Electronic effects in olefin oxidation by imidoosmium(VIII) compounds

Article abstract of DOI:10.1002/ejoc.200300774

Imido osmium(VIII) complexes are versatile oxidants for C-C double bond functionalisation. Despite their structural similarity with OsO₄ their reactivity cannot always be compared with this seminal reagent. Detailed investigations including kinetic competition experiments are presented that uncover the electronic and steric preferences of osmium imido complexes. The different behaviour of OsO₄ and its imido derivatives towards tertiary amines and diamines is clarified. Hammett correlation studies reveal that the reactivity spectrum of the respective oxidants ranges from a strongly electrophilic behaviour in the case of OsO₄ to a rather nucleophilic character as encountered for OsO(NtBu)₃. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejoc.200300774

FULL PAPER
Electronic Effects in Olefin Oxidation by Imidoosmium(VIII) Compounds
[a]
˜
Kilian Muniz
Dedicated to Prof. Dr. Edgar Niecke on the occasion of his 65th birthday
Keywords: Osmium / Oxidations / Imido compounds / Diamination / Heterocycles
Imido osmium(VIII) complexes are versatile oxidants for C−C
double bond functionalisation. Despite their structural simil-
derivatives towards tertiary amines and diamines is clarified.
Hammett correlation studies reveal that the reactivity
arity with OsO4 their reactivity cannot always be compared spectrum of the respective oxidants ranges from a strongly
with this seminal reagent. Detailed investigations including
kinetic competition experiments are presented that uncover
the electronic and steric preferences of osmium imido
complexes. The different behaviour of OsO4 and its imido
electrophilic behaviour in the case of OsO4 to a rather nucle-
ophilic character as encountered for OsO(NtBu)3.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
Introduction
fin substrate classes is believed to be well understood.[1,10]
In the 1970s, Sharpless reported the general reactivity pat-
tern for isolated imido osmium() complexes and pre-
sented selected examples of oxidative conversion of olefin
classes employing these reagents.[11Ϫ13] We have recently
been interested in the chemistry of the related bis- and tris-
(imido)osmium complexes 3 and 4.[14Ϫ16] During the course
of this investigation, several results were encountered that
could not be explained by simply employing the parent os-
mium tetroxide as a model oxidant. At the same time, there
remain certain open features such as chemo- and regioselec-
tivity in aminohydroxylation protocols[5,6,9] that require a
deeper understanding of the imido osmium complexes in-
volved. Certainly, a precise knowledge of the electronic
properties of complexes such as 2Ϫ4 is needed and will be
indispensable for the development of new reactivity in this
area.
Selective oxidative 1,2-functionalisation by means of de-
fined osmium complexes is the basis of the epoch-making
catalytic asymmetric Sharpless dihydroxylation[1Ϫ4] and
aminohydroxylation[5,6] reactions.[7] These reactions employ
the tertiary quinuclidine amino group of Cinchona alkaloids
for chiral modification of the osmium reagent[1] and for en-
hancement of the overall reaction rate.[8] The active oxidat-
ive species in these reactions is either osmium tetroxide
OsO4 (1) or a monoimido trioxoosmium compound which
is generally obtained from in situ formation of an os-
mium() compound and a suitable nitrene precursor. These
reagents have not yet been characterised and preformed im-
ido complexes with a tertiary alkyl substituent at nitrogen
such as 2 remain the only stable derivatives known to
date.[9] Moreover, no detailed comparative studies on the
reactivities of osmium oxidants 1Ϫ4 (Figure 1) have been
undertaken. Owing to the vast interest in dihydroxylations,
osmium tetroxide and its chemistry have received much at-
tention and its oxidative behaviour toward all kinds of ole-
We have thus embarked on a detailed study of the elec-
tronic effects involved in olefin oxidation with complexes
2Ϫ4 and here offer a concise discussion of the differences
in electronic features between the common imido osmium
complexes 1Ϫ4 and their consequences for oxidative olefin
functionalisation.
Results and Discussion
Electronic Effects of the Substrates
Figure 1. Osmium oxidants 1Ϫ4
The general preference of 3 and 4 for electron-deficient
olefins as substrates was known from previous
investigations.[13Ϫ16] In addition, a competition experiment
for oxidation of dimethyl fumarate had revealed a higher
reaction rate for these reagents than for the related com-
pounds 1 and 2.[15] In fact, the relative reactivities in the
[a]
´
Kekule-Institut für Organische Chemie und Biochemie,
Rheinische Friedrich-Wilhelms-Universität,
Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
Fax: (internat.) ϩ 49-(0)228-735813
E-mail: kilian.muniz@uni-bonn.de
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Eur. J. Org. Chem. 2004, 2243Ϫ2252
DOI: 10.1002/ejoc.200300774
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K. Mun˜iz
FULL PAPER
oxidation of dimethylfumarate were found to follow the or-
der: k(4) Ͼ k(3) ϾϾ k(2) ϭ k(1). It is particularly signifi-
cant that the sterically very congested tris(imido) species 4
reacts faster than the bis(imido) reagent 3. This indicates
that electronic, not steric, properties are important in the
oxidation of electron-deficient olefins with imido complexes
(Scheme 1). As a second important observation, compound
2 leads to diol and amino alcohol formation while 3 and 4
display complete chemoselectivity and undergo exclusively
diamination reactions.
Table 1. Styrene oxidation by osmium oxidants 1Ϫ4
Entry Oxidant Time Product(s) Yield Chemoselectivity
[h]
[%][a]
1
1
2
3
4
12
20
20
20
11
85
59
76
94
Ϫ
2[b]
3[c]
4[d]
11, 12
12, 13
12, 13
Ͼ 95:5 (12:11)
91:9 (13:12)
Ͼ 98[e] (13:12)
[a] Combined yield of products after reductive workup. [b] Literature
value: 63% yield, 99:1 chemoselectivity (ref.[11]). [c] Literature value:
83% yield, 88:12 chemoselectivity (in CCl4, ref.[11,12]). Literature
[d]
value: 92% yield, 97:3 chemoselectivity (in CCl4, ref.[11,12]). De-
[e]
tection of a single set of signals in the respective 300-MHz 1H
NMR spectrum.
electron-withdrawing substrates such as dimethyl fumarate,
which showed complete chemoselectivity with 3 but rather
low chemoselectivity with 2, is altered for reaction with neu-
tral olefins (Scheme 2, Table 1). Oxidation with 2 leads al-
most exclusively to amino alcohol formation while 3 gives
an approximately 10:1 ratio for diamine/amino alcohol. A
second set of experiments with (E)-stilbene as substrate was
rather difficult to interpret. Dihydroxylation with 1 gave the
usual high yield that is known for this particular substrate
from both stoichiometric and catalytic reactions.[1,2] In con-
trast, oxidation with 2 yielded a nearly equimolar mixture
of diol and amino alcohol and both reagents 3 and 4 gave
amino alcohol formation only (Scheme 3, Table 2).
Scheme 1. Oxidation of dimethyl fumarate[15]
However, the stated reactivity order was found to be re-
versed when oxidation of styrene was investigated. In this
case, osmium tetroxide 1 gave a high yield of 89% after 12 h
at room temperature while the imido compounds reacted
more slowly (Scheme 2, Table 1). This is exemplified best
by comparison of the respective product formation from
oxidations of styrene with 1 and 4 (Scheme 2, below).
Scheme 3. Oxidation of (E)-stilbene
Table 2. Stilbene oxidation by osmium oxidants 1Ϫ4
Entry Oxidant Temp. (°C) Time Product Yield Chemoselectivity
[h]
[%]
[a]
1
2
3
4
1
2
3
4
room temp. 12
room temp. 20
15
89
Ϫ
15, 16 56[b] Ͼ 55:45 (15:16)
70
70
36
36
16
16
41[c] Ͼ 98[d] (16)
23[e] Ͼ 98[d] (16)
[a]
Together with ca. 12% benzaldehyde (6% yield); 100% overall
conversion. [b] Combined yield of products; 41% recovered starting
[c]
material.
Together with ca. 18% benzaldehyde (9% yield); 55%
conversion. [d] Detection of a single 1,2-difunctionalization product
in the respective 300-MHz 1H NMR spectrum.
Together with
[e]
ca. 28% benzaldehyde (14% yield); 40% conversion.
The apparent differences in comparison to the respective
oxidations of styrene are not due to electronic reasons but
arise from the additional steric hindrance between the olefin
and the bulky tert-butyl-substituted imido reagents. It
Scheme 2. Oxidation of styrene with oxidants 1Ϫ4 and comparison
between 1 and 4 in styrene oxidation
These observations suggest a relative change of reactivity should be noted that the absence of diamine formation in
in going from 5 to 10. Apparently, the observed trend from the reactions with 3 and 4 is without precedent.
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Electronic Effects in Olefin Oxidation by Imidoosmium(VIII) Compounds
FULL PAPER
An investigation of the relative reactivities of 3 towards
This result again underlines the importance of electron-
electron-deficient olefins showed nearly equal reactivity for demanding substituents in ensuring high reactivity in olefin
diamination of methyl cinnamate and dimethyl fumarate diamination. These general trends in reactivity of 3 and 4
(Scheme 4).[15] Apparently, there is negligible electronic in- toward electronically different CϭC bonds is best illus-
fluence from the second electron-withdrawing group. Im- trated by the reaction of 3 with vinyl acrylate which rep-
portantly, this similarity in reactivity is no longer observed resents a substrate with two electronically different CϭC
for competition experiments involving monosubstituted ole- bonds (Scheme 6).
fins such as styrene and methyl acrylate. Here, the electron-
demanding olefin undergoes a faster reaction (Scheme 5).
Scheme 6. Chemoselective CϪC-double bond diamination
In this competition experiment, complete chemoselectiv-
ity regarding the reagent (exclusive diamination, no dihy-
droxylation or aminohydroxylation) and the substrate (ex-
clusive oxidation of the acrylate CϪC double bond over the
vinylic one) takes place and 22 is formed selectively as the
only product out of eight possible ones!
In general, electron-demanding CϭC bonds undergo fas-
ter diamination than neutral or electron-rich ones. With re-
gards to acceptor-substitution, one electron-withdrawing
group is apparently sufficient for the reaction to reach
maximum rate. These conclusions hold true for all sub-
strates investigated so far. A single exception has been ob-
served for ferrocenyl acrylates, which will be discussed else-
where.[17]
Ligand Coordination
Scheme 4. Competition experiment for diamination with 3: elec-
tron-demanding olefins
Coordination of mono-amine ligands such as DABCO or
quinuclidine to OsO4 or its monoimido derivatives usually
increases the reactivity and enhances the chemoselectivity
in case of aminohydroxylation with 2 and related alkylim-
ido complexes.[8] The same holds true for the naturally oc-
curring Cinchona alkaloids dihydroquinine and dihydro-
quinidine which create a chiral environment around os-
mium and thereby guarantee that an asymmetric induction
takes place. This principle of reversible ligand coordination
and beneficial rate enhancement for the desired chiral oxi-
dant was established as Ligand Accelerated Catalysis (or Li-
gand Accelerated Synthesis in the case of stoichiometric re-
action conditions).[8]
In indicative sets of experiments no difference in rate was
observed for diamination of dimethyl fumarate or methyl
cinnamate in the absence or presence of potential ligands
such as quinuclidines, DABCO or pyridine. As a result, it
was impossible to induce asymmetry in the diamination re-
actions of various olefins with reagents 3 and 4.
1
Careful H NMR studies for different ratios of 3 and the
standard first-generation PCB ligand of DHQD (23)[1] did
not suggest any complexation at all.[18] Selected NMR spec-
tra for such investigations are reproduced in Figure 2. This
observation is in notable contrast to a related titration study
of monoimido complex 2 with 23, which indicated coordi-
nation between the respective quinuclidine unit and 2.[19]
Scheme 5. Competition experiment for diamination with 3:
electron-demanding vs. neutral olefin
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K. Mun˜iz
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1
Figure 2. H NMR spectra for titration of 3 with Cinchona alkaloid 23 [for ratios of 23/3, 1:1 (a), 5:1 (b) and 20:1 (c)]
Moreover, several reports of spectral investigation of Cin-
chona alkaloid complexes of 1 have become available.[20] For
3 and 4, the apparent inability to complex external nitrogen
ligands stems from the presence of two basic imido groups
which saturate the Os centre through alternating electron
donation from the nitrogen lone pairs. Such electronic satu-
ration removes all electrophilicity at the OsVIII centre and
thereby prevents it from coordinating with external nitro-
gen donors.
Conceptually different approaches in the area of stoichio-
metric asymmetric dihydroxylation reactions have employed
vicinal diamines. These compounds form stable chelate ad-
ducts with osmium tetroxide to furnish extremely reactive
dihydroxylating reagents. For example, Corey has reported
a chelate complex from 1 and N,NЈ-bis(mesitylidene) di-
phenylethylenediamine that displays high reactivity even at
a temperature as low as Ϫ70 °C.[21] Moreover, the diamine
Scheme 7
adducts of the resulting osmate esters are known to have
enhanced resistance to hydrolysis.[22] Finally, Donohoe re-
cently succeeded both in the use of TMEDA/1 combi-
nations for directed dihydroxylation reactions[23,24] and in
the isolation of an azaglycolate product from intramolecu-
lar aminohydroxylation by TMEDA complexation.[25]
A competition experiment between OsO4/TMEDA and
It was anticipated that complexation of 2 with TMEDA OsO3NtBu/TMEDA yielded, after reductive workup, di-
would greatly enhance the reactivity and thereby the methyl tartrate 6 as the only product. This is a surprising
amount of aminohydroxylation over dihydroxylation. In- reaction outcome taking into account the preferred reactiv-
deed, reaction of 2 with dimethyl fumarate (5) in the pres- ity of free 2 over free 1 as established previously.[15] Careful
ence of TMEDA gave the expected complex 25 (Scheme 7). NMR studies revealed that there is no apparent interaction
Since the primarily formed N-(tert-butyl)azaglycolate has between the monoimido reagent 2 and TMEDA. Over the
been shown to be rather unstable,[11,12] isolation of 25 pro- whole temperature range of Ϫ80 to ϩ20 °C only the signals
ves the beneficial influence of the chelating diamine in sta- of the respective free, uncomplexed compounds appeared.
bilising the azaglyolate osmium intermediate as already ob- This indicates an explanation for the reaction outcome from
served by Donohoe. Product 25 was isolated as an insepar- Scheme 7. Apparently, formation of the observed TMEDA
able mixture of two isomers. In accordance with the NMR chelate 25 takes place during the process of warming to
spectroscopic data, the existence of these two diastereoiso- room temperature, and complexation of TMEDA to Os oc-
mers is assumed to be due to a λ/δ-conformation of the curs only after initial formation of the azaglycol osmate(VI)
TMEDA ligand in 25 (Scheme 7).
ester has already taken place.
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Electronic Effects in Olefin Oxidation by Imidoosmium(VIII) Compounds
FULL PAPER
Since OsO4 does readily interact with TMEDA even at
low temperatures in the region of Ϫ80 °C, the OsO4/
TMEDA combination produces the kinetically preferred
oxidant leading to formation of 6 only (Scheme 7, below).
Hammett Correlations
We further quantified the observations on electronic in-
fluence and have investigated the respective Hammett corre-
lations for diaminations with imido reagents 3 and 4. 4-
Phenyl-substituted cinnamates were chosen as substrates for
this investigation.
For osmium tetroxide (1) a nonlinear plot was observed.
Such a behaviour was also observed by Sharpless for related
Os-catalysed reactions in the presence of a chiral tertiary
amine ligand.[26] If the data for the p-NO2/p-H pair is omit-
ted, a linear regression gives a p-value of Ϫ0.55 (Figure 3)
which is in good agreement with the expected electrophilic
character of the 16e-oxidant 1. A comparable result had
been determined by Henbest for dihydroxylation of styr-
enes.[27]
Initial attempts to undertake the same investigation with
Figure 4. Hammet plot for diamination of 4-substituted cinnamates
by bis(imido) reagent 3
the monoimido complex 2 were hampered by the low
chemoselectivity of this reagent and the problematic identi-
fication of some of the reaction products. However, it had
already been noted by Sharpless that 2 represents a slightly
softer oxidant than 1 and thus should be regarded as an
electrophilic reagent with less pronounced character than
1.[11,12] This can be explained by the electron lone pair at
the imido nitrogen atom which upon coordination to the
metal centre diminishes the electrophilicity. Such an as-
sumption is strengthened by X-ray analyses which show a
linear imido ligand with a formal 4e count.[28]
Complex 3 displays a different reactivity pattern, and
nearly no electronic influence was observed in the respective
oxidations of cinnamates (Figure 4). This observation
matches the previous finding that a single electron-with-
drawing group is sufficient to reach the optimum rate
(Scheme 4). The final Hammett correlation gives a ρ-value
of ϩ0.05 which renders 3 a neutral or slightly nucleophilic
oxidant.
Reaction of 4 with unsymmetrically substituted olefins
forms osmaimidazolidines with a stereogenic metal centre.
Thus, a mixture of two diastereomers is obtained.[29] Ap-
Figure 3. Hammet plot for dihydroxylation of 4-substituted cinna-
mates by OsO4
Scheme 8. Diamination of 4-substituted cinnamates with tris(imido) reagent 4
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K. Mun˜iz
FULL PAPER
parently, the diastereomeric ratios are nearly independent Conclusion
of the 4Ј-substitution (Scheme 8, Table 3). As in the case of
We have described a detailed investigation of the elec-
tronic nature of imido Os complexes and the resulting
consequences for CϪC double bond functionalisation. As
a result of the obtained data, it is evident that osmium tet-
roxide 1 cannot be directly compared with its imido com-
plexes 2, 3 and 4 in respect of reactivity in olefin oxidation.
While 1 must be characterised as an electrophilic reagent,
this property is diminished by the introduction of sub-
sequent imido groups which results in a dramatically altered
reactivity. Thus, bis(imido) complex 3 is a nearly electroneu-
tral oxidant, while the tris(imido) derivative 4 is a nucleo-
philic oxidant in the oxidation of electron-demanding olef-
ins. Ongoing work is therefore centred on the investigation
of the mechanistic pathways involved in olefin oxidation
with bis- and tris(imido) osmium() complexes.
the related diamination reactions employing reagent 3, all
new compounds were first synthesised in independent reac-
tions and fully characterised. The diastereomeric ratios of
each diamination reaction could thus be assured indepen-
dently.
Table 3. Diamination of 4-substituted cinnamates with tris(imido)
reagent 4
[a]
Entry Substrate (X) Products Yield
Diastereomeric ratio[b]
1
2
3
4
5
OCH3
Br
H
CH3
NO2
35, 36
37, 38
39, 40
41, 42
43, 44
82
88
93
89
96
59:41
61:39
58:42
63:37
68:32
[a]
[b]
Combined yield after purification by column chromatography.
Determined from the crude H NMR spectrum.
Experimental Section
1
General Remarks: Osmium() oxide was purchased from Strem.
tert-Butylamine, N-(trimethylsilyl)-tert-butylamine, methyl cinna-
mate, methyl acrylate and (DHQD)2PHAL were purchased from
Fluka. Dimethyl fumarate, stilbene, styrene and vinyl acrylate were
purchased from Aldrich. The following reaction products represent
known compounds described previously: 7Ϫ9, 11Ϫ13, 15, 18, 20,
26Ϫ30.[11Ϫ13,15,30Ϫ33]
For the competition experiments of the Hammett corre-
lation, product ratios and thus the values for the relative
reaction rates were calculated back to the sum of both dia-
stereomers in question and the final Hammett correlation
gave a ρ-value of ϩ0.28 (Figure 5). This result characterises
4 as a pronounced nucleophilic oxidant.
THF, n-hexane and toluene were distilled from sodium/benzo-
phenone ketyl radical under argon and saturated with argon. Di-
chloromethane and triethylamine were distilled from CaH2 under
argon. All other solvents were reagent grade and used as received.
Column chromatography was performed with silica gel (Merck,
type 60, 0.063Ϫ0.2 mm and MachereyϪNagel, type 60,
0.015Ϫ0.025 mm). Optical rotations were measured with
a
PerkinϪElmer 341 polarimeter. Concentrations are given in g/
100 mL as dichloromethane solutions. NMR spectra were recorded
with Bruker DPX 300 MHz and Bruker DRX 500 MHz spec-
trometers. All chemical shifts in NMR experiments are reported as
ppm downfield from TMS. The following calibrations were used:
CDCl3: δ ϭ 7.26 and 77.00 ppm, C6D6: δ ϭ 7.16 and 128.00 ppm.
IR spectra were recorded with a Nicolet Magna 550 FT-IR spec-
trometer. MS and HRMS experiments, and elemental analyses were
performed with a Kratos MS 50 and an Elementar Analysensystem
Figure 5. Hammett correlation for diamination of cinnamates
with 4
´
Vario EL, respectively, within the service centres at the Kekule De-
partment, Bonn.
2-tert-Butylamino-1,2-diphenylethanol (16): This was obtained from
the reaction between (E)-stilbene (360 mg, 2.0 mmol) and complex
3 (382 mg, 1 mmol) in freshly distilled THF (10 mL). After stirring
As a consequence of all these studies, osmium tetroxide
(1) and the imido derivatives 2Ϫ4 cannot be compared di-
rectly regarding their performance in CϭC bond oxidation. at 70 °C for 36 h, the dark reaction mixture was treated with an
aqueous thiosulfate solution and submitted to acid/base extraction
with dichloromethane as organic solvent. The organic layers were
dried with MgSO4 and the solvents evaporated under reduced
pressure to leave the title compound (111 mg, 0.41 mmol, 41%) as
While performance of 1 is known to be most efficient in the
oxidation of terminal and (Z)-configured neutral or elec-
tron-rich olefins,[1] imido compounds such as 2 with their
reduced electrophilicity give best results with terminal or
(E)-substituted neutral olefins.[9] In contrast, the bis(imido)
complex 3 has a strong preference for (E)-configured elec-
tron-poor olefins, while tris(imido) complex 4 with its
strong steric hindrance reacts only with terminal or (E)-
substituted olefins[9,13] and is characterised by its nucleo-
philicity.
1
a colourless to light-yellow oil which solidified upon standing. H
NMR (300 MHz, CDCl3): δ ϭ 1.15 (s, 9 H), 3.73 (d, J ϭ 9.5 Hz,
1 H), 4.58 (d, J ϭ 9.5 Hz, 1 H), 7.04Ϫ7.46 (m, 10 H) ppm. 13C
NMR (75 MHz, C6D6): δ ϭ 30.62, 65.77, 68.37, 87.22, 126.52,
126.89, 127.61, 128.51, 128.67, 134.85, 146.56 ppm. IR (KBr): ν˜ ϭ
3011, 2967, 2833, 2111, 1365, 1103, 1074, 993, 894 cmϪ1. MS (EI,
eV): m/z (%) ϭ 270 (55) [M]ϩ, 213 (22), 199 (86), 138 (28), 77 (100).
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Electronic Effects in Olefin Oxidation by Imidoosmium(VIII) Compounds
FULL PAPER
C19H23NO: calcd. C 80.26, H 8.61, N 5.20; found C 80.53, H 8.56,
N 5.43.
ppm. MS (EI, eV): m/z (%) ϭ 572 (8) [M]ϩ, 557 (8), 499 (89), 443
(100), 387 (269, 359 (10), 134 (16). HRMS: calcd. for
C20H32N2O5188Os: 568.2270; found 568.2268.
General Procedure for Diamination of Achiral Olefins with Osmium
Imido Complexes 3 and 4: The solid bis(imido) osmium complex 2
was added to a solution of the appropriate olefin (1.2 mmol) in
freshly distilled THF in one portion and the resulting solution was
stirred at room temperature overnight (approx. 12 h). The solvent
was evaporated under reduced pressure and the remaining crude
oily residue analysed by NMR spectroscopy. The pure product was
obtained by column chromatography as indicated for the individ-
ual compound.
Ethyl trans-5-(4Ј-Bromophenyl)-1,3-bis(tert-butyl)-2,2-dioxo-2-os-
ma(VI)imidazolidine-4-carboxylate (32): This was obtained from the
reaction between ethyl 4Ј-bromocinnamate (153 mg, 0.6 mmol) and
the bis(imido) compound 3 (181 mg, 0.5 mmol) according to the
general procedure. Purification by column chromatography (ethyl
acetate/hexanes, 1:3, v/v) gave the title compound as a purple solid
(262 mg, 0.44 mmol, 87%). M.p. 122 °C (dec.). 1H NMR
(300 MHz, C6D6): δ ϭ 1.03 (t, J ϭ 7.2 Hz, 3 H), 1.05 (s, 9 H), 1.12
(s, 9 H), 3.94 (q, J ϭ 7.2 Hz, 2 H), 4.21 (s, 1 H), 4.85 (s, 1 H), 7.01
(d, J ϭ 9.2 Hz, 2 H), 7.17 (d, J ϭ 9.2 Hz, 2 H) ppm. 13C NMR
(75 MHz, C6D6): δ ϭ 12.72, 28.45, 29.27, 60.13, 65.38, 66.15, 80.24,
83.75, 120.74, 127.13, 130.69, 143.72, 171.24 ppm. IR (KBr): ν˜ ϭ
3423, 2970, 1727, 1728, 1489, 1367, 1230, 1192, 1011, 888, 895
cmϪ1. MS (EI, eV): m/z (%) ϭ 619 (7) [M]ϩ, 604 (41), 547 (100),
491 (76), 435 (42), 57 (51). C19H29BrN2O4Os: calcd. C 36.83, H
4.72, N 4.52; found C 36.44, H 4.39, N 4.81.
Vinyl 1,3-Bis(tert-butyl)-2,2-dioxo-2-osma(VI)imidazolidine-4-car-
boxylate (22): This was obtained from the reaction between vinyl
acrylate (65 µL, 0.62 mmol) and the bis(imido) compound 3
(181 mg, 0.5 mmol) according to the general procedure. Purifi-
cation by column chromatography (ethyl acetate/hexanes, 1:3, v/v)
gave the title compound as a purple solid (213 mg, 0.46 mmol,
1
92%). M.p. 78 °C (dec.). H NMR (300 MHz, C6D6): δ ϭ 0.85 (s,
9 H), 0.95 (s, 9 H), 3.04 (m, J ϭ 1.0, 12.6 Hz, 1 H), 3.14 (dd, J ϭ
6.6, 12.6 Hz, 1 H), 3.81 (dd, J ϭ 1.0, 6.6 Hz,, 1 H), 4.00 (dd, J ϭ
1.7, 6.2 Hz, 1 H), 4.71 (dd, J ϭ 1.7, 13.9 Hz, 1 H), 6.94 (dd, J ϭ
6.2, 13.9 Hz, 1 H) ppm. 13C NMR (75 MHz, C6D6): δ ϭ 29.31,
29.81, 66.68, 66.76, 68.71, 74.86, 98.82, 140.78, 170.52 ppm. IR
(KBr): ν˜ ϭ 3033, 3011, 2996, 2304, 2285, 1759, 1697, 1351, 1185,
1109, 871, 860 cmϪ1. MS (EI, eV): m/z (%) ϭ 464 (20) [M]ϩ, 449
(22), 393 (100), 337 (43), 281 (59), 57 (76). HRMS: calcd. for
C13H24N2O4188Os: 460.1295; found 460.1294.
Ethyl trans-1,3-Bis(tert-butyl)-2,2-dioxo-5-phenyl-2-osma(VI)imid-
azolidine-4-carboxylate (33): This was obtained from the reaction
between ethyl cinnamate (106 mg, 0.6 mmol) and the bis(imido)
compound 3 (181 mg, 0.5 mmol) according to the general pro-
cedure. Purification by column chromatography (ethyl acetate/hex-
anes, 1:3, v/v) gave the title compound as a purple solid (255 mg,
1
0.47 mmol, 94%). M.p. 98 °C (dec.). H NMR (300 MHz, C6D6):
δ ϭ 1.05 (t, J ϭ 7.2 Hz, 3 H), 1.09 (s, 9 H), 1.19 (s, 9 H), 3.96 (q,
J ϭ 7.2 Hz, 2 H), 4.35 (s, 1 H), 5.03 (s, 1 H), 7.03Ϫ7.11 (m, 3 H),
7.30Ϫ7.36 (m, 2 H) ppm. 13C NMR (75 MHz, C6D6): δ ϭ 14.09,
29.85, 30.67, 61.37, 66.78, 67.59, 82.45, 85.40, 126.76, 128.02,
128.86, 146.21, 172.85 ppm. IR (KBr): ν˜ ϭ 3419, 2972, 1720, 1473,
1367, 1236, 1186, 1032, 908, 904, 771 cmϪ1. MS (EI, eV): m/z (%) ϭ
542 (17) [M]ϩ, 527 (15), 469 (199), 413 (83), 357 (41), 295 (54).
HRMS: calcd. for C19H30N2O4188Os: 538.1765; found 538.1767.
Osmium(VI) Azaglycolate 25: A solution of the monoimido com-
plex 2 (155 mg, 0.5 mmol) in dichloromethane under argon was
cooled to Ϫ78 °C and treated with a solution of TMEDA (90 µL,
0.58 mmol) in dichloromethane (1 mL). Solid dimethyl fumarate
(144 mg, 1.0 mmol) was added in one portion and the resulting
mixture stirred overnight while warming to room temperature. The
solvent was removed under reduced pressure and the remaining
dark-red solid purified by column chromatography (dichlorometh-
ane/methanol, 8:1, v/v) to give the title compound in the form of
two isomers as a dark-red solid (174 mg, 0.31 mmol, 61%). M.p.
Ethyl trans-1,3-Bis(tert-butyl)-5-(4Ј-nitrophenyl)-2,2-dioxo-2-osma-
(VI)imidazolidine-4-carboxylate (34): This was obtained from the re-
action between ethyl 4Ј-nitro-cinnamate (133 mg, 0.6 mmol) and
the bis(imido) compound 3 (181 mg, 0.5 mmol) according to the
general procedure. Purification by column chromatography (ethyl
acetate/hexanes, 1:3, v/v) gave the title compound as a purple solid
(249 mg, 0.42 mmol, 85%). M.p. 131 °C (dec.). 1H NMR
(300 MHz, C6D6): δ ϭ 1.02 (s, 9 H), 1.04 (t, J ϭ 7.0 Hz, 3 H), 1.08
(s, 9 H), 3.93 (q, J ϭ 7.0 Hz, 2 H), 4.12 (s, 1 H), 4.82 (s, 1 H), 7.06
(d, J ϭ 9.0 Hz, 2 H), 7.75 (d, J ϭ 9.0 Hz, 2 H) ppm. 13C NMR
(75 MHz, C6D6): δ ϭ 14.04, 29.74, 30.57, 61.70, 66.69, 67.74, 81.28,
84.92, 123.93, 127.32, 147.84, 152.43, 172.27 ppm. IR (KBr): ν˜ ϭ
3450, 2975, 2972, 1731, 1525, 1369, 1351, 1190, 901 cmϪ1. MS (EI,
eV): m/z (%) ϭ 587 (11) [M]ϩ, 572 (12), 514 (100), 458 857), 402
(43), 57 (13). HRMS: calcd. for C19H29N3O6188Os: 583.1615;
found 583.1617.
1
94 °C (dec.). H NMR (300 MHz, C6D6): δ ϭ 0.98 (s, 9 H), 1.42
(s, 9 H), 3.05 (s, 6 H), 3.17 (s, 6 H), 3.33 (s, 6 H), 3.58 (s, 1 H),
3.62 (s, 1 H), 3.64 (s, 1 H), 4.25 (s, 1 H), 5.66 (s, 2 H), 5.72 (s, 2
H) ppm. 13C NMR (75 MHz, C6D6): δ ϭ 26.57, 30.00, 30.69, 51.80,
52.15, 52.81, 56.05, 75.02, 81.27, 91.05, 97.22, 168.33, 170.12,
172.0, 173.86 ppm. IR (KBr): ν˜ ϭ 3074, 2966, 1784, 1779, 1651,
1544, 1412, 1107, 1044, 982, 781 cmϪ1. MS (EI, eV): m/z (%) ϭ 572
(100) [M]ϩ, 453 (23), 399 (18), 339 (25), 116 (43). HRMS: calcd. for
C16H33N3O7188Os: 566.9147; found 566.9152.
Diaminations of Ethyl Cinnamates with Bis(imido) Reagent 3: Di-
aminations of ethyl cinnamates were carried out following the gen-
eral procedure for diamination reactions outlined above.
Ethyl trans-1,3-Bis(tert-butyl)-5-(4Ј-methoxyphenyl)-2,2-dioxo-2-os-
ma(VI)imidazolidine-4-carboxylate (31): This was obtained from the
Details of Competitive Diamination Reactions with 3 (Hammett Cor-
reaction between ethyl 4Ј-methoxy-cinnamate (124 mg, 0.6 mmol) relation): Competition experiments were conducted with 2.5 mmol
and the bis(imido) compound 3 (181 mg, 0.5 mmol) according to
the general procedure. Purification by column chromatography
(ethyl acetate/hexanes, 1:3, v/v) gave the title compound as a purple
each of the respective 4Ј-substituted cinnamate and ethyl cinnamate
and 0.25 mmol of bis(imido) reagent 3. Ferrocene was employed as
internal standard and THF as solvent (5 mL). After a period of
solid (257 mg, 0.45 mmol, 90%). M.p. 112 °C (dec.). 1H NMR about five hours, the solvent was removed under reduced pressure
(300 MHz, C6D6): δ ϭ 1.06 (t, J ϭ 7.2 Hz, 3 H), 1.13 (s, 9 H), 1.22
(s, 9 H), 3.26 (s, 3 H), 3.95 (q, J ϭ 7.2 Hz, 2 H), 4.37 (s, 1 H), 5.04
and the crude reaction mixture was taken up in [D6]benzene and
immediately analysed by 1H NMR spectroscopy. Conversion and
(s, 1 H), 6.70 (d, J ϭ 8.8 Hz, 2 H), 7.24 (d, J ϭ 8.8 Hz, 2 H) ppm. relative product formation were calculated from the NMR spectro-
13C NMR (75 MHz, C6D6): δ ϭ 14.31, 29.93, 30.72, 54.74, 61.35,
scopic data and the kinetic expression was calculated using Equa-
66.86, 67.61, 82.03, 85.37, 114.31, 127.90, 138.11, 159.74, 172.94 tion (1).
Eur. J. Org. Chem. 2004, 2243Ϫ2252
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2249

K. Mun˜iz
FULL PAPER
127.79, 131.70, 146.99, 173.38 ppm. IR (KBr): ν˜ ϭ 2968, 2937,
2899, 1751, 1489, 1463, 1360, 1234, 1193, 1174, 1109, 1011, 868
cmϪ1. MS (EI, eV): m/z (%) ϭ 675 (13) [M]ϩ, 602 (100), 546 (22),
490 (21), 224 (12), 57 (24). HRMS: calcd. for C23H38BrN3O3188Os:
671.1655; found 671.1652.
(1)
Ethyl
[(2R,4S,5R)/(2S,4R,5S)]-trans-5-(4Ј-Bromophenyl)-1,3-bis-
(tert-butyl)-2-tert-butylimido-2-oxo-2-osma(VI)imidazolidine-4-
carboxylate (38): M.p. 68 °C (dec.). 1H NMR (300 MHz, C6D6):
δ ϭ 1.12 (t, J ϭ 7.1 Hz, 3 H), 1.17 (s, 9 H), 1.24 (s, 9 H), 1.36 (s,
9 H), 4.07 (q, J ϭ 7.1 Hz, 2 H), 4.27 (d, J ϭ 0.6 Hz, 1 H), 4.95 (s,
1 H), 6.86 (d, J ϭ 8.3 Hz, 2 H), 7.25 (d, J ϭ 8.3 Hz, 2 H) ppm.
13C NMR (75 MHz, C6D6): δ ϭ 14.27, 30.35, 31.70, 32.35, 61.03,
64.35, 64.50, 69.86, 83.50, 86.01, 121.47, 128.88, 131.14, 145.79,
174.44 ppm. IR (KBr): ν˜ ϭ 2970, 2931, 2870, 1747, 1718, 1635,
1234, 1191, 1105, 1011, 891 cmϪ1. MS (EI, eV): m/z (%) ϭ 675 (11)
[M]ϩ, 602 (100), 546 (23), 490 (29), 182 (18), 57 (18). HRMS: calcd.
for C23H38BrN3O3188Os: 671.1655; found 671.1655.
The final Hammett correlation as depicted in Figure 4 was ob-
tained employing standard sr values.[34]
Diaminations of Ethyl Cinnamates with Tris(imido) Reagent 4: Di-
aminations of ethyl cinnamates were carried out following the gen-
eral procedure for diamination reactions outlined above.
Diamination of Ethyl 4Ј-Methoxycinnamate: This reaction was car-
ried out according to the general procedure with ethyl 4Ј-methoxy-
cinnamate (72 mg, 0.3 mmol) and the tris(imido) compound 4
(105 mg, 0.25 mmol). Purification by column chromatography
(ethyl acetate/hexanes, 1:3, v/v) gave two fractions that contained
the pure diastereomers (82% combined yield, 59:41 diastereomeric
ratio).
Diamination of Ethyl Cinnamate: This was carried out with ethyl
cinnamate (53 mg, 0.3 mmol) and the tris(imido) compound 4
(105 mg, 0.25 mmol) according to the general procedure. Purifi-
cation by column chromatography (ethyl acetate/hexanes, 1:5, v/
v) gave two fractions that contained the pure diastereomers (93%
combined yield, 58:42 diastereomeric ratio).
Ethyl [(2R,4R,5S)/(2S,4S,5R)]-trans-1,3-Bis(tert-butyl)-2-tert-butyl-
imido-5-(4Ј-methyloxophenyl)-2-oxo-2-osma(VI)imidazolidine-4-
carboxylate (35): M.p. 89 °C (dec.). 1H NMR (300 MHz, C6D6):
δ ϭ 1.00 (t, J ϭ 7.1 Hz, 3 H), 1.22 (s, 9 H), 1.37 (s, 9 H), 1.60 (s,
9 H), 3.30 (s, 3 H), 3.93 (q, J ϭ 7.1 Hz, 2 H), 4.43 (s, 1 H), 5.02
(s, 1 H), 6.79Ϫ7.60 (m, 5 H) ppm. 13C NMR (75 MHz, C6D6): δ ϭ
14.11, 30.15, 32.09, 33.61, 61.29, 62.07, 65.17, 77.06, 77.94, 81.25,
84.82, 125.98, 128.43, 137.28, 142.31, 172.37 ppm. IR (KBr): ν˜ ϭ
2958, 2854, 1629, 1456, 1385, 1113, 894, 798 cmϪ1. MS (EI, eV):
m/z (%) ϭ 625 (2) [M]ϩ, 567 (3), 316 (39), 149 (62), 135 (100), 57
(97). HRMS: calcd. for C24H41N3O4188Os: 623.2656; found
623.2650.
Ethyl [(2R,4R,5S)/(2S,4S,5R)]-trans-1,3-Bis(tert-butyl)-2-tert-butyl-
imido-2-oxo-5-phenyl-2-osma(VI)imidazolidine-4-carboxylate (39):
M.p. 88 °C (dec.). 1H NMR (300 MHz, C6D6): δ ϭ 0.99 (t, J ϭ
7.2 Hz, 3 H), 1.01 (s, 9 H), 1.33 (s, 9 H), 1.59 (s, 9 H), 3.93 (q, J ϭ
7.2 Hz, 2 H), 4.43 (d, J ϭ 0.4 Hz, 1 H), 5.02 (s, 1 H), 7.02Ϫ7.22
(m, 3 H), 7.62Ϫ7.69 (m, 2 H) ppm. 13C NMR (75 MHz, C6D6):
δ ϭ 14.31, 30.52, 31.41, 32.96, 60.65, 63.92, 65.15, 69.50, 81.69,
86.78, 127.26, 127.47, 127.85, 128.56, 148.08, 173.67 ppm. IR
(KBr): ν˜ ϭ 2968, 2931, 1751, 1462, 1363, 1232, 1194, 1161, 1105,
877 cmϪ1. MS (EI, eV): m/z (%) ϭ 597 (10) [M ϩ 1]ϩ, 469 (38),
413 (52), 357 (29), 146 (22), 57 (100). HRMS: calcd. for
C23H39N3O3188Os: 593.2551; found 593.2555.
Ethyl [(2R,4S,5R)/(2S,4R,5S)]-trans-1,3-Bis(tert-butyl)-2-tert-butyl-
imido-5-(4Ј-methyloxophenyl)-2-oxo-2-osma(VI)imidazolidine-4-
carboxylate (36): M.p. 93 °C (dec.). 1H NMR (300 MHz, C6D6):
δ ϭ 1.63 (t, J ϭ 7.0 Hz, 3 H), 1.25 (s, 9 H), 1.35 (s, 9 H), 1.45 (s,
9 H), 3.31 (s, 3 H), 4.12 (q, J ϭ 7.0 Hz, 2 H), 4.45 (d, J ϭ 0.6 Hz,
1 H), 5.14 (s, 1 H), 6.75Ϫ7.42 (m, 5 H) ppm. 13C NMR (75 MHz,
C6D6): δ ϭ 15.73, 30.89, 31.06, 33.34, 60.99, 62.72, 64.09, 76.91,
78.02, 80.60, 84.34, 126.35, 128.54, 137.52, 142.11, 170.99 ppm. IR
(KBr): ν˜ ϭ 3071, 1961, 1936, 1743, 1654, 1473, 1389, 1109, 874,
802 cmϪ1. MS (EI, eV): m/z (%) ϭ 625 (1) [M]ϩ, 567 (3), 316 (23),
149 (57), 135 (88), 57 (100). HRMS: calcd. for C24H41N3O4188Os:
623.2656; found 623.2652.
Ethyl [(2R,4S,5R)/(2S,4R,5S)]-trans-1,3-Bis(tert-butyl)-2-tert-butyl-
imido-2-oxo-5-phenyl-2-osma(VI)imidazolidine-4-carboxylate (40):
M.p. 95 °C (dec.). 1H NMR (300 MHz, C6D6): δ ϭ 1.15 (t, J ϭ
7.1 Hz, 3 H), 1.21 (s, 9 H), 1.31 (s, 9 H), 1.45 (s, 9 H), 4.09 (q, J ϭ
7.1 Hz, 2 H), 4.41 (d, J ϭ 0.7 Hz, 1 H), 5.13 (s, 1 H), 7.05Ϫ7.33
(m, 5 H) ppm. 13C NMR (75 MHz, C6D6): δ ϭ 14.30, 30.42, 31.74,
32.41, 60.93, 64.45, 64.61, 69.66, 84.32, 86.25, 126.76, 127.10,
128.86, 146.74, 174.66 ppm. IR (KBr): ν˜ ϭ 3389, 2954, 2922, 1761,
1458, 1352, 1209, 1201, 1187, 1158, 1101, 1030, 876 cmϪ1. MS (EI,
eV): m/z (%) ϭ 597 (1) [M ϩ 1]ϩ, 524 (2) 469 (12), 413 (17), 355
(9), 146 (29), 57 (100). HRMS: calcd. for C23H39N3O3188Os:
593.2551; found 593.2549.
Diamination of Ethyl 4Ј-Bromocinnamate: This was carried out with
ethyl 4Ј-bromocinnamate (77 mg, 0.3 mmol) and the tris(imido)
compound 4 (105 mg, 0.25 mmol) according to the general pro-
cedure. Purification by column chromatography (ethyl acetate/hex-
anes, 1:3, v/v) gave two fractions that contained the pure dia-
stereomers (88% combined yield, 61:39 diastereomeric ratio).
Diamination of Ethyl 4Ј-Methylcinnamate: This was carried out
with ethyl 4Ј-methylcinnamate (67 mg, 0.3 mmol) and the tris(im-
ido) compound 4 (105 mg, 0.25 mmol) according to the general
procedure. Purification by column chromatography (ethyl acetate/
hexanes, 1:4, v/v) gave two fractions that contained the pure dia-
stereomers (89% combined yield, 58:42 diastereomeric ratio).
Ethyl
(tert-butyl)-2-tert-butylimido-2-oxo-2-osma(VI)imidazolidine-4- Ethyl [(2R,4R,5S)/(2S,4S,5R)]-trans-1,3-Bis(tert-butyl)-2-tert-butyl-
carboxylate (37): M.p. 64 °C (dec.). 1H NMR (300 MHz, C6D6):
imido-5-(4Ј-methylphenyl)-2-oxo-2-osma(VI)imidazolidine-4-
[(2R,4R,5S)/(2S,4S,5R)]-trans-5-(4Ј-Bromophenyl)-1,3-bis-
1
δ ϭ 0.97 (t, J ϭ 7.1 Hz, 3 H), 1.14 (s, 9 H), 1.27 (s, 9 H), 1.57 (s, carboxylate (41): M.p. 101 °C (dec.). H NMR (300 MHz, C6D6):
9 H), 3.89 (q, J ϭ 7.1 Hz, 1 H), 3.90 (q, J ϭ 7.1 Hz, 1 H), 4.28 (s, δ ϭ 0.98 (t, J ϭ 7.0 Hz, 3 H), 1.21 (s, 9 H), 1.35 (s, 9 H), 1.59 (s,
1 H), 4.83 (s, 1 H), 7.29 (d, J ϭ 7.9 Hz, 2 H), 7.30 (d, J ϭ 7.9 Hz, 9 H), 3.91 (q, J ϭ 7.0 Hz, 2 H), 4.45 (d, J ϭ 0.4 Hz, 1 H), 5.04 (s,
2 H) ppm. 13C NMR (75 MHz, C6D6): δ ϭ 14.29, 30.47, 31.37, 1 H), 7.04 (d, J ϭ 7.9 Hz, 2 H), 7.10Ϫ7.18 (m, 2 H) ppm. 13C NMR
32.88, 60.75, 63.83, 65.05, 69.67, 80.89, 86.44, 121.43, 129.08, (75 MHz, C6D6): δ ϭ 14.32, 21.02, 30.54, 31.46, 33.00, 60.63, 63.94,
2250
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 2243Ϫ2252

Electronic Effects in Olefin Oxidation by Imidoosmium(VIII) Compounds
65.19, 69.46, 81.58, 86.82, 127.25, 129.29, 136.83, 145.20, 173.75
FULL PAPER
Acknowledgments
ppm. IR (KBr): ν˜ ϭ 2968, 2924, 2864, 1747, 1647, 1464, 1363,
1236, 1185, 1107, 1028, 872 cmϪ1. MS (EI, eV): m/z (%) ϭ 611 (20)
[M ϩ 1]ϩ, 596 (11), 538 (100), 482 (20), 426 (17), 160 (22), 57 (24).
HRMS: calcd. for C24H41N3O3188Os: 607.2707; found 607.2714.
The author is grateful to Professor K. H. Dötz for his continuing
support and interest. This work was supported by the Fonds der
Chemischen Industrie (Liebig Fellowship to K. M.). The author
thanks Mr. A. Iesato, Hokkaido/Japan, for an initial experimental
contribution and Ms. Ulrike Weynand for some NMR measure-
ments.
Ethyl [(2R,4S,5R)/(2S,4R,5S)]-trans-1,3-Bis(tert-butyl)-2-tert-butyl-
imido-5-(4Ј-methylphenyl)-2-oxo-2-osma(VI)imidazolidine-4-
carboxylate (42): M.p. 94 °C (dec.). 1H NMR (300 MHz, C6D6):
δ ϭ 1.15 (t, J ϭ 7.0 Hz, 3 H), 1.24 (s, 9 H), 1.33 (s, 9 H), 1.47 (s,
9 H), 4.09 (q, J ϭ 7.0 Hz, 2 H), 4.44 (d, J ϭ 0.4 Hz, 1 H), 5.14 (s,
1 H), 7.03Ϫ7.11 (m, 2 H), 7.22Ϫ7.28 (m, 2 H) ppm. 13C NMR
(75 MHz, C6D6): δ ϭ 14.44, 25.06, 30.47, 31.79, 32.46, 61.09, 64.22,
64.94, 69.46, 75.53, 82.28, 84.69, 126.83, 129.47, 133.73, 145.65,
174.01 ppm. IR (KBr): ν˜ ϭ 2654, 2931, 1756, 1471, 1226, 1100,
1033, 873 cmϪ1. MS (EI, eV): m/z (%) ϭ 611 [M ϩ 1]ϩ(18), 596
(10), 538 (100), 482 (23), 426 (16), 160 (21), 57 (20). HRMS: calcd.
for C24H41N3O3188Os: 607.2707; found 607.2702.
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[3]
[4]
Diamination of Ethyl 4-Nitrocinnamate: This was carried out with
ethyl 4Ј-nitrocinnamate (67 mg, 0.3 mmol) and tris(imido) com-
pound 4 (105 mg, 0.25 mmol) according to the general procedure.
Purification by column chromatography (ethyl acetate/hexanes, 1:4,
v/v) gave two fractions that contained the pure diastereomers (96%
combined yield, 68:32 diastereomeric ratio).
[5]
Ethyl [(2R,4R,5S)/(2S,4S,5R)]-trans-1,3-Bis(tert-butyl)-2-tert-butyl-
imido-5-(4Ј-nitrophenyl)-2-oxo-2-osma(VI)imidazolidine-4-
carboxylate (42): M.p. 86 °C (dec.). 1H NMR (300 MHz, C6D6):
δ ϭ 0.98 (t, J ϭ 7.2 Hz, 3 H), 1.22 (s, 9 H), 1.43 (s, 9 H), 1.56 (s,
9 H), 3.92 (q, J ϭ 7.2 Hz, 2 H), 4.18 (d, J ϭ 0.5 Hz, 1 H), 4.81 (s,
1 H), 7.87 (d, J ϭ 7.5 Hz, 2 H), 7.88 (d, J ϭ 7.5 Hz, 2 H) ppm.
13C NMR (75 MHz, C6D6): δ ϭ 14.27, 30.43, 31.31, 32.78, 60.97,
63.73, 64.98, 69.94, 80.73, 86.26, 123.68, 127.48, 127.79, 128.11,
154.67, 173.04 ppm. IR (KBr): ν˜ ϭ 2968, 2866, 1753, 1525, 1344,
1230, 1191, 1109, 872, 858 cmϪ1. MS (EI, eV): m/z (%) ϭ 642 (20)
[M ϩ 1]ϩ, 627 (18), 569 (100), 513 (22), 457 (27), 191 (20), 57 (16).
HRMS: calcd. for C23H38N4O5188Os: 638.2401; found 638.2400.
[6]
J. A. Bodkin, M. D. McLeod, J. Chem. Soc., Perkin Trans. 1
2002, 2733.
[7]
K. B. Sharpless, Angew. Chem. 2002, 114, 2126; Angew. Chem.
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D. J. Berrisford, C. Bolm, K. B. Sharpless, Angew. Chem. 1995,
107, 1159; Angew. Chem. Int. Ed. Engl. 1995, 34, 1059.
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General review on Os-imido compounds: K. Mun˜iz, Chem.
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[10]
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Ethyl [(2R,4S,5R)/(2S,4R,5S)]-trans-1,3-Bis(tert-butyl)-2-tert-butyl-
imido-5-(4Ј-nitrophenyl)-2-oxo-2-osma(VI)imidazolidine-4-
carboxylate (43): M.p. 78 °C (dec.). 1H NMR (300 MHz, C6D6):
δ ϭ 1.13 (t, J ϭ 6.7 Hz, 3 H), 1.14 (s, 9 H), 1.20 (s, 9 H), 1.33 (s,
9 H), 4.09 (q, J ϭ 7.2 Hz, 2 H), 4.18 (s, 1 H), 4.92 (s, 1 H), 6.95
(d, J ϭ 8.6 Hz, 2 H), 7.88 (d, J ϭ 8.6 Hz, 2 H) ppm. 13C NMR
(75 MHz, C6D6): δ ϭ 14.24, 30.28, 31.64, 32.27, 53.25, 61.25, 64.25,
64.40, 83.27, 85.92, 123.12, 127.90, 128.02, 128.10, 153.56, 174.15
ppm. IR (KBr): ν˜ ϭ 3437, 2972, 2929, 1743, 1524, 1344, 1191,
1081, 881 cmϪ1. MS (EI, eV): m/z (%) ϭ 642 (11) [M ϩ 1]ϩ, 569
(100), 513 (20), 457 (21), 191 (18), 57 (33). HRMS: calcd. for
C23H38N4O5188Os: 638.2401; found 638.2407.
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Reproduction of selected NMR spectra can be found in the
Supporting Information (for Supporting Information see also
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Details of Competitive Diamination Reactions with 4 (Hammett Cor-
relation): Competition experiments were conducted with 2.5 mmol
each of the respective 4Ј-substituted cinnamate and ethyl cinnamate
and 0.25 mmol of tris(imido) reagent 4. Ferrocene was employed
as internal standard and THF as solvent (5 mL). After a period of
about five hours, the solvent was removed under reduced pressure
and the crude reaction mixture was taken up in [D6]benzene and
immediately analysed by 1H NMR spectroscopy. Conversion and
relative product formation were calculated from the NMR spectro-
scopic data using the respective dr values as determined from the
individual diaminations detailed above and the kinetic expression
was calculated using the following Equation (1).
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The final Hammett correlation as depicted in Figure 5 was ob-
tained employing standard σx values.[34]
Eur. J. Org. Chem. 2004, 2243Ϫ2252
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2251

K. Mun˜iz
FULL PAPER
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Details on the formation of the stereogenic metal centres are
discussed in ref.[16] A relative [(2R,4R,5S)/(2S,4S,5R)]-configu-
ration for the major diastereomers was assigned by X-ray
analysis of the major diastereomer obtained from diamination
of methyl cinnamate with compound 4. Details of this crystal
structure analysis will be published elsewhere.
[32]
[33]
[34]
2252
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 2243Ϫ2252