectrum, in contrast to that of
6b, results from a symmetric or Heintschel peroxide; the radical
l c undoubtedly forms a compound in which the dioxygen
bridge joins para positions.
Like the Jacobson dimer of triarylmethyl radicals, Jacobson
and Heintschel peroxides, the common oxidation products in a
variety of triarylmethyl radical studies, have escaped the attention of chemists for generations. These structures raise a concern : Why are not all bis(triarylmethy1)peroxides methyl-paracoupled in a Jacobson configuration? It previously has been
shown that large radicals such as the tert-butoxy radical prefer
to attach to para positions of triarylmethyls.[221Such behavior
has not been observed for oxygen. But since the first formed
peroxy radical (a large radical by most standards) must attach
to the second triarylmethyl radical we always might expect attack at the less hindered para site. Experiments are in progress
to determine the first position bound in the formation of 6b.
Experimental Procedure
[3] M. Gomberg, Ber. Dtsch. Chem. Ges. 1901, 34, 2726; M. Gomberg, L. H.
Cone, ihid. 1904, 37, 2033.
[4] V. W. Markownikoff*Zh. R u s ~ Fiz.-Khim.
.
0-vu. L902, 34. 140.
[5] E. Heintschel, Eer. Dtsch. Chem. Ges. 1903, 36, 320, 579.
[6] P. Jacobson, Eer. Dtsrh. Chrm. Ges. 1905, 38, 196.
[7] M. Gomberg, J. Am. Chem. Soc. 1914. 36, 1144.
[XI H. Lankamp. W. T. Nauta, C. MacLean, Tetruhedron Lett. 1968. 249; H.
Lankamp, Dissertation, Freie Universitit Amsterdam, 1970; see also: H. Volz,
W. Lotsch, H:W. Schell, Tetrahedron 1970. 26. 5343.
[9] J. M. McBride, Trfruhedron 1974, 30, 2009.
[lo] For crystal structures of bis(triphenylmethy1)peroxide (5) see C. Glidewell.
D. C. Liles, D. J. Walton. G M. Sheldrick, Actu Crystallopr. Spct. B 1979. 35.
500; A. 1. Yanovskii, T. V. Timofeeva, N. G. Furmanova, Yu. T Struchkov,
L. Yu. Ukhin. V. V . Bessonov. SOY.Phys. Crystullopr. Engl. Trunsl. 1981, 26,
112.
[ l l ] S.-H. Jang, R. A. Bertsch. J. E. Jackson. B. Kahr. Mol. Cr.s.sf. Liq. Crvst. 1992,
211. 289.
[12] B. Kahr, J. E. Jackson, D. L. Ward, S.-H. Jang, Actu Crysrallqr. Sect. B 1992.
48, 324; For a comparison of triarylmethyl geomtries in the solid state see
B. Kahr, D. Van Engen, P. Gopalan. Chem. Muter. 1993, 5. 729.
[13] J. C. Martin. R. G. Smith, J. Am. Chem. Sor. 1964.86, 2252.
[14] M. J. Sabacky, C. S. Johnson, Jr.. R. G. Smith, H. S. Gutowsky. J. C. Martin,
J. Am. Chem. Soc. 1967.89, 2054.
[15] K. M. Mislow. Arc. Chem. Res. 1976, 9, 26.
[16] K. Ishizu, K. Mukai, A. Shibayama, K. Kondo, Bull. Chem. SO'. Jpn. 1977,50,
2269.
[17] M. J. S. Dewar, E. ti. Zoebisch, E. F, Healy, J. J. P. Stewart. J. Am. Chem. SOC.
1985, 107, 3902.
[18] This value is in excellent agreement with the twist angle originally predicted by
ESR data [14].
[19] It would have an electronic structure that would mimic the transition state in
the two-ring flip enantiomerization (see Fig. 1).
[20] Crystals of 6 b suitable for single crystal X-ray analysis were obtained as described in the Experimental Procedure. C,,H,,O,,,
M =758.87 g . mol-I,
monoclinic. a = 9.398(1) A, h = 27.900(2), c = 15.259(2)A. /3 = 96.87(1),
V = 3972(1) A3. space group P2,/n, 2 = 4, ~(CU,,)= 6.88 cm-I.
eoald=1.269 g ~ m - ~3031
, unique, observed ( I > 3.0u(f)) reflections with
2 0 < 116". R = 0.062, R , = 0.080. The intensities were measured on an EnrafNonius CAD4 diffractometer with w-28 scans. The structure was solved by
direct methods (SHELX-86: G. M. Sheldrick, Institut for Anorganische
Chemie der Universitat Gottingen, F.R.G. 1986) and non-H atoms were refined anisotropically using the programs in MolEN (C. K. Fair, MolEN Structure Determination system, Delft Instruments. Delft, The Netherlands (1 990).
Further details of the crystal structure investigation are available on request
from the Director of the Cambridge Crystallographic Data Centre, 12 Union
Road. GB-Cambridge CB2lEZ (UK) on quoting the full journal citation.
[21] S. Matsugo. I. Saito in Orgunrc Peroxides (Ed: W. Ando), Wiley, Chichester,
1992.
(221 J. A. Kampmeier, R. R. Geer. A. J. Meskin, R. M. DSilva, J. Am. Chem. SOC.
1966, 88, 1257; J. P. Lorand, P. D. Bartlett. ibrd 1966, 88, 3294; J.-J. L. Fu,
W. G. Bentrude, ibid. 1972, 94, 7710.
Bis(2,6-dimethoxyphenyl)phenylniethanol(1 b-OH): A solution of 1.3-dimethoxyphenyllithium was prepared by addition of 2.5 M nBuLi (34.8 mL, 86.9 mmol) in
n-hexane to a solution of 1,3-dimethoxybenrene (10 g, 72.4 mmol) in anhydrous
diethyl ether at -78 'C. The mixture was stirred at room temperature under argon
for 48 h. Methylbenroate (3.13 g. 23.0 mmol) in benzene (20 mL) was added. and
the reaction solution was heated at reflux for 3 days under argon. The reaction
mixture was poured into 200 mL of water, and the organic layer was dried and
concentrated to yield the methanol as an oil. The oil was crystallized in CH,CI, and
hexane.Mp104"C,46%yield. 'HNMR(CDC1,,299.95 MHz):b = 3.38(s,12H),
6.43 (s. 1 H), 6.54(d. J = 8 H r , 4 H ) , 7.11 (t. J = 8 Hz, 2H), 7.13 (m.1H). 7.21 (m.
2H), 7.46 (m.2H); "CC('HJNMR (CDCI,, 75.46MHz): 6 = 56.5, 79.5, 106.74,
125.37. 126.31, 126.50. 126.63. 127.28, 149.5, 158.5.
1 b+ BF,: A solution of 1b-OH (500 mg, 1.31 mmol) in 150 mL diethyl ether was
treated with 0.1 mL of 48% HBF,. The resulting crystalline blue precipitate was
filtered and dried to give the BF, salt of bis(2,6-dimethoxyphenyl)phenylmethyl
cation quantitatively. Mp 142-143°C. ' H N M R (CDCI,, 299.95 MHz): b = 3.54
(5. 12H). 6.63 (d. J = 8 Hz, 4H), 7.44 (m, 4 H ) ; 7.61 (m, 1 H), 7.79 (t. J = 8 Hz, 2H);
I 3 C / ' H } NMR (CDCI,, 75.46 MHz): 6 = 56.83, 105.36, 125.00, 129.09, 134.59.
137.02, 145.90. 163.79, 191.58.
1 b: Compound 1 b+ . BF; (200 g) was reduced by a 5 M CrCl, solution (20 mL,
prepared with CrCI, 6H,O and Zn/Hg in 10% HCI solution), extracted with
CH2CI,. washed with water. and dried with MgSO,. The solution was chromatographed over silica gel to give the radical (35 %, based on SQUID measurement (SQUID = Superconducting Quantum Interference Device), perf= 0.61 p g ) ;
m.p. 355-157'C.
6b: Solutions of 1 b were allowed to stand in air for 3 days. Red-orange crystals of
the peroxide precipitated during this time. Mp 121 "C; ' H N M R (CDCI,,
2 9 9 9 5 M H z ) : b = 3 . 4 0 ( ~ . 1 2 H ) , 3 . 5 8 ( d ,J=2Hz,12H),4.82(m.IH),5.54(m,
2 H ) . 6.12 (m. 2H). 6.44 (m. XH), 6.55 (m. ZH), 7.03 (t. J = 6Hz, 4H). 7.05 (m.
Akihiko Ishii, Toru Akazawa, Teruo Maruta,
1 HO, 7.11 (t. J = 6 Hz, 2H), 7.68(d, J = 6 Hz, 2H); ' T { ' H } NMR (CDCI,,
Juzo Nakayama,* Masamatsu Hoshino,
75.46 MHz): b = 55.94. 56.33. 103.94. 104.13, 106.47, 117.50. 124.71, 125.63,
and Motoo Shiro
125.85. 126.15. 127.07. 127.861, 127.99, 130.05, 147.20. 154.50, 158.43, 158.50; IR
(KBr): ? = 2992. 2936, 2832, 1586, 1472, 1430. 1288, 1252, 1110, 1030. 928, 780,
726cm-l.
The smallest cyclic disulfides, the dithiiranes, are of interest as
7b: Tris(2,6-dimethoxyphenyl)methyl (1c ) was prepared as described previously
isomers of thiocarbonyl S-sulfides (thiosulfines) and dithio[ l l ] . A pale orange solid (7c) precipitated from ether solutions that stood in air for
esters.['. 21 In dithiiranes the dihedral angle of 0" leads to signif3 days. The solid was washed with diethyl ether and recrystallized from THF.
icant repulsive lone pair-lone pair interactions in addition to
Mp > 300 C; correct C,H elemental analyses. 'HNMR (CDCI,, 299.95 MHz):
6 = 3 . 1 3 ( s . 12H). 3.52 (d, J = 2 H z . 24H), 5.02 (d, J = 8 H z . 4 H ) , 5.34 (t.
large angle strains,[31and therefore, although several dithiiranes
J = 8 Hr. 2H), 6.39 (d, J = 8 Hz. XH), 6.99 (d, J = 8 Hz, 4H); satisfactory C.H
have been recognized as elusive intermediates, no isolable exanalysis; IR (KBr): i. = 2928,2828,1654,1611,1584.1470.1431.1382, 1298,1249.
1219. 1108, 912, 742cm-'.
[*I Prof. Dr. J. Nakayama. Dr. A. Ishii, T. Akazawa. T. Maruta,
Received: October 11, 1993 [Z 6408 IE]
Prof. Dr. M. Hoshino
German version: Angrw. Chem. 1994, 106, 826
Department of Chemistry
Faculty of Science. Saitama University
[I] a) J. Schmidlin, Ber. Dtsch. Chem. Ges. 1908,41, 2471. b) This equilibrium was
Urawa, Saitama 338 (Japan)
first proposed by B. Fliirscheim. J. Pruki. Chem. 1905, 71, 497; Eer. Dtsch.
Telefax: Int. code + (48)858-3698
Chwn. Ges. 1908, 4 f , 2746.
[2] M. Gomberg, Ber. Dlsch. Chem. Ges. 1900,33.3150; JT Am. Chem. Soc. 1900.
Dr. M. Shiro
22. 757.
Rigaku Corporation (Japan)
'
The First Isolable Dithiirane by Oxidation
of a Dithietane
Angeii-. Chem. h t . Ed. EngI. 1994. 33, No. 7
;g VCH Verlugsgesrlkhafi mhH. 0-69451 Weinheim, f994
0570-0833/94/0707-0777i% 10.00t.25/0
777
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