Enantioselective catalysis using planar chiral η6-arene chromium complexes: 1,2-Diols as cycloaddition catalysts

Article abstract of DOI:10.1016/S0957-4166(00)00411-0

A highly selective Diels-Alder catalyst has been prepared from a commercially available tetrahydronaphthalene diol. Stereocontrol is greatly enhanced by introduction of a planar chiral arene chromium tricarbonyl group, achieved by face selective complexat

Full text of DOI:10.1016/S0957-4166(00)00411-0

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 11 (2000) 4303–4320
6
Enantioselective catalysis using planar chiral h -arene
chromium complexes: 1,2-diols as cycloaddition catalysts
a,
a
b
Graham B. Jones, * Mustafa Guzel and Steven B. Heaton
a
Bioorganic and Medicinal Chemistry Laboratories, Department of Chemistry, Northeastern University, Boston,
MA 02115, USA
b
Process Technology Department, Roche Carolina Inc., 6173 East Old Marion Highway, Florence, SC 29502, USA
Received 29 August 2000; accepted 18 September 2000
Abstract
A highly selective Diels–Alder catalyst has been prepared from a commercially available tetra-
hydronaphthalene diol. Stereocontrol is greatly enhanced by introduction of a planar chiral arene
chromium tricarbonyl group, achieved by face selective complexation. The factors influencing stereoselec-
tivity with the catalyst have been investigated and delineated. Under optimal conditions, the catalyst gives
>95% e.e. and 98:2 exo:endo ratio in the cycloaddition of methacrolein and cyclopentadiene. © 2000
Elsevier Science Ltd. All rights reserved.
1
. Introduction
Following on from their extensive application in asymmetric synthesis, the use of arene
1
2
chromium carbonyl complexes as asymmetric catalysts is now becoming commonplace. We and
others have demonstrated that the tricarbonyl chromium group is a powerful stereodirective
element in both chiral catalysts and auxiliaries, and that electronic control is afforded by
mixed-ligand arene chromium carbonyl systems, ranging from inductive effects on ring
substituents to modulation of arene facial p-donor ability. Combined, these effects can serve as
powerful control elements in catalyst design, either by amplifying asymmetric induction of
existing arene-based catalysts, or by introduction of planar chirality (Fig. 1).
3,4
5
6
*
Corresponding author. Fax: 617-373-8795; e-mail: grjones@lynx.neu.edu
0
957-4166/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(00)00411-0

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G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
Figure 1.
6
Based on encouraging results with auxiliaries in cycloaddition reactions, we sought to
develop an efficient and readily available intermolecular Diels–Alder catalyst incorporating the
above design features. Specifically, we sought a commercially available building block which
offered the potential for formation of a five-membered metallocycle, and could be directly
converted to a planar chiral arene complex.
To provide proof of principle, arene diol complexes were selected since (i) endo complexation
of the metal carbonyl group is precedented (Scheme 1), (ii) asymmetric hydroxylation methods
provide enantiospecific routes to the ligands 2, allowing (iii) access from a wide variety of readily
available vinyl arene building blocks.
Scheme 1. Ligand design strategy
2
. Results and discussion
In order to highlight the role of the metal carbonyl tripod most effectively, our initial
vinylarenes were m-substituted styrenes, since a corresponding o-substituent might be expected
to impact on our ability to fine-tune stereocontrol. Accordingly, m-anisaldehyde was subjected
7
to olefination followed by Sharpless dihydroxylation to give (S)-diol 3 in >99% e.e. (Scheme 2).

G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
4305
Complexation at this point using conventional conditions gave a moderate yield of a 9:1 mixture
of diastereomers 4 and 5, which were separable using chromatographic methods. Protection of
the hydroxyl functions in the form of ketal 6 followed by complexation gave a higher yield of
complex 7, but in a ratio of 5:1 in favor of the (S,1R) complex, confirmed on deprotection to
give 4. The identity of facial diastereomers 4/5 was established via oxidative cleavage to give the
8
known aldehydes 8.
Scheme 2. Preparation and stereochemical assignment of m-methoxystyrene derived ligands
The diols were then exposed to a variety of Lewis acids, and the corresponding metallocycles/
chelates examined in the catalytic enantioselective cycloaddition of 2-methacrolein with
cyclopentadiene, using catalysts derived from 3 as controls. Though an exo-preference was
observed with every Lewis acid combination examined, the (R)-enantiomeric cycloaddition
product 13 was favored with both the boron and titanium metallocycles and the (S)-enantiomer
1
4 predominated with the aluminum metallocycles (Scheme 3, Table 1).
Scheme 3. Metallodioxolane catalyzed [4+2] cycloadditions

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G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
Table 1
a
Enantioselective cycloaddition of 2-methacrolein using arene diol catalysts
b
c
d
Entry
Diol
Mol%
LA
Prod. (%)
Exo:endo
% e.e.
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
5
4
4
4
4
4
3
5
4
4
3
5
4
4
3
4
20
20
20
20
20
20
20
20
20
20
80
20
20
20
100
20
20
20
20
20
20
20
BH Br
13 (99)
13 (83)
13 (91)
13 (95)
13 (95)
13 (87)
13 (75)
14 (98)
14 (82)
14 (83)
14 (82)
14 (67)
14 (92)
14 (99)
14 (83)
13 (91)
13 (87)
14 (97)
14 (99)
14 (89)
14 (92)
14 (84)
92:8
95:5
96:4
90:10
81:9
86:14
99:1
66:34
99:1
98:2
99:1
85:15
96:4
95:5
96:4
64:36
73:27
98:2
95:5
98:2
97:3
99:1
19
20
39
0
44
43
0
21
31
41
41
29
53
61
62
28
46
20
36
51
37
52
2
BH Br
2
BH Br
2
BCl3
BHCl2
BHBr2
e
BF OEt2
3
Et AlCl
2
Et AlCl
2
1
1
1
1
1
1
1
1
1
1
2
2
2
Et AlCl
2
Et AlCl
2
EtAlCl2
EtAlCl2
EtAlCl2
EtAlCl2
TiCl OiPr2
2
TiCl OiPr2
2
12
11a
11a
11b
11b
Et AlCl
2
Et AlCl
2
EtAlCl2
Et AlCl
2
EtAlCl2
a
b
c
All reactions employed 0.5 mmol substrate in CH Cl (−78°C/24 h).
2
2
Isolated yields following SGC.
1
Determined by H NMR of crude isolates.
d
e
Determined by chiral shift analysis using Eu(hfc)3.
Conducted in THF.
A key feature of these catalysts is the geometric flexibility at the Lewis acidic metal center,
designed to accommodate a variety of substrate dienophiles. Boronates were in general less
selective than the aluminates, and within this class, aluminates capable of forming bona fide
metallocycles (entries 8–11) less discriminating than the dihaloaluminates (entries 12–15). As
noted above, the coordinative geometry of the metal center itself also has a profound effect on
product enantiomer distribution. Though selectivity is modest (<65% e.e.), catalysts derived
from 4 are routinely superior to 5, which are in turn superior to uncomplexed analogs 3.
However, since the same enantiomeric product predominates using either 4 or 5 this suggests
that the entire arene metalꢀcarbonyl appendage is functioning as a stand alone stereodirective
element, a function of its planar chirality. In an effort to amplify the effects, mixed ligand
derivatives of diols 4 and 5 were prepared (Scheme 2). Accordingly, silylation of 3 followed by
complexation gave a mixture of diastereomers 9 and 10, which were separated and subjected to
photolytic ligand exchange, resulting in ligands 11 and 12 following deprotection. Under
analogous reaction conditions, inferior enantiocontrol was afforded by both of these systems,
complicated by the fact that partial decomplexation ensued (up to 20%) during the reaction
(
Table 1, entries 18–22). In an effort to improve the system, complexes derived from (S)-1-naph-
thyl diol 15 and 2-naphthyl diol 16 were prepared. Both systems were inferior to ligand 4

G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
4307
(
maximum e.e.<40% with Et AlCl) and additionally were far less stable, resulting in substantial
2
decomplexation under typical cycloaddition conditions. To uncouple the contribution of the
planar chirality from 4, complex 17 was prepared from (S)-styrene diol. The maximum e.e.
attainable with catalysts derived from 17 was 15%, confirming the dominant role that the planar
chiral template imparts. Based on these findings, the logical way forward was to exploit the
influence of the metal carbonyl complex in a more rigidified catalyst framework, and thus
redirect efforts towards bicyclic diols.
Accordingly, the indane diol ligand 18 was prepared, and catalysts derived from 18 and 19
were examined (Scheme 4). Unfortunately, despite numerous refinements, the direct route to 18
7
(
asymmetric dihydroxylation of indene) provided diol ligands in <50% e.e. Nevertheless,
preliminary analysis suggests that appreciable selectivity is attainable from this ligand family, as
a boron metallocycle derived from 19 gave a product e.e. in excess of 60% (Table 2, entry 7).
Should efficient chemical or enzymatic approaches to 18 become available, we believe this could
provide access to an extremely selective catalyst family, in both the complexed and uncomplexed
series.
Scheme 4. Preparation of indene analogs
Since one of our objectives was to utilize a diol ligand of high enantiomeric purity (Scheme
1
), we turned our attention to the corresponding tetrahydronaphthalene diols. Indeed, though
asymmetric dihydroxylation of 1,2-dihydronaphthalene can be performed, the product, (1R,2S)-
,2,3,4-tetrahydro-1,2-naphthalenediol 20, is commercially available in enantiomerically pure
1
6
form. Accordingly, this diol was converted directly to the h -arene complex by thermolysis with
hexacarbonylchromium, giving the desired product in high yield (Scheme 5). As is typical in
such reactions, the endo complex predominates, giving a 8:1 mixture of 21:22 when a THF/n-
butyl ether solvent mixture is used for complexation. Alternatively, protection of the diol then
complexation gave a mixture of 23 and its exo isomer, readily separable using SGC. Stereochem-

4308
G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
Table 2
a
Enantioselective cycloaddition of 2-methacrolein using bicyclic diol catalysts
b
c
d
Entry
Ligand
Mol%
Lewis acid
Temp. (°C)
% 13
Exo:endo
% e.e.
e
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
18
19
20
20
20
20
20
20
20
20
20
20
20
20
20
20
10
10
100
20
20
20
20
20
20
20
20
20
20
20
20
20
Et AlCl
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−95
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
62
70
89
66
81
89
58
84
72
84
90
89
83
79
82
80
87
81
85
77
32
99
88
99
99
59
86
92
82
89
88:12
92:8
95:5
97:3
97:3
95:5
99:1
93:7
88:12
97:3
89:11
95:5
96:4
83:17
98:2
89:11
98:2
98:2
93:7
93:7
80:20
91:9
89:11
95:5
97:3
72:28
95:5
95:5
86:14
92:8
29
18
14
22
28
13
62
23
19
48
54
79
90
25
84
72
91
2
e
Et AlCl
2
f
19
Et AlCl
2
e
18
19
18
19
20
20
20
20
21
21
22
21
21
21
21
EtAlCl2
EtAlCl2
e
e
BH Br·Me S
2
2
e
BH Br·Me S
2 2
BH Br·Me S
2 2
BHBr ·Me S
2
2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
EtAlCl2
Et AlCl
2
EtAlCl2
Et AlCl
2
Et AlCl
2
Et AlCl
2
EtAlCl2
Et AlCl
2
g
Et AlCl
\95
2
24a
24a
24b
24c
24d
24e
24f
24g
24h
24h
25
Et AlCl
66
49
56
55
62
60
78
78
86
71
29
43
2
EtAlCl2
Et AlCl
2
Et AlCl
2
Et AlCl
2
Et AlCl
2
Et AlCl
2
Et AlCl
2
Et AlCl
2
EtAlCl2
Et AlCl
2
26
Et AlCl
2
a
Ligand and Lewis acid equilibrated at 25°C/3 h then cooled to −78°C for addition of substrates. All reactions
employed 0.5 mmol substrate in CH Cl .
2
2
b
c
d
e
f
Isolated yields following SGC.
1
Determined by H NMR of crude isolates.
Determined by chiral shift analysis using Eu(hfc)3.
E.e. of diol ligand was 47%.
E.e. of diol ligand was 21%.
Up to 97% e.e. obtained.
g
ical assignment of 23 was confirmed by X-ray crystallography, and this key intermediate allowed
ligand substitution to be performed, giving a range of mixed ligand complexes 24 on deprotec-
9
tion. The ligands were then exposed to a variety of Lewis acids, and the resulting metallocycles/
chelates examined in the catalytic enantioselective cycloaddition of 2-methacrolein with
cyclopentadiene, using catalysts derived from 20 as controls (Scheme 3). In all cases examined
(
as with ligands 18 and 19), exo-(R)-cycloadduct 13 was formed in preference to (S)-14. The
uncomplexed diol 20 alone offered moderate to good enantioselectivity, performing better with

G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
4309
Scheme 5. Preparation of mixed ligand naphthalene diol derived ligands
aluminum derived metallocycles rather than the boronates (Table 2, entries 8–11). A substantial
ꢀ40%) enhancement was obtained using its corresponding endo arene complex 21, resulting in
90% e.e., whereas catalysts derived from 22 proved inferior to the uncomplexed system 20
entries 12–14). While a slight decrease in selectivity was observed using 10 mol% catalyst, no
(
>
(
substantial increases were observed using stoichiometric amounts; however, at lower tempera-
tures enantioselectivity increased to >95% (entries 15–18), rendering the system highly competi-
1
0
tive with existing catalysts. The diol ligand 21 could be recovered intact following hydrolytic
workup, making this an attractive candidate for use in asymmetric syntheses. We anticipated
that modification of the steric parameters around the ligand tripod of 21 would provide further
increases in selectivity. Surveying a panel of eight different mixed-ligand derivatives 24a–h failed,
however, to yield any improvement over the ‘parent’ tricarbonyl chromium complex (entries
1
9–28). The reasons for this could be several fold, including competing interactions of the Lewis
acidic aluminum center with the phosphine and phosphite ligands. However, as was the case
with mixed ligand systems 11 and 12, in situ decomplexation proved problematic and, given the
inferior performance of ligand 20, the figures reported presumably reflect this process. The
superior performance of catalysts derived from diethyl aluminum chloride suggests the involve-
ment of a five-membered chloroaluminum metallocyclic Lewis acid. Indeed, in all the reactions
studied, the aluminum species and diol were pre-equilibrated for 3 h before addition of the
substrates. Reduction of this time led to a precipitous drop in product e.e., since free Lewis acid is
available to catalyze the reaction. To underscore the need for a cyclic Lewis acid structure,
analogous catalysts derived from (S)-tetralol 25 and 26 were prepared and, as expected, they
offered greatly inferior stereocontrol (Table 2, entries 29 and 30).

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G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
Our working hypothesis for the transition state assembly involves preferential substrate (enal)
6
coordination exo to the metallocycle, influenced heavily by the h -arene complex. We speculate
that additional interactions of the aluminum species with the metal carbonyl tripod may explain
11
the anomalously high levels of asymmetric induction attained using 21. Potential transition
state models include Fig. 2, where enal coordination directs attack of the diene anti to the metal
carbonyl group, to give the observed exo-(R) product under either scenario. Such a model
predicts the diene approach vector to be predetermined (N.B. catalyst aging time is critical), but
relies on the presence of the a methyl group to establish the indicated s-trans enal geometry. To
underline this requirement, cycloaddition to acrolein was conducted using ligand 21 (Scheme 6),
and resulted in formation of endo-(R) product 27 with cyclopentadiene, and (R)-cycloadduct 28
with dimethylbutadiene. The apparent reversal in facial selectivity 27 presumably reflects s-cis
10
enal coordination, as has been observed with related catalysts. Significantly, the present study
confirms that the level of facial and enantiocontrol afforded by catalysts derived from 21 is
comparable or superior to existing systems, with the added advantage that ligand 20 is
commercially available. Thus, while the full utility of these systems in asymmetric synthesis
remains to be seen, they constitute a promising and novel addition to the arsenal of available
asymmetric Diels–Alder catalysts.
Figure 2. Proposed transition state models for addition to methacrolein with ligand 21
Scheme 6. Enantioselective cycloadditions to acrolein with catalyst derived from 21
3
. Conclusion
A new class of planar chiral asymmetric Diels–Alder catalyst has been developed, and the
factors which contribute to asymmetric induction have been probed. The optimal ligand 21 can
be prepared in one step from a commercially available diol and is highly selective, making the
catalyst a viable and readily available entity. Based on the general design criteria outlined herein
(
Scheme 1), we anticipate that many variants may be possible, including application in the
asymmetric catalysis of other carbonꢀcarbon bond forming reactions. In addition, we believe

G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
4311
that the synergy afforded by combining a planar chiral template with an enantiopure diol will
find application in the design of other catalysts, including ferrocenes and polymer supported
variants.
4
. Experimental
General methods for synthesis, and the preparation and handling of chromium complexes
1
2
6
a
have been published. Ether, THF and n-butyl ether were distilled from sodium benzophenone
ketyl. Hexanes and benzene were distilled from calcium hydride. Dichloromethane was distilled
from P O before use. DMF was dried stirring with BaO for 12 h at room temperature, followed
2
5
by distillation from alumina at reduced pressure. Solvents used for complexations were
deoxygenated by three cycles of freezing under vacuum, purging with nitrogen gas and thawing.
Acroleins were distilled from calcium hydride immediately prior to use. Hexacarbonyl chromium
was purchased from Strem Chemicals Inc. and used as supplied. All other chemicals were
purchased from Aldrich and used as supplied.
4
.1. (S)-1-(m-Methoxy phenyl)ethane-1,2-diol 3
AD-mix-a (15.65 g) was added to a solution of t-BuOH (160 ml) and H O (160 ml) and the
2
resulting mixture stirred at room temperature for 30 min. On cooling to 0°C, m-methoxystyrene
(
(
1.50 g, 11.18 mmol) was added, and the mixture stirred vigorously at 0°C for 9 h. Solid Na SO3
16.77 g, 13 mmol) was added, and the mixture allowed to warm to ambient temperature, stirred
2
for 1 h, then the solution was washed with EtOAc (2×150 ml). The organic extracts were
combined, dried (MgSO ), filtered, and condensed in vacuo to give the title compound (1.87 g,
4
1
9
9%) as a colorless oil. H NMR (300 MHz, CDCl ) l 7.14–7.09 (t, J=7.8 Hz, 1H), 6.84–6.80
3
(
dd, J=11.7 Hz, 2.4 Hz, 2H), 6.70–6.67 (dd, J=8.1 Hz, 2.4 Hz, 1H), 4.67–4.63 (dd, J=8.1 Hz,
3
2
1
.3 Hz, 1H), 4.25 (br, 2H), 3.62–3.58 (dd, J=14.7 Hz, 3.3 Hz, 1H), 3.52–3.46 (dd, J=8.4 Hz,
1
3
.7 Hz, 1H) and 3.69 (s, 3H); C NMR (75 MHz, CDCl ) l 159.3, 142.6, 128.9, 118.1, 112.7,
3
−
1
11.3, 73.9, 67.8 and 54.8; IR (neat) 3412.8 (br), 3097.9, 3046.8, 1812.8, 1480.9 and 1029.8 cm ;
+
MS (m/e) 168 (M , 100%); [h] =+71.8 (c=0.5, CHCl ); HPLC (Daicel OD, 90:10 hexanes:IPA
as eluent, 1 ml min ) t 11.90 min minor (R), t 13.23 min major (S), (e.e.>99.5%); C H O
D
3
−
1
R
R
9
12
3
requires: C, 64.27; H, 7.19; found: C, 64.41; H, 7.37.
.2. (1S)-(1-Naphthyl)ethane-1,2-diol
Under similar conditions, 1-vinylnaphthalene (3.00 g, 19.51 mmol) gave the title compound
4
1
(
3.22 g, 88%) as a white solid, mp 118–119°C; H NMR (300 MHz, CDCl ) l 8.05–8.03 (d,
3
J=6.9 Hz, 1H), 7.88–7.81 (dd, J=9 Hz, 2.7 Hz, 2H), 7.69 (d, J=7.2 Hz, 1H), 7.50–7.46 (dd,
J=9.9 Hz, 2.4 Hz, 3H), 5.63 (d, J=5.1 Hz, 1H), 3.99–3.96 (d, J=9 Hz, 1H), 3.81–3.74 (dd,
13
J=11.4 Hz, 3 Hz, 1H), 2.89 (br, 1H) and 2.46 (br, 1H); C NMR (75 MHz, CDCl ) l 133.2,
3
1
3
1
6
29.6, 129.0, 128.3, 127.4, 126.2, 125.4, 121.3, 112.4, 109.6, 91.3 and 74.6; IR (neat) 3251.1 (br),
097.9, 3038.3, 2323.4, 1966.0, 1829.8, 1489.4, 1029.8, 783.0 and 672.3; MS (m/e) 188 (M ,
+
00%); [h] =+45.6 (c=0.5, CHCl ); C H O requires: C, 76.58; H, 6.42; found: C, 76.64; H,
D
3
12 12
2
.51.

4312
G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
4
.3. (1S)-(2-Naphthyl)ethane-1,2-diol
Under similar conditions, 2-naphthyl-ethylene (2.00 g, 12.97 mmol) gave the title compound
1
(
1.55 g, 64%) as a white solid, mp 113–115°C; H NMR (300 MHz, CDCl ) l 7.86–7.83 (d,
3
J=6.9 Hz, 4H), 7.48 (t, J=7.8 Hz, 3H), 5.01 (t, J=6 Hz, 1H), 3.84–3.76 (dd, J=12.4 Hz, 1.2
13
Hz, 2H), 2.68 (br, 1H) and 2.12 (br, 1H); C NMR (75 MHz, CDCl ) l 137.2, 134.7, 131.9,
3
1
1
29.7, 128.3, 127.5, 127.1, 126.5, 126.0, 125.2, 47.9 and 35.9; IR (neat) 3208.5 (br), 1523.4,
+
072.3, 1021.3 and 774.5; MS (m/e) 188 (M , 100%); [h]=+8.3 (c=0.5, CH OH); C H O
3
12 12
2
requires: C, 76.58; H, 6.42; found: C, 76.73; H, 6.59.
4
.4. (1S)-1-(Phenyl)ethane-1,2-diol
Under similar conditions, styrene (1.7 ml, 15.0 mmol) gave the title compound (1.9 g, 92%) as
7
b
1
a white solid, mp 87–89°C; Lit. 86–87°C; H NMR (300 MHz, CDCl ) l 7.30 (m, 5H), 4.75
3
13
(
d, J=6 Hz, 1H), 4.43 (s, 1H), 4.09 (m, 1H), 3.64–3.59 (br, 2H); C NMR (75 MHz, CDCl3)
l 140.7, 128.7, 128.1, 126.3, 126.1, 74.9 and 68.2; IR (neat) 3390 (br), 3126, 3034, 1490 and 1047
−
1
+
cm ; MS (m/e) 138 (M , 100%); [h] =+61.5 (c=0.5, CHCl ).
D
3
4
.5. (1R,2S)-1,2-Indane-1,2-diol 18
Under similar conditions, indene (0.88 ml, 7.5 mmol) gave (1R,2S)-1,2-indanediol as a white
1
3
13 1
solid (0.92 g, 82%), mp 98–99°C (Lit. 99–100°C) identical to authentic material. H NMR
(
300 MHz, CDCl ) l 7.37 (d, J=6.3 Hz, 1H), 7.25–7.22 (m, 3H), 4.85 (d, J=4.5 Hz, 1H), 4.34
3
(
t, J=4.2 Hz, 1H), 3.37 (br, 2H), 3.06–2.99 (dd, J=16.2 Hz, 5.7 Hz, 1H), 2.90–2.85 (dd, J=16.5
1
3
Hz, 0.9 Hz, 1H); C NMR (75 MHz, CDCl ) l 141.8, 140.1, 128.6, 126.9, 125.2, 124.9, 75.8,
3
7
3.3 and 38.2; [h] =+24.8 (c=0.5, CHCl ); HPLC (Daicel OJ, 95:5 hexanes:IPA as eluent, 1 ml
D
3
−
1
min ) t 18.13 min major (1R,2S), t 22.92 min minor (1S,2R), (e.e.=47.0%).
R
R
4
.6. (S)-1,2-Bis(trimethylsilyloxy)-1-(m-methoxyphenyl)ethane
To a solution of 3 (0.47 g, 2.78 mmol) and imidazole (1.89 g, 27.8 mmol) in DMF (2 ml) was
added TMSCl (1.41 ml, 11.13 mmol), and the solution stirred at rt for 48 h. The mixture was
poured over iced HCl (1%, 50 ml), extracted with EtOAc (2×50 ml) then the organic extracts
were immediately washed with iced NaHCO solution (sat. 1×50 ml) and brine (1×50 ml). The
3
organic extracts were combined and condensed in vacuo, and the residual oil was purified by
SGC (95:5 through 70:30 hexane:ether) to give the title compound (0.80 g, 92%) as a colorless
1
oil. H NMR (300 MHz, CDCl ) l 7.23 (t, J=7.8 Hz, 1H), 6.97–6.94 (d, J=2.1 Hz, 1H), 6.94
3
(
m, 1H), 6.82–6.79 (dd, J=7.5 Hz, 1.8 Hz, 1H), 4.74 (t, J=5.7 Hz, 1H), 3.86 (s, 3H), 3.65 (d,
13
J=6 Hz, 2H) and 0.14 (s, 9H), 0.11 (s, 9H); C NMR (75 MHz, CDCl ) l 159.4, 143.8, 128.8,
3
1
18.6, 112.6, 111.7, 75.7, 69.0, 54.8, 0.07 and −0.6; [h] =+47.1 (c=0.5, CHCl ); C H O Si
D
3
15 28
3
requires: C, 57.64; H, 9.03; found: C, 57.91; H, 9.34.
4
.7. (1R,2S)-1,2-Bis(trimethylsilyloxy)-1,2,3,4-tetrahydronaphthalene
Under similar conditions 20 (1.64 g, 10 mmol) gave the title compound (3.16 g, 98%) as a
1
colorless oil; H NMR (300 MHz, CDCl ) l 7.27 (dd, J=6.9 Hz, 3.3 Hz, 1H), 7.22 (m, 2H),
3

G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
4313
7
2
.13–7.11 (dd, J=7.2 Hz, 3.6 Hz, 1H), 4.68 (d, J=2.7 Hz, 1H), 4.01–3.96 (d, J=7.2 Hz, 1H),
.99 (t, J=4.8 Hz, 1H), 2.84–2.81 (m, 1H), 2.24 (m, 1H), 1.76 (m, 1H), 0.24 (s, 9 H) and 0.19
1
3
(
s, 9H); C NMR (75 MHz, CDCl ) l 138.0, 135.9, 129.4, 128.5, 127.4, 125.8, 72.3, 71.2, 27.5,
3
+
2
6.2, 0.84 and 0.27; MS (m/e) 308 (M , 23.6%), 310 (M+2, 89.0%): [h] =−33.7 (c=0.7, CHCl );
D
3
C H O Si requires: C, 62.28; H, 9.14; found: C, 62.49; H, 9.27.
1
6
28
2
4
.8. (1R)-1-(m-Methoxyphenyl)ethane-1,2-diol chromium(0) tricarbonyl 4 and 5
A mixture of 3 (0.49 g, 2.91 mmol) and chromium hexacarbonyl (1.28 g, 5.83 mmol) was
6a
subjected to standard complexation conditions in nBu O:THF (6:1, 70 ml) for 16 h. On cooling,
2
the mixture was filtered and the solution condensed in vacuo to give the corresponding complexes
(
0.45 g), isolated as a 9:1 mixture of diastereomers. The mixture was purified by SGC (60:40
through 10:90, hexanes:ethyl acetate) to give 4 (0.41 g, 47%) and 5 (0.04 g, 5%), both isolated
as yellow oils.
1
Complex 4: H NMR (300 MHz, CDCl ) l 5.79 (d, J=10.6 Hz, 1H), 5.42 (m, 1H), 5.11–5.06
3
13
(
m, 3H), 4.81 (m, 1H), 4.58 (m, 1H), 3.72 (s, 3H) and 2.92 (br, 2H); C NMR (75 MHz, CDCl )
3
l 233.2, 113.8, 94.8, 83.9, 83.0, 72.8, 67.8 and 55.7; IR (neat) 3438.3 (br), 3097.9, 3038.3, 2340.4,
−
1
+
1
983.0, 1897.9, 1812.8, 1480.9 and 1038.3 cm ; MS (m/e) 304 (M , 28.5%); [h] =+142.9 (c=0.5,
D
CHCl ); C H CrO requires: C, 47.38; H, 3.97; found: C, 47.61; H, 4.25.
3
12 22
6
1
Complex 5: H NMR (300 MHz, CDCl ) l 5.61–5.58 (d, J=7.2 Hz, 1H), 5.42 (m, 1H), 5.11
3
13
(
m, 3H), 4.80 (m, 1H), 4.55 (m, 1H), 3.80 (br, 2H) and 3.70 (s, 3H); C NMR (75 MHz, CDCl )
3
l 233.4, 113.9, 95.0, 84.0, 83.2, 72.5, 67.9 and 55.7; IR (neat) 3387.2 (br), 2944.7, 1966.0, 1872.3,
−
1
+
1
548.9, 1472.3, 1276.6 and 1038.3 cm ; MS (m/e) 304 (M , 23.7%); [h] =+31.9 (c=0.5, CHCl ).
D
3
4
.9. (1R)-1,2-Bis(trimethylsilyloxy)-1-(m-methoxyphenyl)ethane chromium(0) tricarbonyl 9 and
1
0
Under similar conditions (S)-1,2-bis(trimethylsilyloxy)-1-(m-methoxyphenyl)ethane (0.31 g,
.00 mmol) and chromium hexacarbonyl (0.55 g, 2.50 mmol) gave 9/10 (0.63 g), isolated as a 1:1
1
mixture of diastereomers. The mixture was purified by SGC (99:1 through 8:2 hexanes:ethyl
acetate) to give 9 (0.32 g, 35%) and 10 (0.32 g, 35%), both isolated as yellow oils.
1
Complex 9 (hR)-diastereomer: H NMR (300 MHz, CDCl ) l 5.52 (m, 2H), 5.20–4.93 (m,
3
13
3
H), 4.53 (d, J=6 Hz, 1H), 3.71 (s, 3H), 3.54 (m, 1H), 0.23 (s, 9H) and 0.09 (s, 9H); C NMR
(
75 MHz, CDCl ) l 233.4, 115.0, 112.6, 93.4, 85.0, 84.1, 78.8, 73.2, 68.7, 55.5, 0.45 and −0.54;
3
IR (neat) 3659.6 (br), 3089.3, 3038.4, 1966.0, 1897.9, 1821.3, 1489.4, 1251.1, 1038.3, 851.1 and
−
1
+
6
89.4 cm ; MS (m/e) 448 (M , 46.5%); [h] =+98.5 (c=0.5, CHCl ); C H CrO Si requires: C,
D
3
18 28
6
2
4
8.19; H, 6.29; found: C, 48.37; H, 6.51.
Complex 10 (hS)-diastereomer: H NMR (300 MHz, CDCl ) l 5.48 (m, 1H), 5.15–4.89 (m,
1
3
13
3
H), 4.62 (m, 1H), 3.69 (s, 3H), 3.47 (m, 1H), 3.40 (s, 1H), 0.24 (s, 9H) and 0.07 (s, 9H);
C
NMR (75 MHz, CDCl ) l 233.3, 113.7, 112.8, 93.4, 84.8, 84.2, 78.7, 72.9, 68.2, 55.6, 0.37 and
3
0
1
.05; IR (neat) 3472.3 (br), 3089.4, 3038.3, 2323.4, 1974.5, 1897.9, 1821.3, 1480.9.4, 1123.4,
−
1
038.3 and 680.9 cm ; [h] =+60.9 (c=0.5, CHCl ).
D
3
4
.10. (1R)-(1-Naphthyl)ethane-1,2 diol chromium(0) tricarbonyl 15
Under similar conditions, (1S)-(1-naphthyl)ethane-1,2-diol (2.05 g, 12.10 mmol) and
chromium hexacarbonyl (4.00 g, 18.16 mmol) gave the title compound (1.43 g, 40%), isolated as

4314
G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
1
a red solid, mp 62–64°C; H NMR (300 MHz, CDCl ) l 7.51 (m, 1H), 7.37 (m, 2H), 6.14 (d,
3
J=6.9 Hz, 1H), 5.72–5.68 (d, J=7.2 Hz, 2H), 5.52 (m, 1H), 5.32 (m, 1H), 5.21–5.19 (d, J=6 Hz,
1
3
1
H) and 4.00 (s, 1H); C NMR (75 MHz, CDCl ) l 232.4, 131.2, 129.6, 128.8, 128.2, 127.2,
3
9
3.6, 92.0, 91.4, 91.2, 88.0, 71.8 and 69.3; IR (neat) 3676.6, 3097.9, 3046.8, 1974.5, 1906.4,
1
821.3, 1497.9, 1038.3 and 672.3; [h] =+73.6 (c=0.5, CHCl ); C H CrO requires: C, 55.56;
D
3
15 12
5
H, 3.73; found: C, 55.84; H, 3.87.
4
.11. (1R)-(2-Naphthyl)ethane-1,2-diol chromium(0) tricarbonyl 16
Under similar conditions, (1S)-(2-naphthyl)ethane-1,2-diol (1.09 g, 5.77 mmol) was reacted
with chromium hexacarbonyl (2.54 g, 11.55 mmol) to give the title compound (0.37 g, 20%) as
a red solid, which decomposed on standing. Immediate protection of the crude material as the
bis(trimethylsilyl)ether (imidazole, TMSCl) allowed purification and characterization of the
1
resulting red oil; H NMR (300 MHz, CDCl ) l 7.83 (m, 1H), 7.48–7.44 (d, J=6.9 Hz, 2H), 6.11
3
(
m, 1H), 5.50–5.47 (m, 2H), 5.34 (m, 1H), 4.73 (d, J=7.2 Hz, 1H), 3.63–3.54 (d, J=8.1 Hz, 2H),
1
3
0
1
1
6
.28 (s, 9H) and 0.10 (s, 9H); C NMR (75 MHz, CDCl ) l 233.4, 129.4, 129.1, 128.5, 128.2,
3
26.7, 125.4, 112.3, 96.3, 90.8, 88.1, 45.6, 27.3, 0.04 and −0.5; IR (neat) 3106, 3055, 1966, 1821,
−
1
489, 1038 and 681 cm ; [h] =+39.9 (c=0.5, CHCl ); C H CrO Si requires: C, 53.82; H,
D
3
21 28
5
2
.02; found: C, 54.14; H, 6.34.
4
.12. (1R)-1-(Phenyl)ethane-1,2-diol chromium(0) tricarbonyl 17
Under similar conditions, (1S)-1-(phenyl)ethane-1,2-diol (0.69 g, 5.0 mmol) and chromium
hexacarbonyl (2.20 g, 10.0 mmol) gave the title compound (1.21 g, 88%) as a yellow solid (mp
1
9
1
8
3–96°C). H NMR (300 MHz, CDCl ) l 5.46–5.37 (m, 5H), 4.71 (d, J=6.9 Hz, 1H), 4.33 (s,
3
1
3
H), 4.11 (s, 1H) and 3.41–3.32 (br, 2H); C NMR (75 MHz, CDCl ) l 232.8, 109.2, 93.8, 91.2,
8.5, 72.7 and 66.8; IR (neat) 3425 (br), 3134, 3038, 1979, 1893, 1818, 1488 and 1041 cm ; MS
m/e) 274 (M , 33.4%); [h] =+95.4 (c=0.5, CHCl ); C H CrO requires: C, 48.18; H, 3.68;
3
−
1
+
(
D
3
11 10
5
found: C, 48.51; H, 3.88.
4
.13. (4S)-4-(m-Methoxyphenyl)-2,2-dimethyl-1,3-dioxolane 6
,2,-Dimethoxypropane (1.89 ml, 15.39 mmol) was added to a solution of 3 (1.73 g, 10.54
2
mmol) and toluenesulfonic acid (0.20 g, 1.03 mmol) in DMF (50 ml). The solution was stirred
at rt for 24 h, then poured into EtOAc (100 ml), and the organic extracts were washed with HCl
(
1%, 3×50 ml) then condensed in vacuo. The residual oil was purified by SGC (98:2 hex-
1
anes:ether) to give 6 (1.6 g, 75%) as a colorless oil; H NMR (300 MHz, CDCl ) l 7.27–7.24 (t,
3
J=3.6 Hz, 1H), 6.94 (m, 2H), 6.84 (d, J=7.8 Hz, 1H), 5.06 (t, J=6.3 Hz, 1H), 4.32–4.27 (dd,
J=8.4 Hz, 1.8 Hz, 1H), 3.81 (s, 3H), 3.70 (t, J=8.1 Hz, 1H), and 1.55 (s, 3H) and 1.49 (s, 3H);
1
3
C NMR (75 MHz, CDCl ) l 139.7, 137.4, 128.5, 127.8, 127.4, 127.1, 126.5, 125.1, 45.2, 44.8,
3
2
4
7.1 and 22.6; [h] =+47.1 (c=0.5, CHCl ).
D
3
.14. (4R)-4-(m-Methoxyphenyl)-2,2-dimethyl-1,3-dioxolane chromium(0) carbonyl 7
(
4S)-4-(m-Methoxyphenyl)-2,2-dimethyl-1,3-dioxolane (2.84 g, 13.66 mmol) and chromium
hexacarbonyl (6.01 g, 27.32 mmol) were subjected to standard complexation conditions in

G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
4315
nBu O:THF (9:1, 100 ml) for 16 h. On cooling, the mixture was filtered and the solution
2
condensed in vacuo to give a quantitative yield of the corresponding complexes (2.2 g), isolated
as a mixture of diastereomers. The mixture was purified by SGC (98:2 through 7:3 hex-
6
6
anes:ether) to give h S 7 (0.22 g, 4.4%) and h R 7 (1.98 g, 43%) isolated as yellow oils.
1
Complex 7 (hR)-diastereomer: H NMR (300 MHz, CDCl ) l 5.51 (m, 1H), 5.34 (m, 1H),
.12 (m, 2H), 4.84 (m, 1H), 4.37 (m, 1H), 3.89 (d, J=7.4 Hz, 1H), 3.70 (s, 3H), and 1.50 (s, 3H),
.42 (s, 3H); C NMR (75 MHz, CDCl ) l 232.4, 117.8, 112.7, 109.1, 94.6, 93.1, 84.2, 60.9, 56.1,
6.2, 43.9, 26.5 and 23.2; IR (neat) 3446.8 (br), 1974.5, 1880.9, 1651.1, 1548.9, 1463.8, 1259.6,
166.0, 1021.3 and 842.6 cm ; [h] =+19.9 (c=0.5, CHCl ).
Complex 7 (hS)-diastereomer: H NMR (300 MHz, CDCl ) l 5.56 (m, 1H), 5.29 (m, 1H),
.07 (m, 2H), 4.82 (m, 1H), 4.34 (m, 1H), 3.86 (d, J=6 Hz, 1H), 3.71 (s, 3H), and 1.51 (s, 3H)
3
5
1
4
1
1
3
3
−
1
D
3
1
3
5
1
3
and 1.44 (s, 3H); C NMR (75 MHz, CDCl ) l 233.7, 118.0, 113.1, 108.0, 94.7, 92.9, 84.5, 60.6,
3
5
6.0, 46.4, 43.6, 26.9 and 24.3; IR (neat) 3429.8 (br), 2936.2, 2366.0, 1985.5, 1893.5 and 1668.1
−
1
cm ; [h] =+60.7 (c=0.5, CHCl ); C H CrO requires: C, 52.33; H, 4.68; found: C, 52.64; H,
D
3
15 16
6
4
.81.
6
4
.15. (p R,1R)-1-(m-Methoxyphenyl)ethane-1,2-diol chromium(0) triphenylphosphine dicarbonyl
1a
1
Triphenyl phosphine (0.68 g, 2.59 mmol) was added to a solution of 9 (0.12 g, 0.26 mmol) in
freshly distilled benzene (5 ml), in a quartz test tube. The mixture was purged (N /20 min, then
2
Ar/20 min) then placed in a photolysis chamber and irradiated (Hanovia 450 W Hg lamp) for
6
h. Evaporation of the solvent followed by SGC (95:5, hexane:ether) gave the corresponding
1
monotriphenylphosphine complex (0.1 g, 54%) as a yellow oil; H NMR (300 MHz, C D ) l
6
6
7
.15–7.03 (m, 15H), 5.72 (m, 1H), 5.16 (m, 1H), 4.74–4.70 (d, J=8.1 Hz, 2H), 4.49 (m, 1H), 3.84
(
s, 1H), 3.75 (s, 1H), 3.57 (s, 3H), 0.25 (s, 9H) and 0.01 (s, 9H). The crude product (0.03 g, 0.04
mmol) was dissolved in distilled MeOH (2 ml), potassium carbonate (0.5 g, 3.6 mmol) was
added, and the mixture stirred at rt for 6 h. The mixture was filtered through a small plug silica
gel (EtOAc, 50 ml) and the solution condensed in vacuo to give 11a (0.02 g, 100%) as a yellow
1
powder, mp 73–74°C (dec.); H NMR (300 MHz, C D ) l 7.15–7.03 (m, 15H), 5.52 (m, 1H),
6
6
4
1
1
2
.86 (m, 1H), 4.50–4.47 (d, J=6.3 Hz, 1H), 4.27–4.24 (d, J=6.6 Hz, 1H), 4.04 (m, 1H), 3.82 (m,
1
3
H), 3.48 (s, 1H) and 3.15 (s, 3H); C NMR (75 MHz, C D ) l 232.4, 133.3, 133.0, 132.6, 129.4,
6
6
28.7, 127.3, 117.4, 109.1, 93.7, 92.8, 88.1, 81.8, 68.9, 55.3 and 25.3; IR (neat) 3429.8, 2927.7,
−
1
+
366.0, 1889.4, 1838.3, 1736.2, 1438.3 and 1251.1 cm ; MS (m/e) 538 (M , 8.05%); [h] =+39.8
D
(
c=0.5, CH OH).
3
6
4
.16. (p S,1R)-1-(m-Methoxyphenyl)ethane-1,2-diol chromium(0) triphenylphosphine dicarbonyl
1
2
Under identical conditions, 10 (0.23 g, 0.86 mmol) gave the corresponding mono-
1
triphenylphosphine complex (0.03 g, 56%) as a yellow oil; H NMR (300 MHz, C D ) l
6
6
7
.15–7.04 (m, 15H), 5.19 (m, 1H), 4.86 (m, 1H), 4.76 (m, 1H), 4.51 (m, 1H), 4.31–4.27 (d, J=8.1
Hz, 1H), 4.14–4.12 (d, J=6 Hz, 1H), 4.05–4.03 (d, J=6 Hz, 1H), 3.16 (s, 3H), 0.21 (s, 9H) and
6
0
.06 (s, 9H), which following deprotection gave (h S,1R)-1-(m-methoxyphenyl)ethane-1,2-diol
chromium(0) triphenylphosphine dicarbonyl (0.02 g, 92%) as a yellow powder, mp 71–73°C
dec.); H NMR (300 MHz, C D ) l 7.15–7.02 (m, 15H), 5.51 (m, 1H), 4.83 (m, 1H), 4.50–4.48
1
(
6
6

4316
G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
(
(
d, J=6 Hz, 1H), 4.27–4.24 (d, J=7.1 Hz 1H), 4.04 (m, 1H), 3.86 (m, 1H), 3.44 (s, 1H), and 3.17
1
3
s, 3H); C NMR (75 MHz, C D ) l 233.7, 133.1, 133.0, 132.8, 128.7, 128.0, 127.6, 117.1, 108.3,
6
6
9
1
3.7, 91.5, 88.1, 81.4, 69.2, 55.2 and 25.1; IR (neat) 3455.3, 2927.7, 2851.1, 1889.4, 1829.8,
−
1
+
736.2, 1608.5, 1438.3, 1063.8, 748.9 and 706.4 cm ; MS (m/e) 538 (M , 10.76%); [h] =+178.6
D
(
c=0.5, CH OH).
3
6
4
.17. (p R,1R)-1-(m-Methoxyphenyl)ethane-1,2-diol chromium(0) tri(p-tolyl)phosphine
dicarbonyl 11b
Under identical conditions, 9 (0.012 g, 0.04 mmol) with tri(p-toluyl)phosphine (0.12 g, 0.38
mmol) gave the corresponding monotri-p-tolyl phosphine complex, which was subjected to
immediate deprotection to give 11b (0.02 g, 87%) isolated as a yellow powder, mp 66–67°C
1
(
dec.); H NMR (300 MHz, C D ) l 7.40–7.35 (d, J=7.5 Hz, 6H), 6.94 (d, J=7.5 Hz, 6H), 5.48
6
6
(
3
m, 1H), 4.98 (m, 1H), 4.67–4.65 (d, J=6 Hz, 1H), 4.32–4.29 (d, J=7.1 Hz, 1H), 4.21 (m, 1H),
.84 (m, 1H), 3.42 (s, 3H), 3.31 (br, 2H), 3.16 (d, J=8.7 Hz, 1H) and 2.04 (s, 9H); C NMR
13
(
75 MHz, C D ) l 234.7, 144.3, 137.3, 133.9, 132.2, 128.5, 128.1, 113.7, 112.4, 95.5, 92.7, 84.8,
6
6
8
7
4.6, 54.6, 30.8, 26.9 and 20.0; IR (neat) 3455, 2945, 2850, 1890, 1830, 1740, 1608, 1438, 1066,
−
1
+
49 and 706 cm ; MS (m/e) 580 (M , 4%); [h] =+122.5 (c=0.5, CHCl ).
D
3
6
4
.18. (p R)-m-Anisaldehyde chromium(0) tricarbonyl 8
To a vigorously stirred solution of lead tetraacetate (0.25 g, 0.56 mmol) in distilled benzene
10 ml), was added 5 (0.17 g, 0.56 mmol, dissolved in 5 ml of benzene). The mixture was stirred
(
at 25°C for 1 h, then the mixture was filtered through a plug of silica gel (EtOAc, 50 ml).
Following condensation in vacuo, the residual oil was purified by SGC (90:10, hexanes:EtOAc)
1
to give the title compound (0.14 g, 90%) as a red solid (mp 87–88°C); H NMR (300 MHz,
13
CDCl ) l 9.58 (s, 1H), 5.56 (dd, J=12.3 Hz, 5.7 Hz, 2H), 5.45 (m, 2H) and 3.72 (s, 3H);
C
3
NMR (75 MHz, CDCl ) l 231.1, 189.5, 140.8, 95.9, 91.9, 89.1, 82.5 and 56.1; IR (neat) 3250,
3
−
1
+
2
(
930, 2850, 1890, 1845, 1687, 1445, 1069 and 708 cm ; MS (m/e) 272 (M , 33.2%); [h] =+816.7
c=0.5, CHCl ). Lit. [h] =+811 (c=1, CHCl ). Analogous reaction with 4 (0.17 g, 0.56 mmol)
gave (h S)-8 (0.14 g, 90%) [h] =−809 (c=0.5, CHCl ).
D
1
4
3
D
3
6
D
3
6
6
4
.19. (p R,1S,2S)- and (p S,1S,2S)-1,2,3,4-tetrahydro-1,2-naphthalenediol chromium(0)
tricarbonyl 21 and 22
(
1R,2S)-1,2,3,4-Tetrahydro-1,2-naphthalenediol (0.41 g, 2.5 mmol) and hexacarbonyl
chromium (1.1 g, 5 mmol) were subjected to standard complexation conditions in nBu O:THF
2
(
6:1, 100 ml) for 16 h. On cooling, the mixture was filtered and the solution condensed in vacuo
to give a crude mixture of the corresponding complexes. The diastereomers were separated by
SGC (4:6 through 1:9, hexanes:ethyl acetate) to give hR 21 (0.60 g, 82%), isolated as a yellow
solid, mp 104–106°C, and hS 22 (0.09 g, 10%) isolated as a yellow solid, mp 108–110°C.
1
Complex 21: H NMR (300 MHz, CDCl ) l 5.78–5.76 (d, J=6.9 Hz, 1H), 5.54 (t, J=9.0 Hz,
3
1
H), 5.13–5.04 (m, 2H), 4.44 (d, J=4.8 Hz, 1H), 4.01–3.94 (m, 1H), 2.75 (m, 2H) and 1.98 (m,
1
3
2
H); C NMR (75 MHz, CDCl ) l 232.5, 112.3, 109.3, 95.6, 94.9, 87.1, 85.1, 68.2, 26.3 and
3
−
1
+
2
1
5.3; IR (neat) 3340 (br), 3090, 3035, 1980, 1899, 1810, 1490 and 1045 cm ; MS (m/e) 300 (M ,
7.4%), 301 (M+1, 12.8%); [h] =+15.4 (c=0.5, CHCl ); C H CrO requires: C, 52.01; H, 4.03;
D
3
13 12
5
found: C, 52.27; H, 4.23.

G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
4317
1
Complex 22: H NMR (300 MHz, CDCl ) l 5.77–5.75 (d, J=6.9 Hz, 1H), 5.53–5.50 (t, J=9
3
Hz, 1H), 5.13 (t, J=7.2 Hz, 1H), 5.04 (d, J=7.2 Hz, 1H), 4.44 (m, 1H), 4.12–4.10 (q, J=7.2 Hz,
1
3
1
1
1
H), 2.82 (br, 2H), 2.69 (m, 2H) and 1.98 (m, 2H); C NMR (75 MHz, CDCl ) l 233.2, 112.6,
3
09.4, 95.9, 95.2, 89.2, 88.6, 68.1, 67.2, 26.1 and 25.2; IR (neat) 3380 (br), 2940, 1972, 1886,
553, 1487, 1285 and 1038 cm ; MS (m/e) 300 (M , 13.3%), 299 (M−1, 5.34); [h] =−9.5
−
1
+
D
(
c=0.5, CHCl3).
4
.20. (1S,2S)-1,2-Bis(trimethylsilyloxy)-1,2,3,4-tetrahydronaphthalene chromium(0) tricarbonyl
2
3
(
1R,2S)-1,2-Bis(trimethylsilyloxy)-1,2,3,4-tetrahydronaphthalene (1.65 g, 5.34 mmol) and
chromium hexacarbonyl (2.93 g, 13.34 mmol) were subjected to standard complexation condi-
tions in nBu O:THF (6:1, 100 ml) for 48 h. On cooling, the mixture was filtered, the solution
2
condensed in vacuo, and the residual oil purified by SGC (6:4 through 1:9 hexane:ethyl acetate)
1
to give 23 (1.32 g, 55%) as a yellow oil. H NMR (300 MHz, CDCl ) l 5.46–5.41 (d, J=7.2 Hz,
3
1
2
H), 5.31–5.26 (m, 2H), 5.03–5.00 (m, 1H), 4.46 (s, 1H), 3.93–3.89 (m, 1H), 2.95–2.92 (m, 1H),
.58–2.54 (m, 1H), 2.01 (t, J=6.6 Hz, 1H), 1.73–1.67 (t, J=8.4 Hz, 1H), 0.24 (s, 9H) and 0.19
1
3
(
s, 9H); C NMR (75 MHz, CDCl ) l 233.4, 111.0, 110.3, 93.4, 92.1, 69.2, 69.0, 26.8, 24.9, 0.36
3
−
1
+
and 0.16; IR (neat) 3067, 3032, 1976, 1908, 1804, 1478 and 1043 cm ; MS (m/e) 444 (M ,
0.4%), (M−136, Cr(CO)3 group, 56.6%); [h] =−76.3 (c=0.5, CHCl ). Anal. calcd for
1
D
3
C H CrO Si : C, 51.33; H, 6.35; found: C, 51.39; H, 6.88.
1
9
28
5
2
4
.21. General photolysis and deprotection reaction procedures for mixed ligand complexes 24
The following procedure is typical for photolysis and subsequent deprotection of mixed ligand
diol complexes: 23 (0.19 g, 0.42 mmol) is dissolved in dry benzene (5 ml) in a quartz test tube,
the desired trialkyl phosphine or trialkyl phosphite added (10 equiv.), and the solution degassed.
The solution is then irradiated (Hanovia 450 W, 8 h), following which the solvent is condensed
in vacuo, the residue dissolved in MeOH (10 ml) and potassium carbonate (0.57 g, 4.16 mmol)
added. After stirring at rt for 12 h, the mixture is filtered through a plug of silica gel (EtOAc,
5
0 ml), the filtrate condensed in vacuo, and the resulting oil purified by SGC (4:6 through 1:9,
hexanes:ethyl acetate).
4
.21.1. Complex 24a
Complex 23 (0.19 g, 0.42 mmol) and tributylphosphine (1.03 ml, 4.16 mmol) gave 24a (0.15
1
g, 78%) isolated as a yellow oil; H NMR (300 MHz, CDCl ) l 5.68–5.59 (m, 1H), 5.48–5.43 (t,
3
J=7.5 Hz, 1H), 5.06 (t, J=6.9 Hz, 1H), 4.87 (m, 1H), 4.62 (s, 1H), 3.99–3.95 (d, J=8.4 Hz,
6
H), 3.79–3.76 (m, 1H), 2.92 (m, 2H), 2.73–2.70 (m, 1H), 2.35 (m, 2H), 2.06–2.02 (m, 2H), 1.82
13
(
m, 1H), 1.65 (d, J=6 Hz, 1H), 1.59 (m, 1H), 1.40–1.10 (m, 9H) and 0.91 (m, 6H); C NMR
(
2
75 MHz, CDCl ) l 240.2, 108.2, 95.6, 94.7, 89.1, 87.5, 86.9, 69.7, 66.6, 39.5, 34.1, 31.0, 27.1,
3
−
1
+
5.0 and 14.1; IR (neat) 3360 (br) cm ; MS (m/e) 474 (M , 1.2%), 446 (M−28, ꢀCO); [h] =43.5
D
(
c=0.1, CHCl ).
3
4
.21.2. Complex 24b
Complex 23 (0.34 g, 0.76 mmol) and triphenylphosphine (1.99 g, 7.58 mmol) gave 24b (0.25
1
g, 62%) isolated as a yellow oil; H NMR (300 MHz, CDCl ) l 7.72 (m, 3H), 7.54 (m, 6H), 7.40
3

4318
G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
(
2
m, 6H), 5.75 (m, 1H), 5.44 (m, 1H), 5.35 (m, 1H), 5.08 (m, 1H), 4.76 (s, 1H), 4.32 (d, 1H),
1
3
.97–2.79 (m, 2H), 2.13 (m, 2H); C NMR (75 MHz, CDCl ) l 232.4, 139.7, 133.4, 132.3, 130.9,
3
1
28.7, 127.6, 101.2, 98.7, 93.5, 92.3, 90.9, 89.9, 69.8, 67.6, 26.8 and 24.8; IR (neat) 3270 (br)
−
1
cm ; MS (m/e) 535 (M+1, 1.2%); [h] =34.1 (c=0.3, CHCl ).
D
3
4
.21.3. Complex 24c
Complex 23 (0.41 g, 0.91 mmol) and tri(o-tolyl)phosphine (2.77 g, 9.11 mmol) gave 24c (0.30
1
g, 57%) isolated as an orange oil; H NMR (300 MHz, CDCl ) l 7.46 (m, 6H), 7.32 (m, 6H),
3
5
2
1
.64 (m, 1H), 5.37 (m, 1H), 5.29 (m, 1H), 5.12 (m, 1H), 4.72 (s, 1H), 4.38 (d, J=7.2 Hz, 1H),
1
3
.93 (m, 2H), 2.24 (m, 2H), 2.09 (s, 9H); C NMR (75 MHz, CDCl ) l 233.2, 137.3, 132.4,
3
30.3, 129.1, 128.5, 128.1, 99.3, 97.4, 93.8, 90.2, 89.1, 87.6, 68.8, 67.4, 29.5, 26.3 and 24.6;
[
h] =171 (c=0.1, CHCl ).
D
3
4
.21.4. Complex 24d
Complex 23 (0.23 g, 0.51 mmol) and tri(p-tolyl)phosphine (1.56 g, 5.11 mmol) gave 24d (0.18
1
g, 63%) isolated as an orange oil; H NMR (300 MHz, CDCl ) l 7.42 (m, 6H), 7.29 (m, 6H),
3
5
2
1
.66 (m, 1H), 5.41 (m, 1H), 5.26 (m, 1H), 5.11 (m, 1H), 4.74 (s, 1H), 4.41 (d, J=6.9 Hz, 1H),
1
3
.96 (m, 2H), 2.28 (m, 2H), 1.98 (s, 9H); C NMR (75 MHz, CDCl ) l 233.2, 137.4, 132.8,
3
31.5, 128.9, 128.4, 127.9, 99.2, 97.5, 94.7, 92.4, 90.9, 87.7, 68.9, 67.2, 30.3, 26.9 and 24.8;
[
h] =141.1 (c=0.1, CHCl ).
D
3
4
.21.5. Complex 24e
Complex 23 (0.39 g, 0.87 mmol) and trimethylphosphite (1.03 ml, 8.70 mmol) gave 24e (0.17
1
g, 50%) isolated as a pale yellow oil; H NMR (300 MHz, CDCl ) l 5.52 (m, 1H), 5.43 (m, 1H),
3
5
.29 (m, 1H), 5.08 (m, 1H), 4.68 (s, 1H), 4.36 (d, J=6.3 Hz, 1H), 3.12 (m, 2H), 2.46 (m, 2H)
1
3
and 2.34 (s, 9H); C NMR (75 MHz, CDCl ) l 232.2, 99.3, 97.3, 93.9, 91.8, 91.0, 88.3, 68.8,
3
6
4
7.3, 36.5, 29.7 and 25.3; [h] =282 (c=0.1, CHCl ).
D
3
.21.6. Complex 24f
Complex 23 (0.23 g, 0.51 mmol) and triethylphosphite (0.80 ml, 5.13 mmol) gave 24f (0.12 g,
1
5
5
2
9
1%) isolated as a pale yellow oil; H NMR (300 MHz, CDCl ) l 5.48 (m, 1H), 5.41 (m, 1H),
3
.33 (m, 1H), 5.11 (m, 1H), 4.73 (s, 1H), 4.44 (d, J=6.6 Hz, 1H), 4.24 (m, 6H), 2.46 (m, 2H),
1
3
.21 (m, 2H) and 1.47 (t, J=8.7 Hz, 9H); C NMR (75 MHz, CDCl ) l 233.4, 102.7, 99.8, 97.4,
3
3.3, 92.5, 89.2, 68.4, 66.1, 49.8, 33.5, 31.7 and 23.6; [h] =365 (c=0.1, CHCl ).
D
3
4
.21.7. Complex 24g
Complex 23 (0.21 g, 0.47 mmol) and tributylphosphite (1.27 ml, 4.68 mmol) gave 24g (0.24 g,
1
9
9%) isolated as a pale yellow oil; H NMR (300 MHz, CDCl ) l 5.73 (d, J=6.6 Hz, 1H), 5.55
3
(
1
d, J=7.2 Hz, 1H), 5.18 (m, 1H), 5.11 (d, J=5.1 Hz, 1H), 4.71 (s, 1H), 4.22 (m, 6H), 3.14 (m,
H), 2.92 (m, 1H), 2.34 (m, 2H), 2.08 (m, 1H), 2.01–1.54 (m, 12H) and 1.23 (m, 9H); C NMR
13
(
2
75 MHz, CDCl ) l 240.2, 101.5, 98.7, 97.3, 94.5, 93.4, 89.9, 70.2, 68.8, 55.7, 48.5. 34.8, 30.8,
3
−
6.9 and 22.5; MS (m/e) 521 (M , 1.0%), 524 (M+2, 1.0%); [h] =61.2 (c=0.5, CHCl ).
D
3
4
.21.8. Complex 24h
Complex 23 (0.63 g, 1.43 mmol) and triphenylphosphite (3.74 ml, 14.26 mmol) gave 24h (0.80
1
g, 96%) isolated as a pale yellow oil; H NMR (300 MHz, CDCl ) l 7.40–7.15 (m, 15H), 5.68
3

G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
4319
(
(
m, 1H), 5.38 (m, 2H), 5.21 (m, 1H), 4.70 (s, 1H), 4.35 (m, 1H), 4.18–4.12 (m, 1H), 3.97–3.84
1
3
m, 1H), 3.52 (m, 1H), 2.42 (m, 1H); C NMR (75 MHz, CDCl ) l 233.3, 135.8, 131.5, 128.8,
3
1
25.8, 120.6, 108.0, 104.1, 94.9, 93.0, 91.6, 87.9, 85.2, 72.3, 66.7, 38.6 and 25.6; [h] =80.4
D
(
c=0.1, CHCl ); C H CrO P requires C, 61.86; H, 4.67; found: C, 61.93; H, 4.82.
3
30 27
7
6
4
.22. (p R,1R)-1,2,3,4-Tetrahydronaphthyl alcohol chromium(0) tricarbonyl 26
(
1S)-1,2,3,4-Tetrahydronaphthylalcohol 25 (0.17 g, 1.17 mmol) and hexacarbonyl chromium
(
0.65 g, 2.94 mmol) were subjected to standard complexation conditions in nBu O: THF (6:1, 70
2
ml) for 16 h. On cooling, the mixture was filtered, the solution condensed in vacuo, and the
resulting residue purified by SGC (60:40 through 10:90 hexanes:EtOAc) to give 26 (0.20 g, 61%)
1
5
1
as a yellow solid, mp 137–138°C (Lit. 140°C). H NMR (300 MHz, CDCl ) l 5.85 (s, 1H), 5.52
3
(
2
s, 1H), 5.14 (m, 2H), 4.52 (s, 1H), 2.71–2.63 (m, 2H), 2.09 (m, 1H) 1.96 (m, 1H) and 1.71 (m,
1
3
H); C NMR (75 MHz, CDCl ) l 233.3, 95.1, 93.4, 90.1, 88.9, 66.6, 32.1, 27.5 and 19.2; IR
3
(
neat) 3450 (br); [h] =25.5 (c=0.5, CHCl ).
D
3
6
4
.23. (p R,1S,2S)-Indane-1,2-diol chromium(0) tricarbonyl 19
Under standard complexation conditions, (1R,2S)-1,2, indanediol 18 (0.59 g, 3.95 mmol) gave
1
1
9 (0.93 g, 82%) isolated as a yellow solid, mp 118–120°C (dec.); H NMR (300 MHz, CDCl )
3
l 5.63 (m, 1H), 5.40 (s, 1H), 5.28 (d, J=8.4 Hz, 2H), 4.78 (s, 1H), 4.37 (s, 1H), 3.15 (br, 2H),
1
3
3
9
.05 (m, 1H) and 2.86 (d, J=12.9 Hz, 1H); C NMR (75 MHz, CDCl ) l: 232.8, 112.1, 109.8,
3
4.1, 90.2, 89.6, 87.7, 74.0, 70.3 and 37.8; IR (neat) 3338 (br, ꢀOH); [h] =+23.1 (c=0.5,
CHCl ); C H CrO requires: C, 50.36; H, 3.53; found: C, 50.59; H, 3.70.
D
3
12 10
5
4
.24. General procedure for catalytic enantioselective Diels–Alder reactions
Lewis acid (0.33 mmol) is added slowly to a pre-cooled (−78°C) solution of the catalyst
precursor (0.33 mmol) in methylene chloride (5 ml). The mixture is allowed to warm to ambient
temperature over a period of 3 h, then re-cooled to −78°C. Freshly distilled dienophile (1.67
mmol) is added rapidly by syringe and the mixture stirred for a further 15 min, then freshly
distilled diene (8.3 mmol) added and the mixture stirred for 3 h at −78°C. The reaction mixture
is warmed to 0°C, quenched by addition of NaHCO (sat. 2×20 ml), then extracted with
3
methylene chloride (1×10 ml). The organic extracts are dried (Na SO ) and condensed in vacuo,
2
4
and the resulting residue is purified by SGC (9:1 hexane:ether) to recover cycloadducts together
with catalyst precursor. Exo/endo ratios of cycloadducts are determined from NMR spectra.
Enantiomeric excesses are calculated either by NMR analysis using Eu(hfc) chiral shift reagent,
3
10
or by derivatization [(2R,4R)-(−)-pentane diol] followed by GC analysis. Stereochemical
16
assignments were confirmed by optical rotation of cycloadducts.
Acknowledgements
We thank the PRF (administered by the American Chemical Society) for financial support of
this work (33920-AC1).

4320
G. B. Jones et al. / Tetrahedron: Asymmetry 11 (2000) 4303–4320
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