Dearomatization of naphthalene: Stereoselective cis-1,4 tandem additions promoted by osmium(II)

Article abstract of DOI:10.1021/ja980624t

The naphthalene complex of pentaammineosmium(II) (1) reacts with four different classes of electrophiles to form 1-naphthalenium species 2-5. These η³-allyl complexes react stereospecifically with a variety of nucleophiles to form cis-1,4-dihydronaphthalene complexes. The entire reaction sequence may be performed outside a glovebox in two steps using conventional techniques.

Full text of DOI:10.1021/ja980624t

J. Am. Chem. Soc. 1998, 120, 7835-7840
7835
Dearomatization of Naphthalene: Stereoselective cis-1,4 Tandem
Additions Promoted by Osmium(II)
Mark D. Winemiller and W. Dean Harman*
Contribution from the Department of Chemistry, UniVersity of Virginia, CharlottesVille, Virginia 22901
ReceiVed February 24, 1998
Abstract: The naphthalene complex of pentaammineosmium(II) (1) reacts with four different classes of
electrophiles to form 1-naphthalenium species 2-5. These η3-allyl complexes react stereospecifically with a
variety of nucleophiles to form cis-1,4-dihydronaphthalene complexes. The entire reaction sequence may be
performed outside a glovebox in two steps using conventional techniques.
Introduction
Given the abundance of compounds in nature that contain
dihydronaphthalene or tetralin cores, efficient methods for the
preparation of these materials are highly desirable.1-3 Proce-
dures that generate functionalized dihydronaphthalenes directly
from their aromatic precursors have become valuable tools to
the synthetic chemist, due to the availability and stability of
naphthalene and substituted naphthalenes. For many years, the
Birch reduction has been the primary synthetic method to
achieve this transformation,4 yet this reaction has limitations.
Only hydrogen and unfunctionalized alkyl groups can be
introduced during the dearomatization, and the reaction condi-
tions are incompatible with many functional groups. Regiose-
lectivity is often poor, and over-reduction is a common problem.
Although recent modifications of the Birch reduction such as
the use of silylated naphthalenes expand its utility,5,6 regio- and
stereocontrol can still be problematic.
Our interest in the ability of pentaammineosmium(II) to
activate aromatic systems toward electrophilic additions7 led
us to consider the possibility of generating dihydronaphthalenes
by a pathway involving a sequential addition of an electrophile
and a nucleophile. The naphthalene complex [Os(NH3)5(η2-
naphthalene)](OTf)2 (1) is readily protonated with triflic acid
(HOTf) in acetonitrile (CH3CN), and the acidity of the resulting
1-naphthalenium species (pKa ) -8.2) is considerably weaker
than that of the organic naphthalenium ion.8 We now report
that the introduction of carbon-based electrophiles generates a
series of naphthalenium complexes that react with nonbasic
nucleophiles to generate stable dihydronaphthalene complexes
from which the modified organic ligands can be extracted.
Figure 1. Electrophilic addition reactions of [Os(NH3)5(η2-naphtha-
lene)](OTf)2 (1).
Results
The naphthalene complex of pentaammineosmium(II) (1)
reacts with triflic acid (HOTf) to generate a solution-stable allyl
species, 2 (Figure 1). At ambient temperatures this species
slowly decomposes, liberating free naphthalene in the process,
but at -40 °C in CH3CN 2 is stable for days.8 Although
complex 2 is considerably less acidic than its organic counter-
part, we found that most nucleophiles reacted as bases with 2
to regenerate compound 1 quantitatively. However, the weak
hydride donor triethylsilane reacted with a solution of naph-
thalenium 2 at 20 °C to form the dihydronaphthalene complex
2a in a 93% yield (Figure 2). The organic ligand was
decomplexed using silver triflate (AgOTf) under mildly basic
conditions to yield 1,4-dihydronaphthalene (2a′) in 60% yield,
56% overall from naphthalene (Figure 2). 1-Methoxy-2-methyl-
1-(trimethylsiloxy)propene (MMTP) also underwent clean ad-
dition to C4 with the 1-naphthalenium complex 2 at -40 °C.
The product, 2b, was then oxidized with AgOTf in a H2O/CH3-
CN/ether solution, and the organic product was isolated.
(1) Castro, M. A.; Gordaliza, M.; Del Corral, J. M. M.; Feliciano, A. S.
Phytochemistry 1996, 41, 995-1011.
(2) Ward, R. S. Nat. Prod. ReV. 1997, 14, 43-74.
(3) Go¨zler, T.; Go¨zler, B.; Patra, A.; Leet, J. E.; Freyer, A. J.; Shamma,
M. Tetrahedron 1984, 40, 1145-1150.
(4) Rabideau, P. W.; Marcinow, Z. Organic Reactions; John Wiley &
Sons Inc.: New York, 1992; Vol. 42.
(5) Rabideau, P. W.; Karrick, G. L. Tetrahedron Lett. 1987, 28, 2481-
2484.
(6) Marcinow, Z.; Clawson, D. K.; Rabideau, P. W. Tetrahedron 1989,
45, 5441-5448.
(7) Harman, W. D. Chem. ReV. 1997, 97, 1953.
(8) Winemiller, W. D.; Kopach, M. E.; Harman, W. D. J. Am. Chem.
Soc. 1997, 119, 2096.
S0002-7863(98)00624-6 CCC: $15.00 © 1998 American Chemical Society
Published on Web 07/23/1998

7836 J. Am. Chem. Soc., Vol. 120, No. 31, 1998
Winemiller and Harman
Table 1. Overall Yields for the Tandem Addition to Naphthalene
Figure 2. Protonation followed by nucleophilic addition to form 1,4-
dihydronaphthalene complexes.
Repeating these steps without isolation of complex 2b or
purification of any intermediate resulted in an oVerall 77% yield
of the dihydronaphthalene 2b′ (purified, isolated).
Three distinct classes of carbon electrophiles were success-
fully added to the naphthalene complex 1. The addition of an
acetal, dimethoxymethane, was performed at 20 °C in CH3CN
using HOTf to promote the reaction. After precipitation from
diethyl ether, the 1-naphthalenium species 3 was isolated in 88%
yield as an analytically pure triflate salt (see Figure 1). The
1H and 13C NMR spectra of 3 are overall very similar to those
of the parent naphthalenium complex 2. Three carbon signals
at 86.3, 82.4, and 76.4 ppm as well as proton signals at 6.41,
6.13, and 5.52 ppm in CD3CN confirm η3 coordination of the
ligand.8 A singlet at 3.30 ppm in the 1H NMR spectrum and a
methylene carbon signal at 73.8 ppm in the 13C NMR spectrum
further support the assignment of 3 as that shown in Figure 1.
In the presence of HOTf in CH3CN, the Michael acceptor methyl
vinyl ketone (MVK) reacted in a 1,4 fashion with the naphtha-
lene complex 1 to generate the naphthalenium species 4 (see
Figure 1; 90% yield). Complex 4 was precipitated as a triflate
salt in analytically pure form from diethyl ether. Spectral
features of 4 are similar to the naphthalenium 3 but include
two methylene carbons at 38.9 and 28.5 ppm in the 13C NMR
spectrum and a singlet at 2.05 ppm in the 1H spectrum
supporting the assignment shown in Figure 1. Tertiary alcohols
also react with the naphthalene complex 1 to form a stable
1-naphthalenium species. For example, when a solution of 1
and tert-butyl alcohol in CH3CN was treated with triflic
anhydride, the allyl 5 (see Figure 1) formed in 75% yield. 1H
and 13C NMR spectra revealed three allyl carbons at 88.0, 86.2,
and 77.1 ppm, and their corresponding protons appeared at 6.42,
6.20, and 5.77 ppm (CD3CN). In addition, a large singlet at
1.08 ppm (9H) in the 1H NMR spectrum confirmed the presence
of a tert-butyl group.
The presence of a carbon substituent at C1 anti to the metal
(vide infra) greatly increases the range of nucleophiles capable
of reacting successfully with the η3-1-naphthalenium complexes
(Figure 3). The scope of nucleophilic addition was investigated
using the methoxymethyl naphthalenium complex 3. In a typical
reaction procedure, complex 3 was dissolved in CH3CN, and
the solution was cooled to -40 °C. Once thermally equilibrated,
the allyl solution was added to a chilled solution of nucleophile
(-40 °C). After allowing enough time for the nucleophile to
react, the complexes were precipitated using a diethyl ether/
CH2Cl2 mixture. All of the complexes in Figure 3 were isolated
as triflate salts with yields varying greatly as a result of
incomplete precipitation. The main 1H and 13C NMR spectral
features shared by the 1,4-dihydronaphthalene complexes in
acetone-d6 were bound olefin protons shifted upfield by at least
1 ppm and carbon signals for the bound olefin between 55.0
and 45.0 ppm.
The difficulties encountered in precipitating many of the
dihydronaphthalene complexes (3a-f) prompted us to bypass
the isolation of these intermediate dihydronaphthalene com-
plexes. Instead, nucleophilic addition was immediately followed
by oxidative decomplexation, and the organic product was
isolated directly. After the addition of the nucleophile, oxidation
of the 1,4-dihydronaphthalene complex was accomplished with
the addition of AgOTf. The 1,4-dihydronaphthalene complex
solution was first warmed to 20 °C and added to a H2O/ether
solution, then AgOTf was added. At the end of 0.5 h, the
reaction mixture was heated in a sealed tube. The resulting
1,4-dihydronaphthalene products were obtained after chroma-
tography in overall yields typically in the range of 40-75%.
The organic compounds reported in Table 1 were highly air-
sensitive in their concentrated form and decomposed in periods
as brief as 15-20 min. Thus, the products were frozen in a
benzene matrix immediately after chromatography. The yields
reported in Table 1 represent isolated yields of a single
stereoisomer of the dihydronaphthalene, determined for the four-
step reaction sequence. These yields reflect an average yield
per chemical step of 80-93%.
The naphthalenium complexes 4 and 5 were also reactive
with nucleophiles, and a stabilized enolate was used as an
example (Figure 4). The reaction conditions required to form
5 were not compatible with the adaptation of a tandem process,
thus complex 5 was first isolated as its triflate salt then
redissolved in CH3CN, where it was treated with dimethyl
malonate and base. The reaction mixture was then treated with
AgOTf, and the organic product 5a′ was isolated and purified.

Dearomatization of Naphthalene
J. Am. Chem. Soc., Vol. 120, No. 31, 1998 7837
Figure 3. Nucleophilic addition reactions of the η3-1-naphthalenium complex 3.
rarely >6.1-6.2 ppm.9-11 This is consistent with the observa-
tions for our reported compounds. For 1,2-dihydronaphthalenes
the R proton is shifted to considerably lower field, usually >6.5
ppm.3,12
The stereochemistry of the reported 1,4-dihydronaphthalenes
1
was confirmed by analysis of H NMR coupling data for the
isolated complexes and their organic ligands. In every case
examined, the coordinated olefinic protons are doublets. The
lack of additional splitting indicates that the incoming
Figure 4. Nucleophilic addition reactions of the η3-1-naphthalenium
complexes 4 and 5.
This protocol reduced the overall yield of the organic ligand
(5a′) to 25% as a result of the low efficiency of the precipitation
process.
(9) Rabideau, P. W.; Burkholder, E. G. J. Org. Chem. 1979, 44, 2354-
2357.
(10) Rabideau, P. W.; Husted, C. A.; Young, D. M. J. Org. Chem. 1983,
48, 4149-5150.
(11) Rabideau, P. W. The Conformational Analysis of Cyclohexenes,
Cyclohexadienes, and Related Hydroaromatic Compounds; VCH Publishers
Inc.: New York, 1989.
(12) Robichaud, A. J.; Meyers, A. I. J. Org. Chem. 1991, 56, 2607-
2609.
The regiochemistry of the addition reaction was confirmed
by comparison of the two vinyl protons in the organic products
with values reported in the literature. The olefinic protons of
1,4-dihydronaphthalenes have chemical shifts that typically
1
differ by less that 0.2 ppm in the H NMR spectrum and are

7838 J. Am. Chem. Soc., Vol. 120, No. 31, 1998
Winemiller and Harman
substituents add to the ring face opposite to that of metal
coordination, thereby creating dihedral angles of approximately
90° for H1-C1-C2-H2 and for H3-C3-C4-H4, consistent
with a coupling constant close to 0 Hz.
The entire synthetic sequence outlined above, including the
complexation of naphthalene, may be performed outside the
glovebox without the aid of specialized glassware. We em-
ployed freshly activated magnesium stored under nitrogen, but
otherwise, no special precautions were taken to purify or degas
reagents. After complexation, the η2-naphthalene complex was
isolated then used immediately. As an example, the dihy-
dronaphthalene 3a′ was prepared on the bench in overall 50%
yield from naphthalene taking no precautions to dry solvents
or glassware. This represents only a modest drop in yield
compared to a 65% yield obtained using rigorously purified
materials.
In a manner similar to naphthalene, anthracene and phenan-
threne13 form a stable complex with osmium(II) in which the
metal binds across C1 and C2. Unlike the reactivity traditional
observed for anthracene, chemistry takes place exclusively on
the terminal ring.8 The pKa for the 1-anthracenium complex
of pentaammineosmium(II) (-8.0) is close to that of the
1-naphthalenium complex,8 and our preliminary data indicate
that addition of MVK occurs at C1 to generate a 1-anthracenium
species analogous to 4. Subsequent treatment with the nucleo-
phile MMTP generates a 1,4-dihydroanthracene complex in
good yield.
Figure 5. Resonance structure interpretation of 1,4 versus 1,2 addition.
Discussion
The 1,4-dihydronaphthalene skeleton is present in numerous
natural products and is particularly prevalent in the lignanoid
family.1-3 The dearomatization methodology outlined herein
provides a method for the rapid formation of cis-1,4-disubsti-
tuted naphthalenes from aromatic precursors. The diversity of
substituents incorporated by this process is considerably broader
than has been realized using the Birch process.4 Consider for
example the tricyclic lignanoid core 3f ′ (Table 1), found in the
natural products such as phyltetralin,14 podophyllotoxin, or
etoposide.1 This material can be generated as a single regio-
and stereoisomer from naphthalene, an acetal, and phenyllithium
with an overall yield of 40%.
The pentaammineosmium(II) fragment functions by adding
electron density into the ligand π system through π back-
bonding. As a consequence, electrophilic rather than nucleo-
philic addition occurs, contrary to what is usually observed for
metal-mediated reactions with arenes15 or naphthayloxazo-
lines.12,14,16 The site of the initial electrophilic addition is
governed by the thermodynamic preference of the metal for
binding across C1 and C2.8,13 The observation that the
nucleophilic addition occurs predominantly in a 1,4 manner is
rationalized in Figure 5. In consideration of the two resonance
structures that place a positive charge on a terminal carbon of
the allyl system (I and III), only III allows further delocalization
into the aromatic ring. Thus, the osmium is likely to be closer
to C2 than to C4, and addition is kinetically favored at the latter
carbon. Verification of this distortion in the bonding of the
naphthalenium system using X-ray diffraction has been frus-
trated by difficulties in obtaining a suitable single crystal of
the reactive 1-naphthalenium complexes, but similar distortions
Figure 6. Molecular model showing kinetic stabilization against
deprotonation at C1 of the η3-naphthalenium complex (4).
in π-allyl complexes have been documented.17,18 The observed
cis stereochemistry is again a direct result of the metal, but in
this case steric influences control the addition. The metal
efffectively blocks one face of the naphthalene ligand, forcing
attack of both electrophile and nucleophile to occur from the
opposite face. The steric bulk of the metal also plays an
important role in protecting the acidic proton at C1 of the
1-naphthalenium complexes (Figure 6). Correspondingly, al-
though the pKa of the C1 proton rivals that of strong mineral
acids, clean 1,4-addition is possible even with nucleophiles as
basic as malonate anions.
Conclusion
A new methodology for synthesizing cis-1,4-dihydronaph-
thalenes in good yields directly from naphthalene has been
developed. This dearomatization procedure takes advantage of
(13) Winemiller, M. D.; Kelsch, B. A.; Sabat, M.; Harman, W. D.
Organometallics 1997, 16, 3672.
(14) Meyers, A. I.; Roth, G. P.; Hoyer, D.; Barner, B. A.; Laucher, D.
J. Am. Chem. Soc. 1988, 110, 4611-4624.
(15) Ku¨ndig, E. P. Pure Appl. Chem. 1985, 57, 1855-1864.
(16) Shimano, M.; Meyers, A. I. J. Org. Chem. 1995, 60, 7445.
(17) Beers, O. C. P.; Elsevier: C. J.; Ernsting, J.-M. Organometallics
1992, 11, 3886.
(18) Johnson, J. R.; Tully, P. S.; Mackenzie, P. B.; Sabat, M. J. Am.
Chem. Soc. 1991, 113, 6172.

Dearomatization of Naphthalene
J. Am. Chem. Soc., Vol. 120, No. 31, 1998 7839
butyl alcohol (297 mg, 4.02 mmol) in 1.91 g of CH3CN, which was
then treated with a solution of triflic anhydride (941 mg, 3.35 mmol)
in 1.90 g of CH3CN. After 2 h, the solution was precipitated into ether
and filtered to yield 5, 347 mg (0.38 mmol, 75%). 1H NMR (300 MHz,
CD3CN): δ 7.54 (d, J ) 7.5 Hz, 1H), 7.38 (td, J ) 7.2, 1.5 Hz, 1H),
7.28 (dd, J ) 7.5, 1.2 Hz, 1H), 7.38 (td, J ) 7.5, 1.5 Hz, 1H), 6.42
(dd, J ) 6.0, 2.4 Hz, 1H), 6.20 (m, 1H), 5.77 (t, J ) 6.1 Hz, 1H), 5.28
the electron-donating properties of pentaammineosmium(II) to
promote electrophilic addition to C1 and to stabilize the
1-naphthalenium products such that a carbon-based nucleophile
may be added. This process does not require use of any
specialized glassware.
Experimental Details
(br s, 3H), 3.82 (br s, 12H), 2.25 (d, J ) 3.0 Hz, 1H), 1.08 (s, 9H). 13
C
General Procedure. 1H and 13C NMR spectra were recorded on a
General Electric GN-300 spectrometer unless otherwise noted. Chemi-
cal shifts are reported in parts per million relative to TMS (δ CD3CN
) 1.93, acetone-d6 ) 2.04, CDCl3 ) 7.26, CD3OD ) 3.30). 2D-NMR
experiments (DEPT, NOE) were recorded on a General Electric GN-
300 spectrometer as well. 13C multiplicities are supported by DEPT
data. Electrochemical experiments were performed under nitrogen
using a PAR model 362 potentiostat driven by a PAR model 175
universal programmer. Cyclic voltammograms were recorded (Kipp
& Zonen BD90 XY recorder) in a standard three-electrode cell, from
+1.7 to -1.7 V with a glassy carbon electrode. All potentials are
reported vs NHE and, unless otherwise noted, were determined in
NMR (75 MHz, CD3CN): δ 133.7 (C), 133.0 (C), 132.6 (CH), 131.9
(CH), 131.7 (CH), 130.1 (CH), 88.0 (CH), 86.2 (CH), 77.1 (CH), 50.6
(CH), 35.0 (C), 28.8 (CH3).
[Os(NH3)5(2,3-η2-1,4-dihydronaphthalene)](OTf)2 (2a). Complex
1 (90 mg, 0.13 mmol) was dissolved in a solution of HOTf (397 mg,
2.64 mmol) in 1.02 g of CH3CN and stirred. The stirring solution was
then treated with a solution of triethylsilane (404 mg, 3.49 mmol) in
950 mg of CH3CN. The stirring was continued for 0.5 h, and the
solution was precipitated into ether and filtered to yield 2a (85 mg,
0.12 mmol, 93%). 1H NMR (300 MHz, CD3CN): δ 7.08 (m, 4H),
4.18 (d, J ) 19.8 Hz, 2H), 3.91 (br, s, 3H), 3.69 (s, 2H), 2.93 (d, J )
19.8 Hz), 2.75 (br, s, 12H).
acetonitrile (about 0.5 M TBAH) at 100 mV/s using cobaltocene (E1/2
)
1,4-Dihydronaphthalene (2a′). Complex 2a was dissolved in a
solution of diisopropylethylamine (DIEA) (45 mg, 0.35 mmol) in 3.0
g of CH3CN. To this solution was added AgOTf (214 mg, 0.83 mmol)
and vigorous stirring was started. At the end of 0.5 h, the solution
was transferred to a pressure tube and heated at 80 °C for another 0.5
h. The solution was cooled and added to stirring ether, followed by
filtration of all precipitates. The ether was removed, and column
chromatography of the product using hexanes yielded 41 mg of 2a′
(0.32 mmol, 60%). 1H NMR (300 MHz, CDCl3): δ 7.14 (br, s, 4H),
6.01 (br, s, 2H), 3.41 (br, s, 4H). 13C NMR (75 MHz, CDCl3): δ
135.3 (C), 129.7 (CH), 126.6 (CH), 125.6 (CH), 30.9 (CH2).
-0.78 V) in situ as a calibration standard. The peak-to-peak separation
(Ep,a - Ep,c) was between 80 and 100 mV for all reversible couples
unless otherwise noted. Some of this work was carried out under a
nitrogen atmosphere in a Vacuum Atmospheres Co. glovebox.
Solvents. Acetonitrile-d3 (Cambridge Isotope Labs) was refluxed
over CaH2 and distilled under argon. Acetone-d6 (Cambridge Isotope
Labs) was used as received except that it was deoxygenated prior to
use. Methanol-d4 (Cambridge Isotope Labs) was received in sealed
ampules and used without any further purification, as was chloroform-d
(Cambridge Isotope Labs).
Reagents. The precursor, [Os(NH3)5OTf](OTf)2, was synthesized
as earlier described.8 Dimethoxymethane was dried over sodium and
distilled under argon, methyl vinyl ketone was distilled under vacuum,
and tert-butyl alcohol was dried over CaH2 then distilled under argon.
All other reagents were used as received. Both the complexes 1 and
2 were previously reported.8
[Os(NH3)5(2,3,4-η3-1-methoxymethyl-1H-naphthalenium)}]-
(OTf)3 (3). Complex 1 (929 mg, 1.33 mmol) was dissolved in a
solution of dimethoxymethane (268 mg, 3.53 mmol) in 2.50 g of CH3-
CN, which was then treated with a solution of HOTf (416 mg, 2.78
mmol) in 2.50 g of CH3CN. After 1 h, the solution was precipitated
into ether and filtered through a fine frit to yield 3, 1.04 g (1.16 mmol,
88%). 1H NMR (300 MHz, CD3CN): δ 7.58 (d, J ) 6.6 Hz, 1H),
7.35 (m, 3H), 6.41 (dd, J ) 6.0, 2.1 Hz, 1H), 6.13 (m, 1H), 5.52 (t, J
) 6.3 Hz, 1H), 5.29 (br s, 3H), 4.08-3.98 (m, 2H), 3.89 (br s, 12H),
3.30 (s, 3H), 2.31 (m,1H). 13C NMR (75 MHz, CD3CN): δ 133.2
(C), 132.7 (C), 132.3 (CH), 131.4 (CH), 130.6 (CH), 129.2 (CH), 86.3
(CH), 82.4 (CH), 76.4 (CH), 73.8 (CH2), 59.3 (CH3), 41.7 (CH). Anal.
Calcd for C15H28N5O10S3F9Os: C, 20.11; H, 3.21; N, 7.82. Found:
C, 19.77; H, 3.37; N, 8.03.
[Os(NH3)5{2,3-η2-(1-(2′-(2′-carbomethoxy)propyl)-1,4-dihydro-
naphthalene)}](OTf)2 (2b). 1H NMR (300 MHz, CD3OD): δ 7.13
(m, 4H), 4.30 (dd, J ) 18.9, 3.6 Hz, 1H), 4.29 (br s, 3H), 3.76 (s, 3H),
3.65 (dd, J ) 9.0, 3.6 Hz, 1H), 3.43 (s, 1H), 3.36 (d, J ) 9.0 Hz, 1H),
3.02 (br, s, 12H), 2.91 (d, J ) 18.9, 1H), 1.26 (s, 3H), 1.24 (s, 3H).
13C NMR (75 MHz, acetone-d6): δ 178.4 (C), 137.8 (C), 136.2 (C),
131.6 (CH), 129.5 (CH), 127.5 (CH), 126.0 (CH), 52.3 (C), 51.8 (CH3),
50.8 (CH), 49.1 (CH), 48.9 (CH), 32.3 (CH2), 25.2 (CH3), 20.3 (CH3).
Cyclic voltammetry: Ep,a ) 0.68 V.
1-(2′-(2′-Carbomethoxy)propyl)-1,4-dihydronaphthalene (2b′).
Complex 1 (402 mg, 0.57 mmol) was dissolved in a solution of HOTf
(430 mg, 2.86 mmol) in 1.09 g of CH3CN and cooled to -40 °C, then
added to another -40 °C solution of methyl trimethylsilyl dimethyl-
ketene acetal (714 mg, 4.10 mmol) in 1.10 g of CH3CN and allowed
to react for an additional 10 min at -40 °C. The solution was warmed
to room temperature and added to 5 mL of H2O that contained HOTf
(108 mg, 0.72 mmol). Diethyl ether (5 mL) was added, and the solution
was stirred rapidly. To this rapidly stirring solution was added AgOTf
(319 mg, 1.24 mmol), and stirring was continued for 0.5 h, after which
time the entire solution was transferred to a pressure tube and heated
at 80 °C for another 0.5 h. After cooling, the solution was extracted
with ether and column chromatography on silica gel (200 mL of 5%
ether/petroleum ether, 100 mL of 10% ether/petroleum ether, then 20%
ether/petroleum ether until completion) yielded 102 mg of 2b′, (0.45
mmol, 77%). 1H NMR (300 MHz, CDCl3): δ 7.20-7.07 (m, 4H),
6.18 (dd, J ) 9.9, 2.4 Hz, 1H), 5.95 (m,1H), 3.86 (m, 1H), 3.73 (s,
3H), 3.44 (m, 1H), 3.26 (dd, J ) 16.2, 2.1 Hz, 1H), 1.08 (s, 3H), 1.07
(s, 3H). 13C NMR (75 MHz, CDCl3): δ 177.8 (C), 136.5 (C), 135.1
(C), 128.9 (CH), 128.4 (CH), 128.1 (CH), 126.7 (CH), 126.1 (CH),
125.3 (CH), 51.7 (CH), 50.0 (C), 47.1 (CH), 31.1 (CH2), 22.1 (CH3),
21.4 (CH3).
[Os(NH3)5(2,3,4-η3-{1-(3′-oxobutyl)-1H-naphthalenium)}]-
(OTf)3 (4). To a stirring solution of 1 (535 mg, 0.76 mmol) dissolved
in 3.52 g of CH3CN was added dropwise a solution of MVK (70 mg,
1.00 mmol) in 530 mg of CH3CN, followed by HOTf (126 mg, 0.84
mmol) in 500 mg of CH3CN. The solution was stirred rapidly for 15
min, and then, to ensure completion, a solution of MVK (39 mg, 0.56
mmol) in 500 mg of CH3CN was added, followed by a solution of
HOTf (31 mg, 0.21 mmol) in 500 mg of CH3CN. Stirring was
continued for an additional 15 min, and the product was precipitated
in diethyl ether to yield 4 (633 mg, 0.69 mmol, 90%). 1H NMR (300
MHz, CD3CN): δ 7.57 (d, J ) 6.3 Hz, 1H), 7.35 (m, 3H), 6.42 (dd,
J ) 5.7, 1.8 Hz, 1H), 6.04 (m, 1H), 5.50 (t, J ) 6.6 Hz, 1H), 5.27 (br,
s, 3H), 3.85 (br, s, 12H), 2.65-2.20 (m, 5H), 2.05 (s, 3H). 13C NMR
(75 MHz, acetone-d6): δ 207.3 (C), 135.1 (C), 132.7 (C), 131.7 (CH),
130.7 (CH), 129.8 (CH), 128.2 (CH), 84.6 (CH), 83.4 (CH), 75.6 (CH),
39.0 (CH), 38.9 (CH2), 29.5 (CH3), 28.5 (CH2). Anal. Calcd for
C17H30N5O10S3F9Os: C, 22.15; H, 3.28; N, 7.60. Found: C, 21.76;
H, 3.26; N, 7.75.
[Os(NH3)5{2,3-η2-(1-(methoxymethyl)-4-(2′-(2′-carbomethoxy)-
propyl)-1,4-dihydronaphthalene)}](OTf)2 (3a). 1H NMR (300 MHz,
acetone-d6): δ 7.24 (d, J ) 6.9 Hz, 1H), 7.20-7.11 (m, 3H), 4.57 (br
s, 3H), 3.95 (d, J ) 9.0 Hz, 1H), 3.82 (d, J ) 6.9 Hz, 1H), 3.71 (s,
3H), 3.69 (m, 1H), 3.49 (d, J ) 9.0 Hz, 1H), 3.39 (s, 3H), 3.35 (br s,
12H), 3.26-3.15 (m, 2H), 1.29 (s, 3H), 1.17 (s, 3H). 13C NMR (75
MHz, acetone-d6): δ 179.5 (C), 138.7 (C), 135.7 (C), 132.4 (CH), 131.6
(CH), 128.0 (CH), 126.7 (CH), 81.9 (CH2), 58.9 (CH3), 52.6 (CH3),
[Os(NH3)5(2,3,4-η3-{1-tert-butyl-1H-naphthalenium)}](OTf)3 (5).
Complex 1 (358 mg, 0.51 mmol) was dissolved in a solution of tert-

7840 J. Am. Chem. Soc., Vol. 120, No. 31, 1998
Winemiller and Harman
51.7 (CH3), 51.0 (C), 50.7(CH), 48.9 (CH), 43.3 (CH), 27.3 (CH3),
21.7 (CH3). Cyclic voltammetry: Ep,a ) 0.70 V.
h. The solution of 3 was instead transferred to a -40 °C bath where
it was cooled for 25 min, then treated with a -40 °C solution of
dimethyl malonate (175 mg, 1.33 mmol) and DIEA (64 mg, 0.50 mmol)
in 440 mg of CH3CN. This new solution was allowed to react for an
additional 10 min at -40 °C, and then added to 5 mL of H2O at room
temperature. Diethyl ether (5 mL) was then added, and the solution
was started stirring rapidly. To this stirring solution was added HOTf
(52 mg, 0.35 mmol) and AgOTf (148 mg, 0.57 mmol), and vigorous
stirring was continued for 0.5 h, after which the entire solution was
transferred to a pressure tube and heated at 80 °C for another 0.5 h.
After cooling, the solution was extracted with ether, then back extracted
with 10% NaOH. Column chromatography on silica gel (200 mL of
5% ether/petroleum ether, 100 mL of 10% ether/petroleum ether, then
20% ether/petroleum ether until completion) yielded 40 mg of 3b′ (0.13
mmol, 54%). 1H NMR (300 MHz, CDCl3): δ 7.22 (m, 4H), 6.22 (m,
2H), 4.25-4.22 (m, 1H), 3.72 (s, 3H), 3.71-3.53 (m, 4H), 3.65 (s,
3H), 3.36 (s, 3H). 13C NMR (75 MHz, CDCl3): δ 168.6 (C), 168.3
(C), 136.2 (C), 134.9 (C), 129.0 (CH), 128.5 (CH), 127.7 (CH), 127.0
(CH), 126.7 (CH), 126.2 (CH), 77.5 (CH2), 59.3 (CH3), 60.0 (CH),
52.6 (CH3), 52.6 (CH3), 41.1 (CH), 39.5 (CH). Anal. Calcd for
C17H20O5 : C, 67.09; H, 6.62. Found: C, 66.56; H, 6.84.
1-(Methoxymethyl)-4-(2′-(2′-carbomethoxy)propyl)-1,4-dihydro-
naphthalene (3a′). The procedure for 3 was followed starting with
233 mg (0.33 mmol) of complex 1, but the product was not precipitated
at the end of 1 h. The solution of 3 was instead transferred to a -40
°C bath where it was cooled for 25 min, then treated with a -40 °C
solution of methyl trimethylsilyl dimethylketene acetal (292 mg, 1.68
mmol) in 730 mg of CH3CN. This new solution was allowed to react
for an additional 10 min at -40 °C, then added to 5 mL of H2O at
room temperature. Diethyl ether (5 mL) was then added, and the
solution was started stirring rapidly. To this stirring solution was added
AgOTf (211 mg, 0.82 mmol), and vigorous stirring was continued for
0.5 h, after which the entire solution was transferred to a pressure tube
and heated at 80 °C for another 0.5 h. After cooling, the solution was
extracted with ether and column chromatography on silica gel (200
mL of 5% ether/petroleum ether, 100 mL of 10% ether/petroleum ether,
then 20% ether/petroleum ether until completion) yielded 59 mg of
3a′ (0.22 mmol, 65%). 1H NMR (300 MHz, CDCl3): δ 7.29 (dd, J )
7.2, 1.5 Hz, 1H), 7.23-7.1 (m, 2H), 7.04 (d, J ) 7.8 Hz, 1H), 6.14
(dd, J ) 10.35, 4.5 Hz, 1H), 5.85 (dd, J ) 10.35, 4.5 Hz, 1H), 3.95
(m, 1H), 3.75 (s, 3H), 3.69 (m, 3H), 3.41 (s, 3H), 1.11 (s, 3H), 1.07 (s,
3H). 13C NMR (75 MHz, CDCl3): δ 178.1 (C), 136.6 (C), 134.7 (C),
129.3 (CH), 129.1 (CH), 128.7 (CH), 126.3 (CH), 126.1 (CH), 125.8
(CH), 78.6 (CH2), 58.9 (CH3), 51.8 (CH3), 47.2 (C), 46.3 (CH), 40.7
(CH), 23.1 (CH3), 22.6 (CH3). Anal. Calcd for C17H22O3: C, 74.42;
H, 8.08. Found: C, 73.98; H, 8.30.
Benchtop Procedure. The procedure was started with 1.06 g of
[Os(NH3)5(OTf)](OTf)2 dissolved in 3.3 g of degassed DMAc in a 10-
mL round-bottom flask. It is important to eliminate oxygen from the
solvent before addition of the ligand and Mg0. Next 1.96 g of
naphthalene was added and stirring was commenced before the first
1.5 g of Mg0 was added. If the magnesium is not stored under nitrogen,
the magnesium should be activated (I2) prior to use and used
immediately. After 0.5 h, another 1.5 g of Mg0 was added to ensure
completion of the complexation, and stirring was continued for an
additional 0.5 h. At the end of this 1 h, the solution was filtered through
a 125-mL medium frit into a stirring solution of CH2Cl2, and the
resulting precipitate was filtered and washed with more CH2Cl2 followed
by ether to yield 880 mg (1.25 mmol) of naphthalene complex (85%).
The complex was immediately placed into a 25-mL round-bottom flask
under an atmosphere of argon, dissolved in a solution of dimethoxy-
methane (257 mg, 3.38 mmol) in 2.12 g of CH3CN, and treated with
a solution of HOTf (406 mg, 2.71 mmol) in 2.1 g of CH3CN. At the
end of 1 h, the flask was placed into a -40 °C bath where it was cooled
for 25 min, then treated with a -40 °C solution of methyl trimethylsilyl
dimethylketene acetal (1.10 g, 6.31 mmol) in 540 mg of CH3CN. This
new solution was allowed to react for an additional 10 min at -40 °C,
then added to 5 mL of H2O containing HOTf (280 mg, 1.87 mmol) at
room temperature. Diethyl ether (5 mL) was then added, and the
solution was started stirring rapidly. To this stirring solution was added
AgOTf (651 mg, 2.53 mmol), and vigorous stirring was continued for
0.5 h, after which the entire solution was transferred to a pressure tube
and heated at 80 °C for another 0.5 h. After cooling, the solution was
extracted with ether and column chromatography on silica gel (200
mL of 5% ether/petroleum ether, 100 mL of 10% ether/petroleum ether,
then 20% ether/petroleum ether until completion) yielded 171 mg of
3a′ (0.63 mmol, 50%).
[Os(NH3)5{2,3-η2-(1-(methoxymethyl)-4-(1′-propan-2′-one)-1,4-
dihydronaphthalene)}](OTf)2 (3c). 1H NMR (300 MHz, CD3CN):
δ 7.15-7.05 (m, 4H), 3.98 (br s, 3H), 3.71 (dd, J ) 9.0, 5.7 Hz, 1H),
3.63 (dd, J ) 9.0, 5.4 Hz, 1H), 3.57 (d, J ) 9.0 Hz, 1H), 3.49 (d, J )
9.0 Hz, 1H), 3.31 (s, 3H), 3.24-2.97 (m, 4H), 2.81 (br s, 12H), 2.15
(s, 3H). 13C NMR (75 MHz, CD3CN): δ 209.9 (C), 140.0 (C), 137.6
(C), 130.9 (CH), 129.8 (CH), 128.2 (CH), 127.4 (CH), 82.7 (CH2),
59.2 (CH3), 56.9 (CH2), 53.6 (CH), 50.9 (CH), 42.9 (CH), 37.6 (CH),
30.9 (CH3). Cyclic voltammetry: Ep,a ) 0.66 V.
1-(Methoxymethyl)-4-(1′-propan-2′-one)-1,4-dihydronaphtha-
lene (3c′). The procedure for 3 was followed starting with 364 mg
(0.52 mmol) of complex 1 but was not precipitated at the end of 1 h.
The solution of 3 was instead transferred to a -40 °C bath where it
was cooled for 25 min and then treated with a -40 °C solutions of
di-tert-butylpyridine (209 mg, 1.09 mmol) in 820 mg of CH3CN and
siloxypropene (366 mg, 2.81 mmol). This new solution was allowed
to react for an additional 1 h at -40 °C, then added to 5 mL of H2O
at room temperature. Diethyl ether (5 mL) was then added, and the
solution was started stirring rapidly. To this stirring solution was added
AgOTf (350 mg, 1.36 mmol), and vigorous stirring was continued for
0.5 h, after which the entire solution was transferred to a pressure tube
and heated at 80 °C for another 0.5 h. After cooling, the solution was
extracted with ether and column chromatography on silica gel
(petroleum ether until the di-tert-butylpyridine was gone, then 200 mL
of 5% ether/petroleum ether, 100 mL of 10% ether/petroleum ether,
and 20% ether/petroleum ether until completion) yielded 83 mg of 3c′
(0.36 mmol, 69%). 1H NMR (300 MHz, CDCl3): δ 7.20 (m, 4H),
6.09 (dd, J ) 10.2, 4.8, 1H), 5.98 (dd, J ) 10.2, 4.2, 1H), 3.96 (m,
1H), 3.59 (m, 1H), 3.56 (dd, J ) 8.4, 5.4, 1H), 3.46 (dd, J ) 8.4, 6.6,
1H), 3.35 (s, 3H), 2.83 (dd, J ) 16.95, 5.1, 1H), 2.69 (dd, J ) 16.95,
9.0, 1H), 2.13 (s, 3H). 13C NMR (75 MHz, CDCl3): δ 207.1 (C),
138.4 (C), 135.7 (C), 129.8 (CH), 128.6 (CH), 127.8 (CH), 127.2 (CH),
126.6 (CH), 126.1 (CH), 78.9 (CH2), 59.0 (CH3), 54.3 (CH2), 40.6
(CH), 35.3 (CH), 30.7 (CH3). Anal.Calcd for C15H18O2 : C, 78.23; H,
7.88. Found: C, 77.88; H, 8.29.
Acknowledgment. Acknowledgment is made to the Camille
and Henry Dreyfus Foundation, National Science Foundation
(CHE-9212008 and NSF Young Investigator program), and A.
P. Sloan Foundation for their generous support of this work.
Thanks also goes to Ben Brooks for his help in obtaining
elemental analyses of these sensitive compounds.
[Os(NH3)5{2,3-η2-(1-(methoxymethyl)-4-(2′-dimethyl malonate)-
1,4-dihydronaphthalene)}](OTf)2 (3b). 1H NMR (300 MHz, acetone-
d6): δ 7.18-7.08 (m, 3H), 6.98 (d, J ) 6.9 Hz, 1H), 4.59 (br s, 3H),
4.10 (d, J ) 9.6 Hz, 1H), 3.78 (d, J ) 9.6 Hz, 1H), 3.73 (s, 3H), 3.47
(s, 3H), 3.36 (br s, 12H), 3.31 (s, 3H), 3.29-3.22 (m, 4H), 2.86 (d, J
) 5.7 Hz, 1H). 13C NMR (75 MHz, acetone-d6): δ 179.5 (C), 138.7
(C), 135.8 (C), 132.4 (CH), 131.6 (CH), 127.9 CH), 126.7 (CH), 81.9
(CH2), 58.9 (CH3), 52.6 (CH3), 51.7 (CH), 51.0 (C), 50.7 (CH), 48.9
(CH), 43.3 (CH), 27.3 (CH3), 21.7 (CH3). Cyclic voltammetry: Ep,a
) 0.73 V.
Supporting Information Available: Text giving experi-
mental procedures and characterizations for all compounds
described in this account (7 pages, print/PDF). See any current
masthead page for ordering information and Web access
instructions.
1-(Methoxymethyl)-4-(2′-dimethyl malonate)-1,4-dihydronaph-
thalene (3b′). The procedure for 3 was followed starting with 171
mg (0.24 mmol) of complex 1 but was not precipitated at the end of 1
JA980624T