Substrate-binding ligand approach in chemical modeling of copper- containing monooxygenases, 1. - Intramolecular stereoselective oxygen atom insertion into a non-activated C-H bond

Article abstract of DOI:10.1002/(SICI)1099-0682(200002)2000:2<393::AID-EJIC393>3.0.CO;2-2

We describe the reactivity of new copper AlkylPY2 type complexes which react with dioxygen and thus hydroxylate an aliphatic C-H bond of the ligand in the same manner as copper-containing monooxygenases.

Full text of DOI:10.1002/(SICI)1099-0682(200002)2000:2<393::AID-EJIC393>3.0.CO;2-2

FULL PAPER
Substrate-Binding Ligand Approach in Chemical Modeling of
Copper-Containing Monooxygenases, 1
Intramolecular Stereoselective Oxygen Atom Insertion into a Non-Activated
C–H Bond
[a]
[a]
[b]
[a]
´
Ingrid Blain, Michel Giorgi, Innocenzo De Riggi, and Marius Reglier*
Keywords: Copper / Oxygenase / Copper–oxygen radical species / RPY2 ligand / Oxygenation
We describe the reactivity of new copper AlkylPY2 type
complexes which react with dioxygen and thus hydroxylate
an aliphatic C–H bond of the ligand in the same manner as
copper-containing monooxygenases.
a propyl or cyclopentyl group as the substrate in order to
find out if copper-oxygen species are capable of inserting
an oxygen atom into a nonactivated CϪH bond.
Introduction
Copper-containing monooxygenases[1] are involved in
important biological reactions and copper-dioxygen chem-
istry has been the subject of important recent investi-
gations.[2] It has been shown that copper(I) coordinated to
tridentate ligands {HB(3,5-iPr2pz)3,[3] RPY2,[4,5] P(2,4-
[6]
iPr2im)3 and iPr3tacn[7] leads to [CuII2(µ-η2:η2-O2)]2ϩ
species upon reaction with dioxygen. More recently, Tol-
man et al.[8] reported that these species can exist in equilib-
rium with a bis(µ-oxo)dicopper species in a formal
[CuIII2(µ-O)2]2ϩ oxidation state. Whereas the structure of
these copper-dioxygen adducts is now well documented, few
examples of exogenous substrate oxidation mediated by
these species are known.[4] In some cases, these peroxo spec-
ies are capable of inserting an oxygen atom into a CϪH
bond of the ligand.[5Ϫ7,9,10] Taking advantage of this be-
havior, we described in previous papers,[10] the substrate-
binding ligand approach, which involves the study of copper
complexes derived from RPY2-type ligands. In these com-
pounds a substrate is covalently bound to the ligandЈs ter-
tiary amino group in such a way that an intramolecular
oxygen-atom transfer from the copper center to the ligand
is favored. The chemio-, regio- and stereoselectivities of the
oxygen atom transfer, as revealed by the structure of the
hydroxylated ligands, are used to gain more information on Scheme 1. Substrate-binding ligand approach
the nature of the hydroxylating species and the exact oxi-
dation mechanism. When using such complexes, benzylic
hydroxylation (DBH functional model)[5,10c] and hydroxyl-
ation at the α-position of the amido group (PHM func-
tional model)[10a] were described. Herein, we report the re-
actions of a new RPY2 ligand in which we chose to attach
Results and Discussion
The new RPY2 ligands were synthesized from simple or-
ganic reactions. Thus, Michael addition of primary amines
to freshly distilled 2-vinyl pyridine in a methanol/acetic acid
mixture yielded the ligands nPrPY2 and cPtPY2. The cop-
per(II) complexes [nPrPY2]Cu(OTf)2 and [cPtPY2]Cu-
(OTf)2 (OTf ϭ OSO2CF3) were obtained in methanol in
nearly quantitative yields by complexation of the corre-
sponding ligands with Cu(OTf)2. Recrystallization from di-
chloromethane using the diethyl ether vapor diffusion tech-
nique afforded blue crystals of [nPrPY2]Cu(OTf)2 which
were suitable for an X-ray diffraction analysis (Table 1,
Figure 1).
[a]
Chimie, Biologie et Radicaux Libres, UMR-CNRS 6517, case
´
´
432, Universites d’Aix-Marseille 1 et 3, Faculte des Sciences et
´ ˆ
Techniques de Saint Jerome,
av. Escadrille Normandie-Niemen, F-13397 Marseille Cedex 20,
France
Fax: (internat.) ϩ 33-4/9198-3208
E-mail: marius.reglier@lbs.u-3mrs.fr
[b]
´
´
ENSSPICAM, Universite dЈAix-Marseille 3, Faculte des Scien-
´ ˆ
ces et Techniques de Saint Jerome,
av. Escadrille Normandie-Niemen, F-13397 Marseille Cedex
20, France
Eur. J. Inorg. Chem. 2000, 393Ϫ398
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
1434Ϫ1948/00/0202Ϫ393 $ 17.50ϩ.50/0
393

´
I. Blain, M. Giorgi, I. De Riggi, M. Reglier
FULL PAPER
Table 1. Crystallographic data for [nPrPY2]Cu(OTf)2·2H2O
Crystal data
Formula
C19H27CuF6N3O8S2
667.09
Mr
Crystal system
Space group
monoclinic
P21/n
˚
a [A]
8.899(1)
13.726(1)
22.980(1)
90.000(1)
100.598(1)
90.000(1)
2759.1(6)
1.62
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
3
˚
V [A ]
Dcalc [g cmϪ3
Z
]
4
F(000) [e]
1180
µ (Mo-Kα) [Ϫ1
]
10.299
Data collection
T [K]
298
Scan mode
␾ scans
Scan width [°]
2θmax [°]
2
50Ϫ82
5455
5265
3321
none
none
Measured refl.
Unique refl.
Refl. used for ref.
Absorption correction
Extinction correction
Structure refinement
Ref. parameters
H atoms
Scheme 2
418
included not refined
0.047
R
Rw
0.054
2
w
1/[σ2F0 ϩ 0.03F0
0.0653
]
(shift/e.s.d.)max
Goodness of fit
1.783
0.55/ Ϫ0.59
Ϫ3
˚
∆ρfin(max/min) [eA
]
The copper complex [nPrPY2]CuPF6, was prepared in
situ by interaction (under argon) of the corresponding li-
gand nPrPY2 with 1 equiv. of (CH3CN)4CuPF6 in degassed
dichloromethane. When it was placed in a dioxygen atmos-
phere the clear yellow solution rapidly turned green and a
copper(II) complex was obtained. Demetallation with 35%
aqueous ammonia and analysis of the organic products
indicated the complete recovery of the starting ligand
nPrPY2 with no products resulting from an oxygen-atom
transfer to the ligand. More interesting were the results ob-
tained by treatment of [nPrPY2]Cu(OTf)2 with 2 equiv. of
benzoin/NEt3 in dichloromethane at 25°C. Under argon,
reduction to a copper(I) state by 2 equiv. of benzoin/NEt3
occurred in less than two hours. After exposure to a dioxy-
gen atmosphere for 18 hours and demetallation with 35%
aqueous ammonia, analysis of the organic products indi-
cated the presence of compounds 1a, 2a and AllPY2 in ad-
Figure 1. Perspective view of the copper(II) complex [nPrPY2]-
Cu(OTf)2 emphasizing the central coordination sphere; selected
˚
bond distances (A): CuϪOw(1), 2.224 (3), CuϪOw(2), 2.045 (3),
CuϪN(1), 2.088 (3), CuϪN(2), 1.994 (3), CuϪN(3), 1.990 (4);
bond angles (°): Ow(1)ϪCuϪOw(2), 102.8 (1), Ow(1)ϪCuϪN(2),
86.9 (2), Ow(1)ϪCuϪN(1), 106.8 (2), Ow(1)ϪCuϪN(3), 93.5 (2),
Ow(2)ϪCuϪN(2), 87.8 (2), Ow(2)ϪCuϪN(1), 150.2 (2), Ow(2)Ϫ-
CuϪN(3), 86.4 (2), N(2)ϪCuϪN(1), 96.4 (2), N(2)ϪCuϪN(3),
174.1 (2), N(1)ϪCuϪN(3), 89.1 (2).
dition to recovered ligand nPrPY2 and small amounts of 4.75 corresponding to NϪCH2ϪCHOHϪpyr. Compound
secondary amine PY2 resulting from an N-dealkylation re- 2a as revealed by NMR analysis and confirmed by com-
action (Table 2, entry 2).[11] A thorough analysis of the parison with an authentic sample was the result of a β-
spectral data indicated that the main product 1a was the hydroxylation of the n-propyl group.[12]
result of hydroxylation at the benzylic position of one pyri-
In order to study the stereoselectivity of the oxygen-atom
dine ring. This is clearly evident from the 13C NMR spectra transfer to the alkyl part of the ligand, we then studied the
which show the splitting of all pyridine signals and the ap- reactivity of cPtPY2-derived copper complexes. As already
pearance of two new signals at δ ϭ 61.5 and 70.8, attribu- mentioned for [nPrPY2]CuPF6, we did not observe any hy-
table to the NϪCH2ϪCHOHϪpyr sequence, and from the droxylation products by reaction of [cPtPY2]CuPF6, pre-
1H NMR spectra which show a doublet of doublets at δ ϭ pared in situ, with dioxygen. However two equiv. of
394
Eur. J. Inorg. Chem. 2000, 393Ϫ398

Substrate-Binding Ligand Approach in Chemical Modeling of Copper-Containing Monooxygenases, 1
Table 2. Reactions of [RPY2]Cu(OTf)2 complexes with O2/Benzoin/NEt3 in CH2Cl2
FULL PAPER
Entries
Ligands
Ratios
Cu/Benzoin/NEt3
Product Distributions[a]
1
2
3
4
5
nPrPY2
nPrPY2
nPrPY2
nPrPY2
cPtPY2
1/0/2
1/2/2
1/2/4
1/4/4
1/2/2
nPrPY2 (98%) ϩ PY2 (2%)
nPrPY2 (44%) ϩ 1a (37%) ϩ 2a (8%) ϩ AllPY2 (2%) ϩ PY2 (9%)
nPrPY2 (37%) ϩ 1a (36%) ϩ 2a (6%) ϩ AllPY2 (3%) ϩ PY2 (18%)
1a (64%) ϩ 2a (10%) ϩ AllPY2 (6%) ϩ PY2 (12%)
cPtPY2 (35%) ϩ 1b (42%) ϩ 2b (13%) ϩ PY2 (5%)
[a]
Determined by HPLC (Ultrasphere C18 column, Beckmann) using H2O/CH3CN 90/10 containing 1% TFA as mobile phase, detection
at 270 nm using diode array detector.
benzoin/NEt3 in dichloromethane at 25°C transformed B to give a mixed valence species C which, as suggested by
[cPtPY2]Cu(OTf)2 into the hydroxylated compounds 1b Chan, could be active in transferring one oxygen atom to
and 2b (Table 2, entry 5). Compound 1b, which showed the the ligand to give {[HORPY2]CuII}2ϩ. This process is ac-
same spectroscopic features as 1a (13C NMR: splitting of companied by the formation of a copper(I) complex, which
all pyridine signals and appearance of two new signals at can participate again after reaction with dioxygen in a
δ ϭ 71 and 59; 1H NMR: dd at δ ϭ 4.76), was the result of monooxygenase-like cycle.[15] According to this mechanism,
a hydroxylation at a benzylic position. An NMR structural the transformation of copper(II) complexes [RPY2]Cu-
analysis of compound 2b revealed that it was the result of (OTf)2 in such a cycle needs two electrons (one equiv. of
a β-cis hydroxylation of the cyclopentane ring. The cis benzoin). We observed that the transformation of the orig-
stereochemistry could be assigned by a two dimensional inal copper(II) complexes into the observed products con-
NOESY sequence showing a Nuclear Overhauser Effect sumed a four-fold excess of benzoin (Table 2, entry 4).
(NOE) between protons H-2 and H-1.[13]
Benzoin is a strong reducing agent that can participate in a
In one of our previous papers the higher deuterium kine- second electron addition to C (and/or D) in a competitive
tic isotope effect observed for reaction of [IndPY2]CuPF6/ reaction to give a different copper(II) species which is unre-
O2 relative to that of [IndPY2]Cu(OTf)2/benzoin/NEt3/O2 active in the hydroxylation reaction (oxydase like cycle).
(11 vs. 7.6) was rationalized as being due to the occurrence The two competitive processes (oxydase vs. monooxygen-
of two different copper-oxygen intermediates.[10c] The ab- ase) may explain why the complete transformation of [RPY-
sence of Oxygen Atom Transfer to the Ligand (OATL) dur- 2]Cu(OTf)2 needs more than one equiv. of benzoin.
ing the reaction of [RPY2]CuPF6 with dioxygen confirms
The OATL mechanism needs some comments. Scheme 4
this suggestion. At this time it is difficult to provide any illustrates possible pathways whereby hydroxylation can oc-
evidence for the oxygenated copper species responsible for cur via the dimeric species C (or monomer D). The first
the hydroxylation. Nevertheless, on the basis of the ob- explanation for the formation of 1a or 1b is to consider that
served products we can formulate several hypotheses con- the electrophilic CuIII core in B (or C) increases the acidity
cerning the structure of the active oxygen species. Itho,[5] of the benzylic hydrogen of pyridine, thus facilitating the
and more recently Karlin,[4a] with [PhenPY2]CuPF6 and deprotonation with triethylamine (path d). This mechanism
[MePY2]CuPF6 complexes, respectively, have shown that can be dismissed as increasing the amount of triethylamine
such complexes lead to {[RPY2]CuII2(µ-η2:η2-O2)}2ϩ by did not increase the amount of 1a in the [nPrPY2]Cu-
oxygenation, and that a homolytic cleavage of the peroxy (OTf)2/Benzoin/O2 reaction (Table 2, entry 3). From our re-
bond occurs (at least partially) to give, in the first step of sults two observations are in favor of a mechanism occur-
the reaction, a {[RPY2]CuIII2(µ-O2)}2ϩ species (Scheme 3). ring in the coordination sphere of the copper core: (1) hy-
In this context, it is reasonable to assume the formation of droxylation exclusively in the β position of the tertiary am-
species A and/or B upon reaction with dioxygen (Scheme ino group, and (2) exclusive cis hydroxylation of the amino-
3). Except with complexes derived from PhenPY2 and cyclopentane moieties of [cPtPY2]Cu(OTf)2. While we
IndPY2 ligands where activated benzylic hydrogen are pre- cannot definitively exclude a concerted mechanism, several
sent, such species do not transfer an oxygen atom to the examples in the literature are in favor of a two step mecha-
AlkylPY2 ligand. In a recent study on pMMO, Chan et al. nism where the abstraction of a β hydrogen atom occurs in
proposed that a CuIII2(µ-O2)2ϩ species is not reactive en- the partially rate determining step. Since AllPY2 is not the
ough to abstract a hydrogen atom from methane.[1d] Never- result of the dehydration of a copper(II) complex of [2a],[16]
theless, these authors suggested that transfer of an ad- the isolation of AllPY2 can be considered as being indica-
ditional electron, probably from another copper atom, and tive of a two-step mechanism where a carbenium ion is
the occurrence of the mixed valence CuIICuIII(µ-O2)2ϩ formed. The question which arises now is to know if this
species,[14] may enhance the reactivity of the copper-oxygen intermediate is formed directly by abstraction of a HϪ by
core. This hypothesis is very attractive for the hydroxylation an electrophilic oxygen (path c) or by oxidation of the rad-
of complexes derived from an AlkylPY2 ligand, which only ical E (path f). At the moment, it is difficult to answer this
occurs when benzoin is present. Thus, we propose that fundamental question. More experiments are needed, no-
benzoin acts in the monoelectronic reduction of A and/or tably using a radical clock fixed on the tertiary amino group
Eur. J. Inorg. Chem. 2000, 393Ϫ398
395

´
I. Blain, M. Giorgi, I. De Riggi, M. Reglier
FULL PAPER
Scheme 3. Oxydase vs. monooxygenase-like cycles
of the ligand. However, initial radical formation from a hy-
drogen atom abstraction by the CuϪO core seems to be
more reasonable since Mayer has recently shown that me-
tal-oxo complexes oxidize hydrocarbons by a hydrogen-
atom abstraction mechanism which is attributed to their
thermodynamic affinity for a hydrogen atom (ϵ Hϩ
ϩ
eϪ).[17]
Scheme 4. Mechanism proposed for β-hydroxylations
Conclusion
While benzylic hydroxylation is the easier process, we P2O5. Deoxygenation of solvents and solutions was carried out by
three vacuum/purge cycles. Standard Schlenk techniques were used
in the preparation and handling of air-sensitive compounds. Com-
mercial starting materials were used without further purification,
except for 2-vinylpyridine, which was distilled prior to use. NMR
spectra were recorded on Bruker AC-200 or AMX-400 spec-
trometers. Chemical shifts are reported in ppm as δ values down-
field from an internal standard (TMS). Elemental analyses were
obtained on a CHN Technicon microanalyser.
have now demonstrated that copper-oxygen species are able
to functionalise aliphatic CϪH bonds probably via a two-
step process. Once again, it is possible to show that the sub-
strate binding ligand approach gives valuable information
about the active species involved in the copper-dioxygen ac-
tivation. This organic chemistry approach is complemen-
tary to that of inorganic chemists who are more interested
in the structural study of copper-oxygen species
RPY2: To absolute MeOH were added freshly distilled 2-vinylpyri-
dine, the primary amine and acetic acid. After refluxing for 2Ϫ5
days, MeOH and the excess 2-vinylpyridine were evaporated under
vacuum. The crude product was dissolved in CH2Cl2, washed with
a saturated solution of NaHCO3 and dried over Na2SO4. Evapor-
Experimental Section
General: Solvents were freshly distilled under argon: MeOH from
Mg, Et2O from sodium benzophenone ketyl and CH2Cl2 from ation of CH2Cl2 under reduced pressure (18 Torr) and flash chro-
396 Eur. J. Inorg. Chem. 2000, 393Ϫ398

Substrate-Binding Ligand Approach in Chemical Modeling of Copper-Containing Monooxygenases, 1
FULL PAPER
matography (Silica gel, CH2Cl2/MeOH 85/15) afforded ligands
RPY2.
δ ϭ 11.6 (CH3), 20.0 (CH2), 35.6 (CH2), 54.1 (CH2), 56.2 (CH2),
61.5 (CH2), 70.8 (CH), 121.4 (CH), 120.5 (CH), 123.4 (CH), 122.2
(CH), 136.7 (CH), 136.6 (CH), 149.1 (CH), 148.6 (CH), 162.1 (C),
160.2 (C).
nPrPY2: Yield: 610 mg (2.3 mmol, 38%) [from n-propylamine
(354 mg,
6 mmol),
2-vinylpyridine
(3.88 mL,
36 mmol),
1b: 1H NMR (200 MHz, CDCl3): δ ϭ 1.20Ϫ1.80 (m, 8 H), 2.60
(dd, J ϭ 13 and 10 Hz, 1 H), 2.90Ϫ3.08 (m, 5 H), 3.14Ϫ3.32 (m,
1 H), 4.76 (dd, J ϭ 10 and 3 Hz, 1 H), 7.05Ϫ7.20 (m, 3 H),
7.50Ϫ7.72 (m, 3 H), 8.50 (m, 2 H). Ϫ 13C NMR (50.32 MHz,
CDCl3): δ ϭ 29.8 (CH2), 27.6 (CH2), 24.0 (CH2), 23.9 (CH2), 36.2
(CH2), 52.3 (CH2), 59.0 (CH2), 63.5 (CH), 71.0 (CH), 121.3 (CH),
120.4 (CH), 123.4 (CH), 122.2 (CH), 136.7 (CH), 136.5 (CH), 149.0
(CH), 148.6 (CH), 162.4 (C), 160.3 (C).
CH3COOH (420 mL, 7.5 mmol), MeOH (8 mL), 2 day reflux]. Ϫ
1H NMR (200 MHz, CDCl3): δ ϭ 0.83 (t, J ϭ 7.5 Hz, 3 H), 1.52
(hex, J ϭ 7.5 Hz, 2 H), 2.63Ϫ2.56 (m, 2 H), 3.00 (s, 8 H), 7.16Ϫ7.07
(m, 4 H), 7.57 (td, J ϭ 7.5 and 1.7 Hz, 2 H), 8.51 (ddd, J ϭ 4.8,
1.7 and 1 Hz, 2 H). Ϫ 13C NMR (50.32 MHz, CDCl3): δ ϭ 11.47
(CH3), 19.64 (CH2), 34.99 (CH2), 53.48 (CH2), 55.46 (CH2), 120.96
(CH), 123.18 (CH), 136.10 (CH), 148.82 (CH), and 159.86 (C).
cPtPY2: Yield: 1.18 g (4 mmol, 40%) [c-pentylamine (850 mg,
1
2a: H NMR (200 MHz, CDCl3): δ ϭ 1.08 (d, J ϭ 6.2 Hz, 3 H),
10 mmol), 2-vinylpyridine (10 mL, 0.1 mol), CH3COOH (2.3 mL,
1
2.35 (dd, J ϭ 12.9 and 9.9 Hz, 1 H), 2.48 (dd, J ϭ 12.9 and 3.1 Hz,
1 H), 2.70Ϫ3.10 (m, 8 H), 3.66 (dqd, J ϭ 9.9, 6.2 and 3.1 Hz, 1
H), 4.09 (br. s, 1 H), 6.97 (d, J ϭ 7.5 Hz, 2 H), 7.07 (ddd, J ϭ 7.5,
5.1 and 1.0 Hz, 2 H), 7.51 (td, J ϭ 7.5 and 1.7 Hz, 2 H), 8.48 (ddd,
J ϭ 5.1, 1.7 and 1.0 Hz, 2 H). Ϫ 13C NMR (50.32 MHz, CDCl3):
δ ϭ 19.5 (CH3), 35.6 (CH2), 53.9 (CH2), 62.1 (CH2), 63.5 (CH),
120.8 (CH), 123.9 (CH), 135.9 (CH), 148.7 (CH), 160.0 (C).
40 mmol), MeOH (10 mL), 5 day reflux]. Ϫ H NMR (200 MHz,
CDCl3): δ ϭ 1.32Ϫ1.74 (m, 6 H), 1.75Ϫ1.85 (m, 2 H), 2.90Ϫ3.10
(m, 9 H), 7.00Ϫ7.10 (m, 4 H), 7.52 (td, J ϭ 7.7 and 1.8 Hz, 2 H),
8.46 (dd, J ϭ 4.8 and 0.9 Hz, 2 H). Ϫ 13C NMR (50.32 MHz,
CDCl3): δ ϭ 23.93 (CH2), 30.10 (CH2), 35.71 (CH2), 51.80 (CH2),
63.71 (CH), 121.11 (CH), 123.38 (CH), 136.27 (CH), 149.13 (CH),
and 160.70 (C).
2b: 1H NMR (200 MHz, CDCl3): δ ϭ 1.53Ϫ1.62 (m, 1 H),
1.78Ϫ1.90 (m, 4 H), 1.95 (br. t, J ϭ 10 Hz, 1 H), 3.05Ϫ3.19 (m, 4
H), 3.23 (br. s, 1 H), 3.41Ϫ3.50 (m, 4 H), 4.35 (br. s, 1 H), 7.10
(ddd, J ϭ 8, 5 and 2 Hz, 2 H), 7.58 (td, J ϭ 8 and 2 Hz, 2 H), 7.16
(d, J ϭ 8 Hz, 2 H), 8.38 (br. d, J ϭ 5 Hz, 2 H). Ϫ 13C NMR
(50.32 MHz, CDCl3): δ ϭ 20.7 (CH2), 26.6 (CH2), 31.8 (CH2), 32.5
(CH2), 68.3 (CH), 51.0 (CH2), 70.4 (CH), 121.9 (CH), 123.7 (CH),
137.0 (CH), 149.0 (CH), 158.5 (C). Two-dimensional NMR experi-
ments were carried out on an AMX Bruker 400 MHz spectrometer.
COSY gradient, HMQC and HMBC experiments were performed
with 5 mm inverse broadband probehead incorporating a shielded
z-gradient coil. These correlations allowed the total assignment of
all the protons and carbon atoms of the compound 3b. A 5 mm
[RPY2]Cu(OTf)2: To a solution of Cu(OTf)2 (694 mg, 1.9 mmol) in
CH2Cl2 (5 mL) was added dropwise a solution of ligand RPY2
(1.9 mmol) in CH2Cl2 (5 mL). The mixture was allowed to stir for
2 h, and Et2O was added until precipitation. The precipitate ob-
tained was centrifuged, washed with Et2O and dried in vacuo to
give [RPY2]Cu(OTf)2.
[nPrPY2]Cu(OTf)2: blue solid. Ϫ Yield: 1.10 g (1.66 mmol, 87%)
Ϫ C19H23CuF6N3O6S2 (631.06): calcd. C 36.16, H 3.67, N 6.66;
found C 35.16, H 3.88, N 6.47.
[cPtPY2]Cu(OTf)2: blue solid. Ϫ Yield 1.23 g (1.78 mmol, 94%) Ϫ
C21H25CuF6N3O6S2 (657.10): calcd. C 38.39, H 3.83, N 6.39; found
C 37.36, H 4.03, N 6.22.
1
DUAL H/13C probehead was used to acquire the 2D phase-sensi-
Oxidation of [RPY2]CuPF6 With O2: To
a solution of
tive NOESY data.
[CH3CN]4CuPF6 (0.1 mmol) in degassed CH2Cl2 (50 mL), was ad-
ded dropwise a solution of RPY2 (0.1 mmol) in CH2Cl2 (50 mL).
The mixture was stirred under argon for 1 h, and then exposed to
an O2 atmosphere for 24 h. The CH2Cl2 was subsequently evapo-
rated in vacuo, Et2O (50 mL) was added, and the precipitate thus
obtained was filtered off, washed with Et2O, and dried in vacuo to
give a mixture of copper(II) complexes. This mixture was dissolved
in CH2Cl2 (20 mL), washed with 35% NH4OH (5 mL) and brine
(3 ϫ 5 mL), and dried over Na2SO4. Evaporation of the CH2Cl2
under reduced pressure (18 Torr) gave the crude product. Flash
chromatography (SiO2, CH2Cl2/MeOH, 90:10) afforded the reco-
vered ligands RPY2.
1
AllPY2: H NMR (200 MHz, CDCl3): δ ϭ 2.90 (br. s, 8 H), 3.25
(d, J ϭ 6 Hz, 2 H), 5.10 (br. d, J ϭ 10 Hz, 1 H), 5.18 (br. d, J ϭ
17 Hz, 1 H), 5.80 (ddt, J ϭ 17, 10 and 6 Hz, 1 H), 7.10Ϫ6.90 (m,
4 H), 7.50 (td, J ϭ 8 and 2 Hz, 2 H), 8.50 (dt, J ϭ 5 and 1 Hz, 2
H). Ϫ 13C NMR (50.32 MHz, CDCl3): δ ϭ 35.7 (CH2), 53.3 (CH2),
58.8 (CH2), 116.9 (CH2), 120.7 (CH), 123.0 (CH), 135.5 (CH),
135.8 (CH), 146.8 (CH), 160.3 (C).
X-ray Structure Analysis: Crystal data for [nPrPY2]Cu(OTf)2 to-
gether with details of the X-ray diffraction experiment, are reported
in Table 1. Crystallographic data for the structure reported in this
paper has been deposited at the Cambridge Crystallographic Data
Center as supplementary publication no. CCDC 113535. Copies of
the data can be obtained free of charge on application to The Di-
rector, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax:
(internat.) ϩ 44-1223/336-033, E-mail: deposit@ccdc.cam.ac. uk].
Oxidation of [RPY2]Cu(OTf)2 With O2 in the Presence of Benzoin:
To a solution of [RPY2]Cu(OTf)2 in degassed CH2Cl2 were added
benzoin (1 equiv.) and NEt3 (1 equiv.). This mixture was stirred
under argon for 2 h and then exposed to an O2 atmosphere for
24 h. The CH2Cl2 was subsequently evaporated in vacuo and Et2O
was added. The precipitate thus obtained was filtered off, washed
with Et2O, dissolved in CH2Cl2, washed with 35% NH4OH and
brine, and dried over Na2SO4. Evaporation of the CH2Cl2 under
reduced pressure (18 Torr) gave a mixture of recovered ligands
RPY2 and compounds 1a,b, 2a,b and AllPY2 which were separated
by flash chromatography (SiO2, CH2Cl2/MeOH, 90:10).
Acknowledgments
This research was supported by the CNRS and the French Ministry
of Universities. The authors are grateful to Dr. A. Heumann for a
number of enlightening discussions.
1
1a: H NMR (200 MHz, CDCl3): δ ϭ 0.75 (t, J ϭ 7 Hz, 3 H), 1.4
[1]
[1a] General references on copper-containing enzymes: J. P. Klin-
(m, 2 H), 2.4Ϫ2.7 (m, 3 H), 3.1Ϫ2.85 (m, 5 H), 4.75 (dd, J ϭ 9
and 3.4 Hz, 1 H), 6.95 (d, J ϭ 7.5 Hz, 1 H), 7.2Ϫ7.05 (m, 4 H,),
7.4Ϫ7.7 (m, 3 H), 8.50 (m, 2 H). Ϫ 13C NMR (50.32 MHz, CDCl3):
man, Chem. Rev. 1996, 96, 2541Ϫ2561; W. Kaim. J. Rall, An-
gew. Chem. 1996, 108, 47Ϫ64; Angew. Chem. Int. Ed. Engl.
[1b]
1996, 35, 43Ϫ60. Ϫ
Dopamine β-hydroxylase (DBH),
Eur. J. Inorg. Chem. 2000, 393Ϫ398
397

´
I. Blain, M. Giorgi, I. De Riggi, M. Reglier
FULL PAPER
benzylic hydroxylation of dopamine into noradrenaline: L. C.
inson, G. Pan, X. Wang, V. G. Young Jr., C. J. Cramer, L. Que
Jr., W. B. Tolman, J. Am. Chem. Soc. 1996, 118, 11555Ϫ11574;
S. Mahapatra, J. A. Halfen, W. B. Tolman, J. Am. Chem. Soc.
1996, 118, 11575Ϫ11586; C. J. Cramer, B. A. Smith, W. B. Tol-
man, J. Am. Chem. Soc. 1996, 118, 11283Ϫ11287; J. Cahoy, P.
L. Holland, W. B. Tolman, Inorg. Chem. 1999, 38, 2161Ϫ2168.
K. D. Karlin, J. C. Hayes, Y. Gultneh, R. W. Cruse, J. W.
McKown, J. P. Hutchinson, J. Zubieta, J. Am. Chem. Soc. 1984,
106, 2121Ϫ2128.
Stewart, J. P. Klinman, Ann. Rev. Biochem. 1988, 57, 551Ϫ592.
[1c]
Ϫ
Peptidylglycine α-hydroxylating monooxygenase (PHM),
neuropeptide amidation: S. T. Pridge, A. S. Kolhenar, B. A.
Eipper, R. E. Mains, L. M. Amzel, Science 1997, 278,
[1d]
1300Ϫ1305.
Ϫ
Particulate methane monooxygenase
[9]
(pMMO), methane hydroxylation into methanol: S. J. Eliot, M.
Zhu, L. Tso, H.-H. T. Nguyen, J. H.-K. Yip, S. I. Chan, J. Am.
Chem. Soc. 1997, 119, 9949Ϫ9955.
[10] [10a]
[2] [2a]
´
´
E. Amadei, E. H. Alilou, F. Eydoux, M. Pierrot, M. Reglier,
K. D. Karlin, S. Kaderli, A. D. Zuberbühler, Acc. Chem.
[2b]
B. Waegell, J. Chem. Soc., Chem. Commun. 1992, 1782Ϫ1784.
Res. 1997, 30, 139Ϫ147. Ϫ
W. B. Tolman, Acc. Chem. Res.
[10b]
[2c]
´ ´
M. Reglier, E. Amadei, E. H. Alilou, F. Eydoux, M.
Ϫ
1997, 30, 227Ϫ237. Ϫ
N. Kitajima, Y. Moro-Oka, Chem.
Pierrot, B. Waegell, Bioinorganic Chemistry of Copper (Eds.: K.
Rev. 1994, 94, 737Ϫ757.
[3]
D. Karlin, Z. Tiecklar), Chapman and Hall, 1993, pp. 348Ϫ362.
N. Kitajima, K. Fujisawa, Y. Moro-Oka, K. Toriumi, J. Am.
[10c]
Ϫ
´
I. Blain, P. Bruno, M. Giorgi, E. Lojou, D. Lexa, M.
Chem. Soc. 1989, 111, 8975Ϫ8976.
Reglier, Eur. J. Inorg. Chem. 1998, 1297Ϫ1304.
N-Dealkylation is a process already observed in the reaction of
[BnPY2]CuPF6 with dioxygen: I. Sanyal, M. Mahroof-Tahir,
M. S. Nasir, P. Ghosh, Y. Gultneh, R. W. Cruse, A. Farooq, K.
D. Karlin, S. Liu, J. Zubieta, Inorg. Chem. 1992, 31, 4322Ϫ4332.
An authentic sample of compound 2a was obtained by addition
of 2-hydroxypropylamine to vinylpyridine in a methanol/acetic
acid mixture.
[4] [4a]
H. V. Obias, Y. Lin, N. N. Murthy, E. Pidcock, E. I. Solo-
[11]
mon, M. Ralle, N. J. Blackburn, Y.-M. Neuhold, A. D. Zub-
erbühler, K. D. Karlin, J. Am. Chem. Soc. 1998, 120,
[4b]
12960Ϫ12961. Ϫ
M. A. Lockwood, T. J. Blubaugh. M.
Coler, S. Lovell, J. M. Mayer, Angew. Chem. Int. Ed. 1999, 38,
[12]
[13]
225Ϫ227.
[5]
[6]
S. Itho, T. Kondo, M. Komatsu, Y. Ohshiro, C. Li, N. Kanehisa,
Y. Kai, S. Fukuzumi, J. Am. Chem. Soc. 1995, 117, 4714Ϫ4715;
S. Itho, H. Nakao, L. M. Berreau, T. Kondo, M. Komatsu, S.
Fukuzumi, J. Am. Chem. Soc. 1998, 120, 2890Ϫ2899.
A sample of trans-2b was obtained by addition of PY2 to cyclo-
pentene oxide and compared to the product obtained by β-hy-
droxylation.
[14]
[15]
T. N. Sorrel, W. E. Allen, P. S. White, Inorg. Chem. 1995, 34,
952Ϫ960; W. E. Allen, T. N. Sorrell, Inorg. Chem. 1997, 36,
1732Ϫ1734.
A. P. Cole, D. E. Root, P. Mukherjee, E. I. Solomon, T. D. P.
Stack, Science 1996, 273, 1848Ϫ1850.
Another possibility is to consider the occurrence of a mononu-
clear CuIIϪO• ( CuIIIϪOϪ) species D that could result from
a dissociation of C.
[7] [7a]
S. Mahapatra, J. A. Halfen, E. C. Wilkinson, L. Que, Jr.,
[7b]
W. B. Tolman, J. Am. Chem. Soc. 1994, 116, 9785Ϫ9786. Ϫ
[16]
S. Mahapatra, J. A. Halfen, E. C. Wilkinson, G. Pan, C. J.
The copper(II) complex of 2a placed under O2/Benzoin/NEt3
does not produce any AllPY2 compound.
Cramer, L. Que Jr., W. B. Tolman, J. Am. Chem. Soc. 1995, 117,
[7c]
[17] [17a]
8865Ϫ8866. Ϫ
J. A. Halfen, V. G. Young Jr., W. B. Tolman,
K. Wang, J. M. Mayer, J. Am. Chem. Soc. 1997, 119,
[17b]
J. Am. Chem. Soc. 1996, 118, 10920Ϫ10921.
1470Ϫ1471. Ϫ
441Ϫ450.
J. M. Mayer, Acc. Chem. Res. 1998, 31,
[8]
J. A. Halfen, S. Mahapatra, E. C. Wilkinson, S. Kaderli, V. C.
Young Jr., L. Que Jr., A. D. Zuberbühler, W. B. Tolman, Science
1996, 271, 1397Ϫ1400; S. Mahapatra, J. A. Halfen, E. C. Wilk-
Received June 4, 1999
[I99203]
398
Eur. J. Inorg. Chem. 2000, 393Ϫ398