A structural model for the galactose oxidase active site which shows counteranion-dependent phenoxyl radical formation by disproportionation

Full text of DOI:10.1002/(SICI)1521-3773(20000502)39:9<1666::AID-ANIE1666>3.0.CO;2-O

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dron Lett. 1983, 24, 4391; e) L. Liu, R. S. Tanke, M. J.
Miller, J. Org. Chem. 1986, 51, 5332.
[8] G. I. Birnbaum, S. R. Hall, J. Am. Chem. Soc. 1976, 98,
1926.
[9] B. W. Bycroft, T. J. King, J. Chem. Soc. Perkin Trans. 1
1976, 1996. Professor Bycroft informed us after the
appearance of his paper that the configuration at C-18
was R rather than S and we confirmed this by inserting the
atomic coordinates obtained by the British group into the
SHELXTL program, version 5, which showed that both
hydroxy groups at C-18and C-20 were indeed syn as
shown in 1.
Me
O
N
O
H
HO2C
Me
O
S
8
N
O
O
O
O
H
H
O
S
6
Mes
O
N
8
H2N
O
R
HOBt, EDCI, DMF
(78%)
14
CO2Allyl
O
O
18 R = OAllyl
a
Mes
19 R = NHAllyl
Me
O
[10] Another version of this lactone 5 was prepared 20 years
PCy3
Ru
O
H
O
Cl
Cl
ago by
a slightly different procedure. However the
8
N
Ph
S
H
benzamide and methyl ester in 5 proved to be worthless
in proceeding with the synthesis of griseoviridin. A. I.
Meyers, R. A. Amos, J. Am. Chem. Soc. 1980, 102, 870.
[11] H. W. Yang, D. Romo, J. Org. Chem. 1998, 63, 1344.
[12] D. B. Dess, J. C. Martin, J. Am. Chem. Soc. 1991, 113, 7277.
[13] T. Kurihara, Y. Nakajima, O. Mitsunobu, Tetrahedron
Lett. 1976, 2455.
PCy3
b
(_) griseoviridin 1
O
N
PhCH3, 100 °C
0.001M
O
NH
(37-42%)
O
O
20
Mes
[14] Confirmation of complete inversion at C-5 was provided
by comparison of the 1H NMR spectrum with that of the
C-Me diastereomeric lactone prepared by cyclization
under Yamamoto lactonization conditions; see: K. Ishi-
hara, M. Kubota, A. Kurihara, H. Yamamoto, J. Org.
Chem. 1996, 61, 4560.
Scheme 3. Synthesis of griseoviridin (1). a) [Pd(PPh3)4], pyrrolidine; allyl amine, HOBt,
EDCI, DMF, 82%; b) PPTS, acetone/H2O, 68%. HOBt ˆ 1-hydroxy-1H-benzotriazole,
EDCI ˆ N'-(3-dimethylaminopropyl)-N-ethylcarbodiimide, PPTS ˆ pyridinium-p-tol-
uenesulfonate.
[15] Q. Dong, C. E. Anderson, M. A. Ciufolini, Tetrahedron Lett. 1995, 36,
5681.
[16] P. E. Sonnet, Tetrahedron 1980, 36, 557, and references therein.
[17] a) W. König, R. Geiger, Chem. Ber. 1973, 106, 3626; b) J. C. Sheehan,
J. Preston, P. A. Cruickshank, J. Am. Chem. Soc. 1965, 87, 2492.
[18] R. Deziel, Tetrahedron Lett. 1987, 28, 4371.
[19] R. H. Grubbs, S. Chang, Tetrahedron 1998, 54, 4413, and references
therein.
[20] We thank Professor Bycroft for sending us a sample of 1 (over 25 years
old) which arrived totally intact, and gave a very clean 13C and
1H NMR spectrum.
eomer in 68% yield. The entire sequence was performed in 24
linear steps from (S)-malic acid. The material thus obtained
was shown to be identical in all respects to natural griseovir-
idin[20] (1H, 13C NMR, [a]D, etc.).
The sequence leading to C-8 epi-griseoviridin[21] was
performed in exactly the same manner and led to a product,
in comparable yields, that was distinctly different from natural
griseoviridin in its spectroscopic properties. Attempts to
ascertain whether ene ± thiol lactone 5 could be interconvert-
ed to its C-8epimer proved fruitless due to decomposition
when strong bases were employed. Further, attempts to
incorporate deuterium into the C-8position of 5 also failed. In
summary, griseoviridin and its C-8epimer have been synthe-
sized for the first time employing a novel ring-closing
metathesis which involved a highly diasteroselective triene
to diene macrocyclic ring formation.
[21] A sample of the heretofore unknown C-8 epi-griseoviridin has been
submitted for antibacterial screening (Aventis) and found to be only
very poorly active (courtesy of Dr.S. Dutka-Malen).
A Structural Model for the Galactose Oxidase
Active Site which Shows Counteranion-
Dependent Phenoxyl Radical Formation by
Disproportionation**
Received: January 3, 2000 [Z14501]
[1] a) ªThe Streptogramin Family of Antibioticsº, D. Vasquez in Anti-
biotics III (Eds.: J. W. Corcoran, F. H. Hahn), Springer, New York,
1975; b) for recent antibacterial activity see: R. C. Möllering, P. K.
Linden, J. Reinhardt, E. Blumberg, G. Bompart, G. H. Talbot, J.
Antimicrob. Chemother. 1999, 44, 251.
[2] F. Tavares, J. P. Lawson, A. I. Meyers, J. Am. Chem. Soc. 1996, 118,
3303.
[3] R. H. Schlessinger, Y. Li, J. Am. Chem. Soc. 1996, 118, 3301.
[4] Etamycin (2) has been synthesized: J. C. Sheehan, S. L. Ledis, J. Am.
Chem. Soc. 1973, 95, 875.
[5] Denver Rocky Mountain News, Sept. 22, 1999: ªFDA approved
Synercid to treat vancomycin-resistant enterococcal and Staph
infectionsº. Synercid is a trade name for the combination of Group
A and B streptogramins manufactured by Rhone-Poulenc Rorer.
[6] D. A. Entwistle, S. I. Jordan, J. Montgomery, G. Pattenden, J. Chem.
Soc. Perkin Trans. 1 1996, 1315.
[7] a) A. I. Meyers, J. P. Lawson, D. G. Walker, R. J. Linderman, J. Org.
Chem. 1986, 51, 5111; b) P. Helquist, M. Bergdahl, R. Hett, A. R.
Gangloff, M. Demillequand, M. Cottard, M. M. Mader, T. Friebe, J.
Iqbal, Y. Wu, B. Škermark, T. Rein, N. Kann, Pure Appl. Chem. 1994,
66, 2063; c) R. H. Schlessinger, E. J. Iwanowicz, J. P. Springer,
Tetrahedron Lett. 1988, 29, 1489; d) R. D. Wood, B. Ganem, Tetrahe-
Yuichi Shimazaki, Stefan Huth, Akira Odani, and
Osamu Yamauchi*
Galactose oxidase (GO) contains one copper ion at its
active site and performs a two-electron oxidation of primary
alcohols to aldehydes, coupled with a reduction of O2 to
[*] Prof. Dr. O. Yamauchi, Y. Shimazaki, S. Huth,[‡] Dr. A. Odani
Department of Chemistry
Graduate School of Science and Research Center for Materials
Science
Nagoya University, Nagoya 464-8602 (Japan)
Fax : (‡81)52-789-2953
E-mail: b42215a@nucc.cc.nagoya-u.ac.jp
‡
[ ] On leave of absence from the University of Bremen
[**] This work was supported by Grants-in-Aid for Scientific Research
(No. 09304062 and 0149219 (Priority Areas) to O.Y. and No.
07CE2004(COE) to A.O.) from the Ministry of Education, Science,
Sports, and Culture of Japan, for which we express our thanks.
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H2O2.[1] Structural studies of the inactive form of GO have
revealed that there exist two distinct tyrosine residues in the
active site, one of which is a cysteine-modified phenol moiety
of tyrosine272 (Y272) coordinated to the copper center as an
equatorial ligand, while the other is a phenol group of
tyrosine495 (Y495) bound at an apical position.[2] The CuII ion
and a phenoxyl radical together effect the two-electron
oxidation reaction.[3] The proposed mechanism of catalysis
involves a cycle of the CuI ± phenol and CuII ± phenoxyl radical
states; no CuII ± phenolate form has been detected during
catalysis.[1, 2, 4]
structure analysis revealed that 1 contains two phenol
moieties coordinated to CuII in different ways (Figure 1),
and the unit cell consists of two crystallographically inde-
pendent complex molecules.[9] The CuII center is in a distorted
Recent synthetic studies afforded well-characterized mono-
nuclear CuII ± phenoxyl radical species, which provided fur-
ther insights into the reactivity of the GO active site.[5]
Tripodal ligands introduced by Karlin[6] have been developed
for use as GO model ligands in a number of studies.[5c, f, h, 7, 8]
Model complexes of ligands with two or more phenol moieties
have also been synthesized by several groups.[5b, d, e, f, k±m]
However, modeling of the coordination structure and roles
of the two coordinated phenol moieties with monomeric CuII
complexes has not yet been fully achieved, and dimerization
of the complexes often occurs.[5f,h, 7, 8] We report here the
synthesis and characterization of a novel mononuclear CuII
complex of a tetradentate tripodal ligand, which is similar to
that prepared by Pierre et al.,[5f] with two phenol moieties and
two tert-butyl groups introduced. The coordination structure
has been found to closely resemble that of the inactive GO
form.[2] Preliminary studies showed that, while Cu(OAc)2
gives a stable GO-mimicking complex with two phenol
moieties coordinated, the CuCl2 and Cu(ClO4)2 ligand sys-
tems react differently and the latter spontaneously gives the
phenoxyl radical species by disproportionation.
Figure 1. ORTEP view of [Cu(HL)(OAc)] 1 (drawn with the thermal
ellipsoids at the 30% probability level) and atomic labeling scheme.
À
À
Selected bond lengths [Š] and angles [8]: Cu(1) N(1) 2.001(6), Cu(1) N(2)
À
À
À
2.043(5), Cu(1) O(1) 1.883(4), Cu(1) O(2) 2.418(5), Cu(1) O(3) 1.957(5);
N(1)-Cu(1)-N(2) 83.2(2), N(1)-Cu(1)-O(1) 159.6(2), N(1)-Cu(1)-O(2)
90.5(2), N(2)-Cu(1)-O(2) 86.6(2), N(1)-Cu(1)-O(3) 93.1(2), O(1)-Cu(1)-
O(2) 109.6(2), O(1)-Cu(1)-O(3) 88.5(2).
square-pyramidal geometry formed by a phenolate oxygen, a
pyridine nitrogen, a tertiary amine nitrogen, and an acetate
oxygen in the coordination plane with a protonated phenol
À
oxygen at an axial position with an average Cu O bond length
of 2.40 Š.
N-(2-pyridylmethyl)-N,N-bis(2'-hydroxy-3',5'-di-tert-butyl-
benzyl)amine (H2L) was treated with Cu(OAc)2 ´ 2H2O in
CH2Cl2/CH3CN in air at room temperature to give [Cu(HL)-
(OAc)] ´ H2O (1) as brown crystals (Scheme 1). X-ray crystal
The brown solution of 1 exhibited the phenolate ± CuII
charge transfer band at 470 nm (e ˆ 1300), which disappeared
upon oxidation with CeIV in CH2Cl2/CH3CN at low temper-
ature (À408C), but formation of the phe-
noxyl radical could not be detected. Decom-
position products 2 and 3 were isolated from
the reaction mixture, both in 15% yield
(Scheme 1). Cyclic voltammetry in CH2Cl2
with tetrabutylammonium perchlorate re-
oxidation by CeIV
aqueous NH3 (– Cu ion)
Cu(OAc)2•2H2O
1
vealed an irreversible oxidation at 0.62 V
O
– Cu ion
against Ag/AgCl (scan rate ˆ 100 mVsÀ1).
(CuII–phenoxyl radical)
Cu(ClO4)2•6H2O
N
OH
2
N
CH2Cl2/CH3CN
Complex 1 was found to be inactive for
[CuI(CH3CN)4]ClO4
–40 °C
oxidation of ethanol.
OH
OH
On the other hand, Cu(ClO4)2 ´ 6H2O
H
N
underwent a reaction with H2L in CH2Cl2/
CH3CN, to rapidly form a deep green color.
After exposure to air at room temperature,
the deep green reaction mixture turned
colorless, and yielded colorless crystals of
[Cu(CH3CN)4]ClO4 (yield of the first crop,
35%; subsequent small crops were also
obtained). The deep green intermediate
solution at À408C exhibited an absorption
band centered at 403 nm (e ˆ 2000) with a
shoulder and at 654 nm (e ˆ 400); no X-band
EPR signals were observed, which is consis-
N
H2L
OH
3
H
N
N
– Cu ion
5
4
O
HL'
– Cu ion
OH
CuCl2•2H2O
Scheme 1. Reaction scheme for CuII ± H2L system which shows the dependence on the
counterion.
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tent with a CuII ± phenoxyl radical species as these are known
to give typical absorption peaks, for example, at 410 (e ˆ
4000), 422 (e ˆ 3800), and 672 nm (e ˆ 1000).[5d] The radical
species was also detected under an inert gas atmosphere, and
colorless crystals of [Cu(CH3CN)4]ClO4 were isolated, show-
ing that the radical formation is not due to oxidation by
dioxygen. The deep green reaction intermediate was short
lived relative to some of the reported oxidized species,[5]
decaying by a first order process at À208C with k ˆ (9.3 Æ
0.2) Â 10À4 sÀ1 (UV± Visible monitoring). No such reactions
were observed for a solution containing methanol, which gave
the dimeric complex Cu2L2 as brown powder upon addition of
triethylamine.[5f] Decomposition products 2 and 3 (yields less
than 10%) were also detected in the colorless reaction
mixture of the Cu(ClO4)2 ± H2L system (Scheme 1). As they
are identical with those from complex 1, we may infer that
similar reactions have occurred in both systems.
Figure 3. ORTEP view of [Cu(HL')Cl2]
ellipsoids at the 30% probability level) and atomic labeling scheme.
Selected bond lengths [Š] and angles [8]: Cu N(1) 2.002(8), Cu N(2)
5 (drawn with the thermal
À
À
À
À
2.024(8), Cu Cl(1) 2.266(3), Cu Cl(2) 2.268(3); N(1)-Cu-N(2) 80.2(3),
N(1)-Cu-Cl(1) 96.2(3), N(1)-Cu-Cl(2) 158.0(3), N(2)-Cu-Cl(1) 176.2(2),
N(2)-Cu-Cl(2) 89.1(2), Cl(1)-Cu-Cl(2) 94.0(1).
When CuCl2 ´ 2H2O was used in place of Cu(ClO4)2 ´ 6H2O,
it underwent a reaction with H2L in CH2Cl2/CH3CN/hexane in
air to give [Cu(H2L)Cl2] (4) as green crystals, where the CuII
ion binds two nitrogen atoms and two chloride ions in the
coordination plane and the two phenol hydroxyl groups are
place by rapid dimer formation from 4 where the phenol
moieties are unbound or only weakly bound.
In conclusion, we obtained a new GO model CuII complex 1
of a tripodal ligand H2L, where the two side-chain phenol
moieties coordinated at an equatorial and an axial position in
the phenolate and the phenol form, respectively. Different
counteranions of the metal sources not only caused a large
structural difference in the complexes relative to that
reported earlier[8] but also affected the reactivity of the
À
protonated, one is also weakly coordinated (Cu O(1)
2.677(7) Š; Figure 2). Addition of triethylamine to 4 afforded
complexes, which increases as the order of anion basicity
À [11]
decreases: CH3COOÀ > ClÀ > ClO4 .
In the Cu(ClO4)2 ±
H2L system, spontaneous formation of a phenoxyl radical
species and [Cu(CH3CN)4]ClO4 due to disproportionation has
been observed. To the best of our knowledge, this is the first
observation of CuII ± phenoxyl radical formation by dispro-
portionation of CuII complexes.
Experimental Section
Figure 2. ORTEP view of [Cu(H2L)Cl2]
ellipsoids at the 30% probability level) and atomic labeling scheme.
Selected bond lengths [Š] and angles [8]: Cu N(1) 1.955(9), Cu N(2)
4 (drawn with the thermal
Synthesis of N-(2-pyridylmethyl)-N,N-bis(2'-hydroxy-3',5'-di-tert-butylben-
zyl)amine (H2L): 2,4-di-tert-butylphenol (4.12 g, 20 mmol) and paraform-
aldehyde (0.60 g, 20 mmol) were added to a solution of 2-pyridylmethyl-
amine (1.08g, 10 mmol) in ethanol (100 mL). The reaction mixture was
refluxed for two days to give a white powder which, after isolation, was
recrystallized from ethyl acetate to yield 2.01 g (56.3%). 1H NMR
(300 MHz, CDCl3): d ˆ 1.28(s, 18H; (CH 3)3C), 1.40 (s, 18H; (CH3)3C),
3.80 (s, 4H; phenol-CH2), 3.84 (s, 2H; py-CH2), 6.93 (d, 2H; phenol-H),
7.13 (d, 1H; py-H), 7.22 (d, 2H; phenol-H), 7.27 (m, 1H; py-H), 7.69 (td,
1H; py-H), 8.69 (d, 1H; py-H), 10.55 (br s, 2H; phenol-OH).
À
À
À
À
À
2.099(7), Cu Cl(1) 2.254(4), Cu Cl(2) 2.230(3), Cu O(1) 2.677(7); N(1)-
Cu-N(2) 82.3(5), N(1)-Cu-Cl(1) 94.3(4), Cl(1)-Cu-Cl(2) 93.7(2), N(1)-Cu-
O(1) 80.5(3), N(2)-Cu-O(1) 87.5(3).
the same dimeric complex as obtained from the Cu(ClO4)2 ±
H2L system.[5f] In connection with this, CuII ± tripodal ligand
complexes with an N3O chromophore have been isolated with
different anions.[8] By analogy with CuCl2, Cu(ClO4)2 most
probably initially forms a protonated complex such as 4, and
since the perchlorate ions can dissociate easily from CuII even
when they are bound, Cu2L2 should be more rapidly formed in
the Cu(ClO4)2 ± H2L system than from 4. Upon standing at
room temperature for a few weeks, 4 gave 2, 3, and complex 5
which coordinates a new product HL' (Figure 3); this was also
detected in a small amount in the Cu(ClO4)2 ± H2L system.
These results indicate that the CuII ± phenoxyl radical in this
system was produced together with [Cu(CH3CN)4]ClO4 as a
result of a disproportionation reaction,[10] which may take
Synthesis of 1: The complex was prepared from H2L and Cu(OAc)2 ´ 2H2O
in CH2Cl2/CH3CN (1:1) to give brown crystals. Elemental analysis (%)
calcd for C38H57N2O5Cu: C 66.59, H 8.38, N 4.09; found: C 66.13, H 8.450, N
4.08.
Synthesis of the dimer Cu2L2: H2L (0.545 g, 1.0 mmol) was dissolved in
CH2Cl2 (10 mL) which contained a few drops of triethylamine and was
added to a solution of Cu(ClO4)2 ´ 6H2O (0.370 g, 1.0 mmol) in methanol
(10 mL), which caused a brown powder to separate immediately. This was
collected and dried. Elemental analysis (%) calcd for C72H100N4O4Cu2: C
71.31, H 8.31, N 4.62; found: C 70.99; H 8.153; N 4.619.
Synthesis of 4: Small green crystals were obtained from a solution of H2L
and CuCl2 ´ 2H2O in CH2Cl2/CH3CN/hexane (1/1/1). Elemental analysis
(%) calcd for C36H52N2O2CuCl2: C 63.66, H 7.72, N 4.12; found: C 63.29, H
7.596, N 4.07.
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Typical recovery of reaction products:[12] compound 4 (0.350 g, 0.514 mmol)
was dissolved in CH3OH/CH3CN (1:1) and kept standing for a few weeks at
room temperature. The green crystals which separated from the reaction
mixture were collected, and the brown filtrate was evaporated in vacuo.
The residue was dissolved in concentrated aqueous NH3 (10 mL) and
extracted with CHCl3 (4 Â 10 mL). The combined organic fractions were
washed with concentrated aqueous NaCl (3 Â 10 mL), dried over Na2SO4,
filtered, and concentrated in vacuo to leave a brown oil. Compounds 2 and
3 were separated by column chromatography, and their structures and
[8] a) H. Adams, N. A. Bailey, D. E. Fenton, Q.-Y. He, M. Ohba, H.
Okawa, Inorg. Chim. Acta 1994, 215, 1; b) H. Adams, N. A. Bailey,
I. K. Campbell, D. E. Fenton, Q.-Y. He, J. Chem. Soc. Dalton Trans.
1996, 2233.
[9] X-ray crystal structure determination: The X-ray diffraction data were
collected at 295 K with a Rigaku AFC-5R four-circle diffractometer
using graphite-monochromated CuKa radiation (l ˆ 1.54178Š). Crys-
tal data for 1: Formula C76H108N4O9Cu2, Mw ˆ 1348.80, crystal size:
0.3  0.1  0.1 mm, monoclinic, space group P21/n, a ˆ 26.782(4), b ˆ
10.672(2), c ˆ 26.819(3) Š, b ˆ 94.33(1)8, Vˆ 7643(2) Š3, Z ˆ 4,
1
yields were determined by H NMR. The structure of ligand HL' in 5 was
determined by X-ray analysis of 5 and by 1H NMR after removal of CuII as
1calcd ˆ 1.352g cmÀ3
,
m ˆ 12.39 cmÀ1
F(000) ˆ 3112.00, 13682 inde-
,
1
described above. Compound 2: Yield, 15%; H NMR (300 MHz, CDCl3):
pendent reflections, 8230 reflections used, 821 parameters, R ˆ 0.074,
Rw ˆ 0.085 (I > 2.00s(I)). In the asymmetric unit there were two
crystallographically independent complex molecules, which have very
similar structures and may be regarded as mirror images arising from
the coordination of the tertiary amine nitrogen to CuII. Crystal data
for 4: Formula C37H56N2O3Cl2Cu, Mw ˆ 711.31, crystal size: 0.17 Â
d ˆ 1.33 (s, 9H; (CH3)3C), 1.43 (s, 9H; (CH3)3C), 7.34 (d, 1H; phenol-H),
7.59 (d, 1H; phenol-H), 9.87 (s, 1H; phenol-OH), 11.64 (s, 1H; CHO).
Compound 3: Yield, 15%; 1H NMR (300 MHz, CDCl3): d ˆ 1.28(s, 9H;
(CH3)3C), 1.43 (s, 9H; (CH3)3C), 3.93 (s, 2H; CH2), 3.98(s, 2H; CH 2), 6.84
(d, 2H; phenol-H), 7.2 (m, 3H; py-H, phenol-H), 7.66 (td, 1H; py-H), 8.58
(d, 1H; py-H). Compound 5: Yield, 12%; elemental analysis (%) calcd for
C35H50N2O2CuCl2: C 63.19, H 7.58, N 4.21; found: C 63.07, H 7.532, N 4.27.
HL': 1H NMR (300 MHz, CDCl3): d ˆ 1.11 (s, 9H, (CH3)3C), 1.33 (s, 9H,
(CH3)3C), 1.37 (s, 9H, (CH3)3C), 1.47 (s, 9H, (CH3)3C), 3.47 (q, 2H; CH2),
3.73 (q, 2H; CH2), 6.27 (d, 1H; phenol-H), 6.90 (d, 1H; phenol-H), 7.14
(dd, 1H; py-H), 7.16 (d, 1H; phenol-H), 7.19 (d, 1H; py-H), 7.37 (d, 1H;
phenol-H), 7.60 (td, 1H; py-H), 8.52 (d, 1H; py-H).
Å
0.10  0.06 mm, triclinic, space group P1, a ˆ 13.865(4), b ˆ
16.048(5), c ˆ 10.378(5) Š,
a ˆ 98.69(5),
b ˆ 104.67(4), g ˆ
112.64(2)8, Vˆ 1980(1) Š3, Z ˆ 2, 1calcd ˆ 1.193 gcmÀ3, m ˆ 22.80 cmÀ1
,
F(000) ˆ 758.00, 5791 independent reflections, 5791 reflections used,
407 parameters, R ˆ 0.083, Rw ˆ 0.128( I > 2.00s(I)). Crystal data for
5: Formula C35H50N2O2Cl2Cu, Mw ˆ 665.24, crystal size: 0.20  0.15 Â
0.03 mm, monoclinic, space group P21/a, a ˆ 18.054(4), b ˆ 12.712(7),
c ˆ 18.314(4) Š, b ˆ 116.00(1)8, Vˆ 3783(2) Š3, Z ˆ 4, 1calcd
ˆ
Received: November 11, 1999 [Z14258]
1.168gcm À3, m ˆ 23.35 cmÀ1, F(000) ˆ 2256.00, 5357 independent re-
flections, 4926 reflections used, 380 parameters, R ˆ 0.069, Rw ˆ 0.107
(I > 2.00s(I)). Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publica-
tion nos. CCDC-136595, -136596, and -136821. Copies of the data can
be obtained free of charge on application to CCDC, 12 Union Road,
Cambridge CB21EZ, UK (fax: (‡44)1223-336-033; e-mail: deposit@
ccdc.cam.ac.uk)..
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Reaction of Organic Selenocyanates with
Hydroxides: The One-Pot Synthesis of Dialkyl
Diselenides from Alkyl Bromides
Alain Krief,* Willy Dumont, and Cathy Delmotte
Â
Chem. 1997, 2, 444; f) D. Zurita, I. Gautier-Luneau, S. Menage, J.-L.
Pierre, E. Saint-Aman, J. Biol. Inorg. Chem. 1997, 2, 46; g) Y. Wang,
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Jr., W. B. Tolman, Chem. Commun. 1998, 2521; k) P. Chaudhuri, M.
Hess, U. Flörke, K. Wieghardt, Angew. Chem. 1998, 110, 2340; Angew.
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Dedicated to Professor Bernd Giese
on the occasion of his 60th birthday
Since the beginning of organoselenium chemistry, organo-
selenocyanates have occupied a privileged position.[1] They
are easily prepared, are stable to atmospheric conditions, and
have widely contributed to the use of organoselenium
compounds in synthesis due to their exceptional versatility.[1]
They react with a large variety of compounds, producing
chemoselectively, in a single step and in almost quantitative
[*] Prof. Dr. A. Krief, Dr. W. Dumont, Dipl.-Chem. C. Delmotte
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1987, 26, 147.
Á
Laboratoire de Chimie Organique de Synthese
Â
Departement de Chimie
Â
Facultes Universitaires Notre-Dame de la Paix
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ayanan, J. Chem. Soc. Dalton Trans. 1992, 3563; b) M. Vaidyanathan,
R. Viswanathan, M. Palaniandavar, T. Balasubramanian, P. Prabha-
haran, T. P. Muthiah, Inorg. Chem. 1998, 37, 6418.
61 rue de Bruxelles, 5000 Namur (Belgium)
Fax : (‡32)81-724536
E-mail: alain.krief@fundp.ac.be
Angew. Chem. Int. Ed. 2000, 39, No. 9
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