Organotransition-metal-modified sugars Part 17. Glucal-derived carbene complexes: syhthesis and diastereoselective benzannulation

Article abstract of DOI:10.1016/S0022-328X(00)00748-8

The addition of triisopropylsilyl and/or isopropylidene-protected 1-lithio-D-glucals prepared in situ from stannylated precursors 5 and 6 to hexacarbonyl chromium followed by methylation affords D-arabino-hex-1-enopyranosylcarbene complexes 7 and 8. They undergo a diastereoselective benzannulation upon reaction with tolan and 3-hexyne to give polyoxygenated chromans 9 to 12 in good yields and moderate diastereomeric excess values. The confirmation of the glucal moiety in the carbene ligand and in the chroman skeleton is controlled by the nature of the protective groups. 1H-NMR studies and single crystal X-ray analyses indicate a ⁵H₄-conformation of the sugar moiety for the triisopropylsilyl compounds 7, 9a,b, 10a,b and 11 and ⁴H₅-conformation for the isopropylidene derivatives 8 and 12a-c in solution, and further for 8 and 12a in the solid state.

Full text of DOI:10.1016/S0022-328X(00)00748-8

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Journal of Organometallic Chemistry 621 (2001) 77–88
Organotransition-metal-modified sugarsꢀ
Part 17. Glucal-derived carbene complexes: synthesis and
diastereoselective benzannulation
Karl Heinz Do¨tz a,*, Frank Otto a, Martin Nieger b
a Kekule´-Institut fu¨r Organische Chemie und Biochemie der Rheinischen Friedrich-Wilhelms-Uni6ersita¨t Bonn, Gerhard Domagk-Straße 1,
D-53121 Bonn, Germany
b Institut fu¨r Anorganische Chemie der Rheinischen Friedrich-Wilhelms-Uni6ersita¨t Bonn, Gerhard Domagk-Straße 1, D-53121 Bonn, Germany
Received 23 August 2000; accepted 15 September 2000
Dedicated to Professor Henri Brunner on the occasion of his 65th birthday
Abstract
The addition of triisopropylsilyl and/or isopropylidene-protected 1-lithio-
D-glucals prepared in situ from stannylated precursors
5 and 6 to hexacarbonyl chromium followed by methylation affords -arabino-hex-1-enopyranosylcarbene complexes 7 and 8.
D
They undergo a diastereoselective benzannulation upon reaction with tolan and 3-hexyne to give polyoxygenated chromans 9 to
12 in good yields and moderate diastereomeric excess values. The conformation of the glucal moiety in the carbene ligand and
1
in the chroman skeleton is controlled by the nature of the protective groups. H-NMR studies and single crystal X-ray analyses
5
4
indicate a H4-conformation of the sugar moiety for the triisopropylsilyl compounds 7, 9a,b, 10a,b and 11 and H5-conformation
for the isopropylidene derivatives 8 and 12a–c in solution, and further for 8 and 12a in the solid state. © 2001 Elsevier Science
B.V. All rights reserved.
applications. Since organometallic reagents have a great
potential in stereoselective synthesis, we focused on an
organometallic modification of the multifunctional car-
bohydrates [10]. Prior to our work, the activation of the
anomeric center towards C-glycosidation by transition
metals has been mainly restricted to samarium and
palladium [11]. Glycosyl complexes of iron [12] and
manganese [13] have been synthesized, but their appli-
cation in C-glycosidation was hampered by the low
reactivity or by the high-pressure conditions required.
Recently, a tungsten-carbonyl-catalyzed cycloisomeriza-
tion of highly functionalized alkynes has been applied
to the synthesis of O-glycosides [14].
Recently, we have elaborated complementary syn-
thetic routes to metal-carbene-functionalized carbohy-
drates based on a metal carbonyl electrophile–sugar
nucleophile combination or vice versa [10], and demon-
strated their application in diastereoselective Diels–
Alder [15] and C-glycosidation reactions [16], as well as
in the formation of iminoglycosylidenes [17].
Chromium aryl- and vinyl-carbenes are known to un-
1. Introduction
Carbohydrates are ubiquitous naturally occurring
compounds and play an eminent role in chemistry and
biology [1]. They are involved in molecular recognition
at cell walls [2], intracellular enzyme transport [3],
infections [4] and cell adhesion [5]. In addition, polysac-
charides serve as materials for the storage and supply of
energy and for construction [6]. A major area of syn-
thetic carbohydrate chemistry concentrates on glycosi-
dation reactions. Although a variety of powerful
O-glycosidation methods have been developed [7], the
elaboration of stereoselective protocols remains an on-
going challenge [8]. In contrast to O-glycosides, their
C-analogues are inherently stable towards hydrolysis [9]
and, thus, they are promising candidates for therapeutic
ꢀ For part 16, see B. Weyershausen et al., J. Organomet. Chem.
602 (2000) 37.
* Corresponding author. Tel.: +49-228-735609; fax: +49-228-
735813.
E-mail address: doetz@uni-bonn.de (K.H. Do¨tz).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00748-8

78
K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
dergo benzannulation upon reaction with alkynes [18].
We have used this methodology in the synthesis of
chromium-labeled polyoxygenated chromans, and report
now on the synthesis of glucal-derived chromium car-
benes and their diastereoselective benzannulation.
The 4,6-O-isopropylidene acetal [21b,22] and 3-triiso-
propylsilyl groups [21] are compatible with the excess of
tert-butyl lithium required for C-1 deprotonation of the
glucal and with the subsequent trapping of the glucal
anion by tri-n-butyl tin chloride [21a] (Scheme 1).
The conformation of the glucals 2–8 depends on the
nature of the protective group [23]. The coupling pattern
1
5
2. Results and discussion
in the H-NMR spectrum indicates a H4-conformation
for the tri-TIPS-protected compounds 2, 5, and 7
2.1. Synthesis of chromium glucal carbenes
(smaller coupling constants of ca. 1.5–2.0 Hz for 3JH-3,H-4
,
4
4
3JH-4,H-5, JH-2,H-4, and JH-3,H-5 and a medium coupling
The Fischer route, based on the sequential addition of
an organolithium nucleophile and an alkylative elec-
trophileacrossametalcarbonylligand, isthemostgeneral
access to metal carbenes [19]. Along this approach the
3
4
constant of ca. 5.0–5.5 Hz for JH-3,H-2) and a H5-con-
formation for the 4,6-O-isopropylidene-protected glucal
derivatives 3, 4, 6, and 8 (smaller coupling constant of
ca. 1.9–2.4 Hz for 3JH-2,H-3 and larger coupling constants
hydroxy substituents of
D
-glucal 1 have to be suitably
3
of ca. 7.0–8.0 Hz and ca. 10.5 Hz for JH-3,H-4 and
protected by isopropylidene and/or triisopropylsilyl
groups compatible with the subsequent organometallic
protocol. A clean anomeric lithiation is best performed
by a metalation/transmetalation sequence [11,20,21a,b];
lithiation of the protected glucal with tert-butyl lithium
followed by stannylation with tri-n-butyl tin chloride af-
forded excellent yields of the stannylated glucals 5 and 6,
which can be stored for several months at 2°C. Tin–
lithium exchange occurs at −78°C with n-butyl lithium;
addition of the resulting lithioglucals to hexacarbonyl
chromium at −40°C generated the acyl chromate inter-
mediates, which were alkylated with trimethyloxonium
tetrafluoroborate to give glucal carbene complex 7 as a
red oil or 8 as a red solid.
3JH-4/H-5; no J couplings observable) (Table 1).
4
The molecular structure of the TIPS/isopropylidene-
protected glucal carbene complex 8 has been established
by single crystal X-ray analysis (Fig. 1). It reveals a similar
4H5-conformation in the solid state as observed for it and
its precursors 3, 4, and 6 in solution. The carbene complex
adopts a Z-configuration for the carbene–oxygen bond
and a transoid conformation across the vinylcarbene
chromium moiety.
2.2. Diastereoselecti6e benzannulation
We wanted to take advantage of the chiral information
provided by the sugar skeleton of chromium glucals 7
and 8 and aimed at a diastereoselective benzannula-
The choice of protective groups is crucial and limited
by the basic conditions applied in the stannylation step.
Scheme 1. Syntheses of the carbene complexes 7 and 8 starting from
D-glucal.

K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
79
Table 1
Coupling constants and conformations of the prepared glucal derivatives 2–8
Compound
3JH-2,H-3 (Hz)
3JH-3,H-4 (Hz)
3JH-4,H-5 (Hz)
4JH-2,H-4 (Hz)
4JH-3,H-5 (Hz)
Conformation
2
3
4
5
6
7
8
5.36
1.96
1.84
5.07
1.89
5.47
2.35
–
–
7.01
–
7.35
–
–
–
1.78
–
5H4
4H5
4H5
5H4
4H5
5H4
4H5
absent
absent
1.69
absent
1.49
absent
absent
–
absent
–
10.43
ꢀ2
10.44
ꢀ2
–
7.82
absent
absent
tion in order to generate an additional chiral plane
upon coordination of the Cr(CO)3 fragment to the
newly formed hydroquinone ring. The diastereoselectiv-
ity of the benzannulation is expected to be controlled
by the conformation of the glucal, which is known to
depend on the nature of the protective groups [23].
First, we studied the reaction of carbene complex 7
spectroscopy. The coupling patterns of the glucal pro-
tons of 9a,b, 10a,b, and 12a–c resemble those observed
for carbene complexes 7 and 8, suggesting that the
4H5-conformation did not change upon benzannulation.
The configuration as defined by the coordination of the
chromium fragment to the arene was first tentatively
assigned on the basis of coordination shifts. As a
consequence of the anisotropic effect arising from the
Cr(CO)3-tripod glucal, protons located at the same face
of the chiral plane as the chromium fragment are
expected to resonate at lower field compared with those
in the demetalated benzannulation product (Table 2)
[24].
5
with 3-hexyne. The H4-conformation of the glucal part
combined with the bulky TIPS-groups was supposed to
direct the benzannulation in a highly stereoselective
way. After chromatographic workup we obtained a
39% yield of a diastereopure chroman–Cr(CO)3 com-
plex along with a 31% yield of the uncoordinated
chroman. The benzannulation of 7 with tolan gave an
increased yield of the chroman–Cr(CO)3 complex. In
addition to the expected benzannulation product 10a
(46%) and a minor amount of uncoordinated chroman
10b (7%), another chroman–Cr(CO)3 complex 11 (13%)
was obtained but could not be isolated as a pure
compound (Scheme 2). IR and NMR spectroscopic
data suggest the formation of an isomer of 10a in which
the Cr(CO)3 fragment is attached to one of the phenyl
rings originating from tolan. So far, we cannot decide
whether it is formed via an intermolecular decomplexa-
tion/recomplexation sequence or an intramolecular
haptotropic metal migration across the biaryl bond.
Chromatographic workup afforded the chroman com-
plexes 9a and 10a as single diastereomers; within the
accuracy of NMR spectroscopy, no minor diastereo-
mers bearing the Cr(CO)3 fragment attached to the
opposite face of the arene could be detected.
The tentative assignment of the configuration con-
cerning the chiral plane on the basis of NMR-coordina-
tion shifts was further supported by a study of the
molecular structure of the major diastereomer 12a in
the solid state. Cubic crystals, grown from an n-hexane
solution cooled to −30°C, allowed for an unambigu-
ous assignment of the configuration and the conforma-
tion by a single-crystal X-ray analysis. This confirmed
4
that the H5-conformation favored in solution is also
The reaction of the 4,6-O-isopropylidene-protected
glucal carbene complex 8 with 3-hexyne carried out in
tert-butyl methyl ether at 55°C afforded a 79% overall
yield of benzannulation products. Along with the unco-
ordinated chroman 12c (33%), the diastereomeric chro-
man complexes 12a and 12b were isolated after
chromatographic workup in 35% and 11% yields re-
spectively, indicating a diastereomeric excess (d.e.) of
54% as determined by integration of the 1H-NMR
spectrum and high performance liquid chromatography
(HPLC) (Scheme 3).
Fig. 1. Molecular structure of carbene complex 8. Selected bond
,
lengths (A): C1ꢀC2, 1.331(5); C1ꢀC11, 1.507(5); C11ꢀCr1, 2.032(4);
C1ꢀO1, 1.380(4); C11ꢀO12, 1.320(4); Cr1ꢀC1a, 1.874(5); Cr1ꢀC1b,
1.879(6); Cr1ꢀC1c, 1.889(6); Cr1ꢀC1d, 1.900(6); Cr1ꢀC1e, 1.874(6);
selected bond angles (°): C1ꢀC2ꢀC3, 125.1(4); C2ꢀC1ꢀC11, 125.9(4);
C1ꢀC11ꢀCr1, 123.6(3); C1aꢀCr1ꢀC11, 175.5(2); C1bꢀCr1ꢀC11,
93.8(2); C1cꢀCr1ꢀC11, 89.5(2); C1dꢀCr1ꢀC11, 90.4(2); C1eꢀCr1ꢀC11,
96.1(2); selected torsion angles (°): O1ꢀC1ꢀC2ꢀC3, 0.9(9);
C1ꢀC2ꢀC3ꢀC4, −8.5(7); C2ꢀC3ꢀC4ꢀC5, 38.5(6); C3ꢀC4ꢀC5ꢀO1,
−63.3(5); C1ꢀO1ꢀC5ꢀC4, 53.3(5); C5ꢀO1ꢀC1ꢀC2, −21.4(8); C2ꢀC1ꢀ
C11ꢀCr1, 167.3(5); O1ꢀC1ꢀC11ꢀCr1, −9.7(7); C1aꢀCr1ꢀC11ꢀC1,
The conformation and the configuration of the benz-
−43(3);
C1bꢀCr1ꢀC11ꢀC1,
−131.2(4);
C1cꢀCr1ꢀC11ꢀC1,
1
annulation products have been analyzed by H-NMR
−41.3(5); C1dꢀCr1ꢀC11ꢀC1, 50.5(5); C1eꢀCr1ꢀC11ꢀC1, 138.4(4).

80
K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
Scheme 2. Benzannulation of the TIPS-protected glucal carbene complex 7 with 3-hexyne and tolan.
Scheme 3. Benzannulation of the isopropylidene-protected glucal carbene complex 8 with 3-hexyne.
Table 2
Chemical shifts (ppm) of the glucal protons of the benzannulation products, 9a,b and 10a,b in CD2Cl2; 12a–c in CDCl3 (H-1, H-1% for the
tri-TIPS-protected compounds and H-1e, H-1a for the TIPS/isopropylidene-protected compounds)
Proton
H-1 (H-1e)
H-1% (H-1a)
H-2
H-3
H-4
l(9a)
l(9b)
l(9a)−l(9b)
l(10a)
l(10b)
l(10a)−l(10b)
l(12a)
l(12b)
l(12c)
l(12a)−l(12c)
l(12b)−l(12c)
4.31
4.11
0.20
4.41
4.21
0.20
4.04
4.26
4.00
0.26
4.41
4.10
0.31
3.98
4.47
4.41
0.06
4.60
4.52
0.08
3.90
4.22
3.83
0.07
0.39
4.42
4.35
0.07
4.52
4.44
0.8
4.49
–
4.12
0.37
–
4.93
5.03
−0.10
5.09
5.13
−0.04
5.23
5.48
5.26
−0.03
−0.02
4.09
−0.05
–
3.95
0.03
–
preferred in the solid state, as demonstrated by the
torsion angles within the glucal moiety, and further
established that the Cr(CO)3 fragment is coordinated to
the same face of the arene as the bulky TIPSO group at
C-4 (Fig. 2). As known for comparable naphthohy-
droquinone complexes [25], the chromium atom is not
coordinated symmetrically to the center of the arene
ring but is shifted towards the periphery away from the
adjacent pyran ring. The distances of the Cr atom to
,
the bridging ring carbon atoms C4a (2.2478(17) A) and
,
,
C8a (2.2640(16) A) exceed those to C6 (2.2335(16) A)
,
and C7 (2.2039(16) A). The Cr(CO)3-tripod deviates

K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
81
from coplanarity with the coordinated arene ring and is
tilted away from the pyran ring, as indicated by the
bond angles C4aꢀCr1ꢀC1b (95.09(7)°) and C8aꢀCr1ꢀ
C1b (89.45(7)°) versus C6ꢀCr1ꢀC1c (92.19(7)°) and
C7ꢀCr1ꢀC1a (87.29(7)°). The orientation of the
Cr(CO)3-tripod in the solid state is turned about 45°
compared with that usually found for Cr(CO)3 com-
plexes of naphthalene and naphthohydroquinones [26];
one CO group of compound 12a lies above the pyran
ring, securing a minimization of steric interaction be-
tween the bulky TIPS group at C-4 and the carbonyl
ligands.
Fig. 2. Molecular structure of the major diastereomer 12a. Selected
The preferred coordination of the metal fragment
from the more crowded face is surprising at first sight,
but may be addressed in terms of the mechanism of the
[3+2+1] benzannulation, as supported by experimen-
tal and theoretical evidence [18,27] (Scheme 4). The
reaction is believed to start with loss of a cis-carbonyl
ligand (a) followed by coordination of the alkyne at the
vacant coordination site [28] (b). The CꢀC bond forma-
tion is initiated by the insertion of the alkyne into the
chromium–carbene bond, which generates a s,p-allyl
complex (equivalent to a vinylcarbene complex) bearing
the metal fragment above or below the allyl plane (c).
Since the bulky glucal moiety is expected to favor the
coordination of the alkyne from the less-congested side
,
bond lengths (A): C4aꢀC5, 1.415(2); C4aꢀC8a, 1.432(2); C8ꢀC8a,
1.405(2); C7ꢀC8, 1.420(2); C6ꢀC7, 1.407(2); C5ꢀC6, 1.431(2);
Cr1ꢀC4a, 2.2478(17); Cr1ꢀC8a, 2.2640(16); Cr1ꢀC5, 2.2516(16);
Cr1ꢀC8, 2.2306(15); Cr1ꢀC6, 2.2335(16); Cr1ꢀC7, 2.2039(16);
Cr1ꢀZAr, 1.7321(7); selected bond angles (°): ZArꢀCr1ꢀC1a, 125.7(1);
ZArꢀCr1ꢀC1b, 126.9(1); ZArꢀCr1ꢀC1c, 125.1(1); C4aꢀC8aꢀCr1,
37.00(6); C8aꢀC8ꢀCr1, 36.41(6); C8ꢀC7ꢀCr1, 37.36(6); C7ꢀC6ꢀCr1,
36.96(6); C6ꢀC5ꢀCr1, 37.20(6); C5ꢀC4aꢀCr1, 36.65(6); C4aꢀCr1ꢀ
C1b, 95.09(7); C8aꢀCr1ꢀC1b, 89.45(7); C6ꢀCr1ꢀC1c, 92.19(7);
C7ꢀCr1ꢀC1a, 87.29(7); selected torsion angles (°): C4ꢀC4aꢀC8aꢀO1,
1.1(2); C3ꢀC4ꢀC4aꢀC8a, −20.6(2); C2ꢀC3ꢀC4ꢀC4a, 51.12(17); O1ꢀ
C2ꢀC3ꢀC4, −67.76(17); C8aꢀO1ꢀC2ꢀC3, 47.79(18); C2ꢀO1ꢀ
C8aꢀC4a, −14.7(2); C7ꢀC8ꢀC8aꢀC4a, 1.4(2); C5ꢀC4aꢀC8aꢀC8,
−5.4(2); C8aꢀC4aꢀC5ꢀC6, 6.2(2); C4aꢀC5ꢀC6ꢀC7, −2.8(2);
C5ꢀC6ꢀC7ꢀC8, −1.5(2); C6ꢀC7ꢀC8ꢀC8a, 2.1(2).
Scheme 4. Supposed mechanism of the [3+2+1]-benzannulation.

82
K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
opposite the bulky TIPSO substituent, the alkyne inser-
tion places the chromium fragment towards the TIPSO
group. Provided that no further inversion of configura-
tion occurs associated with the subsequent carbonyl
insertion (d), electrocyclization at the chromium tem-
plate (e) and rearomatization (f) [29], the configuration
at the chiral plane observed in the final benzannulation
product is determined by the alkyne insertion,
which — along these lines — is to be regarded as the
stereodifferentiating step of the reaction sequence.
4.2. Instrumentation
IR: Nicolet Magna 550 FT-IR. NMR: Bruker DRX
500 and AM-400. MS (FAB, EI): Kratos MS-50 and
Concept 1H. Elemental analysis: Elementar Analysen-
systeme Vario EL. HPLC: Knauer Wellchrom injection
valve A0258, pump K-1001, solvent organizer K-1500,
UV-detector K-2600, column Knauer Eurospher 100
RP-18 100 Si.
4.3. X-ray crystallographic studies of 8 and 12a
Crystallization from n-hexane at −30°C provided
red crystals of 8 and yellow crystals of 12a which were
subjected to single-crystal X-ray analysis. Data were
collected on a Nonius KappaCCD at 123 K. The struc-
tures were solved by direct methods (SHELXS-97) [31].
The non-hydrogen atoms were refined anisotropically
on F2 (SHELXL-97) [32]. H atoms were refined isotropi-
cally using a riding model. The absolute structure was
determined by refinement of Flack’s parameter x [33].
An empirical absorption correction was applied (8:
3. Conclusions
Glucals serve as valuable chiral information for the
diastereoselective benzannulation of a,b-unsaturated
chromium carbene complexes upon reaction with al-
kynes. The conformation of the pyranose ring is con-
trolled by the nature of the protective groups irrespec-
tive of stannylation or metal carbene functionalization
at C-1 and of benzannulation to give polyoxygenated
chroman Cr(CO)3 complexes. The conformation in so-
Tmax/min=0.9758/0.8439;
12a:
Tmax/min=0.9533/
5
lution is determined as H4 for the TIPS substitution
pattern while the more rigid 4,6-O-isopropylidene pro-
tection favors the H5 conformation, and is unchanged
0.8676). Further details are given in Table 3. Atomic
coordinates and equivalent isotropic displacement
parameters are given in Tables 4 and 5 respectively.
4
in the solid state as established for the 4,6-O-isopropyli-
dene glucal carbene complex and its annulation product
with 3-hexyne. The benzannulation proceeds under
mild conditions with good overall chemical yields and
considerable to excellent diastereoselective excess.
Mechanistic considerations based on a stereodifferenti-
ating alkyne insertion into the chromium carbene bond
may rationalize the preferred formation of the sterically
more congested diastereomeric chroman complexes.
The diastereoselective benzannulation of glycal
chromium carbenes provides a straightforward access
to the skeleton of polyoxygenated chromans as present
in cryptosporins, which exhibit a weak antibiotic activ-
ity [30].
4.4. Reagents
4.4.1. Synthesis of glucals 2–6
4.4.1.1. 1,5-Anhydro-2-desoxy-3,4,6-tri-O-triisopropyl-
silyl-
of TIPSOTf were added dropwise at 0°C to a solution
of 3.65 g (25.00 mmol) of -glucal and 19.2 ml
D
-arabino-hex-1-enitol (2). 30.2 ml (112.50 mmol)
D
(165.00 mmol) of 2,6-lutidine in 25 ml of CH2Cl2. The
mixture was stirred for 60 min at room temperature
(r.t.) and then diluted with 50 ml CH2Cl2. After
quenching the reaction with 50 ml of water, the
aqueous layer was extracted three times with 50 ml of
CH2Cl2. Washing the combined organic layers three
times with water and once with a saturated solution of
brine gives 2; drying over MgSO4 and removal of the
solvent afforded a crude product which was purified by
column chromatography with petroleum ether–
dichloromethane (1:1) as eluent to give 6.65 g
4. Experimental
4.1. General reaction conditions
(19.41 mmol, 78%) of a colorless oil.
3
All reactions were carried out under argon. The
solvents used for reactions and chromatography were
dried (dried and distilled over lithium aluminum chlo-
ride: diethyl ether, tert-butyl methyl ether, petroleum
ether, methylene chloride; dried and distilled over
potassium: tetrahydrofuran). Chromatography was per-
formed with silica gel (Merck type 60, 0.63–0.200 mm).
1H-NMR (500 MHz, CDCl3): l=6.33 (d, JH-1,H-2
=
6.36 Hz, 1H, H-1), 4.78 (ddd, 3JH-2,H-1=6.36 Hz,
4
3JH-2,H-3=5.36 Hz, JH-2,H-4 1.78 Hz, 1H, H-2), 4.22 (m,
2
3
1H, H-5), 4.06 (dd, JH-6,H-6%=11.33 Hz, JH-6,H-5
=
7.95 Hz, 1H, H-6), 4.03 (m, 1H, H-4), 3.93 (m, 1H,
2
3
H-3), 3.83 (dd, JH-6%,H-6=11.33 Hz, JH-6%,H-5=3.77 Hz,
1H, H-6%), 0.11–0.09 (m, 63H, ꢀSi[CH(CH3)2]3) ppm.
13C-NMR (125 MHz, CDCl3): l=142.9 (C-1), 100.3
(C-2), 80.7, 70.2, 65.0, 62.0, (4C, C-3, C-4, C-5, C-6),
1
D.e. values were determined by H-NMR spectroscopy
and HPLC.

K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
83
3JH-2,H-1=6.08 Hz, 3JH-2,H-3=1.96 Hz, 1H, H-2), 4.19
Table 3
Crystallographic data and summary of data collection and refinement
of 8 and 12a
(m, 1H, H-3), 3.83–3.55 (m, 4H, H-4, H-5, H-6a,
3
H-6e), 3.47 (d, J=4.69 Hz, 1H, ꢀOH), 1.40, 1.38 (s,
6H, (CH3)2Cꢀ) ppm. 13C-NMR (125 MHz, CDCl3):
l=143.5 (C-1), 103.9 (C-2), 99.5 [(CH3)2Cꢀ]; 73.2,
69.0, 66.4, 61.2 (4C, C-3, C-4, C-5, C-6), 28.7, 18.8 (2C,
(CH3)2Cꢀ) ppm. EI-MS (70 eV): m/z (%)=186.0 (21)
[M+], 171.0 (31) [M+−CH3], 114.0 (54) [M+−
C3H4O2].
8
12a
Formula
Mr
Crystal system
Space group
C25H36CrO10Si
576.63
C
30H46CrO9Si
630.76
orthorhombic
P212121 (no. 19)
11.1512(7)
11.2972(8)
23.0370(17)
90, 90, 90
2902.1(3)
orthorhombic
P212121 (no. 19)
8.8866(2)
17.6827(4)
20.4121(3)
90, 90, 90
3207.54(11)
4
,
a (A)
,
b (A)
,
c (A)
4.4.1.3. 1,5-Anhydro-2-desoxy-4,6-O-isopropylidene-3-
h, i, k (°)
O-(triisopropylsilyl- -arabino-hex-1-enitol (4). 4 ml
D
3
,
V (A )
Z
(14.90 mmol) TIPSOTf were added dropwise to a solu-
tion of 1.83 g (9.83 mmol) of glucal 3 and 2.5 ml of
2,6-lutidine in 11 ml of CH2Cl2. The solution was
stirred for 30 min at r.t. before the reaction was
4
Crystal size
0.25×0.15×0.03
0.25×0.25×0.10
(mm3)
zcalc (g cm−3
)
1.32
0.486
1216
1.30
0.443
1344
v (mm−1
F(000)
)
Diffractometer
Radiation
Nonius KappaCCD
Mo–Ka
0.710 73
123(2)
Nonius KappaCCD
Mo–Ka
0.710 73
123(2)
Table 4
Atomic coordinates (×104) and equivalent isotropic displacement
2
3
,
u (A)
,
parameters (A ×10 ) for 8
T (K)
a
Max. 2[ (°)
Index range
50.0
56.6
x
y
z
Ueq
−135h513,
−135k513,
−275l527
34 244
−115h511,
−235k523,
−275l526
44 382
Cr1
C1a
O1a
C1b
O1b
C1c
O1c
C1d
O1d
C1e
O1e
O1
C1
C2
C3
C4
C5
C6
O7
C8
2444(1)
2566(5)
2700(4)
3656(5)
4390(4)
3622(5)
4351(3)
1185(5)
413(3)
8086(1)
7728(3)
7534(3)
9208(5)
9863(4)
3906(6)
6177(4)
6964(6)
6295(4)
9217(6)
9883(4)
6301(2)
7403(4)
7541(4)
6553(3)
5408(3)
5375(4)
4205(3)
3271(3)
3295(4)
2455(5)
2948(5)
4435(3)
8379(3)
9374(2)
10 529(3)
6787(3)
7150(1)
8813(3)
9439(5)
9308(6)
6632(5)
6918(6)
5308(5)
6486(5)
5147(5)
6916(6)
2114(1)
1322(2)
835(2)
35(1)
40(1)
63(1)
36(2)
59(1)
40(2)
62(2)
40(2)
63(2)
40(2)
53(1)
36(1)
31(1)
31(1)
31(1)
33(1)
33(1)
38(1)
43(1)
44(1)
58(2)
56(2)
40(1)
31(1)
39(1)
43(1)
32(1)
32(1)
30(1)
45(2)
45(2)
34(2)
52(2)
44(2)
39(2)
59(2)
55(2)
No. of data
No. of unique
data
Parameters
x
R(F) for
I\2|(I)
wR2(F2) for all
data
5045
7934
1978(3)
1848(2)
2226(2)
2266(2)
2189(3)
2204(2)
1926(3)
1768(2)
3180(1)
3430(2)
3996(2)
4430(2)
4136(2)
3531(2)
3248(2)
3597(1)
4192(2)
4491(3)
4267(3)
4447(1)
2984(2)
3285(1)
3010(2)
4917(1)
5596(1)
5646(2)
5393(2)
5387(3)
5983(3)
6632(3)
5896(3)
5840(3)
5824(3)
6455(3)
334/0
0.01(4)
0.054
373/1
−0.01(1)
0.031
0.101
0.92
0.075
0.99
1278(5)
556(3)
Goodness of fit
2323(3)
2456(5)
2651(4)
2736(4)
2378(5)
2843(4)
2551(6)
3032(3)
2677(6)
3509(5)
1354(5)
2886(3)
2414(4)
2407(3)
2487(5)
1993(2)
2326(1)
2448(5)
1348(4)
3594(4)
959(4)
on F2
18.1–18.0 (18C, ꢀSi[CH(CH3)2]3), 12.5–12.0 (9C,
ꢀSi[CH(CH3)2]3) ppm. EI-MS (70 eV): m/z (%)=571.5
(100) [M+−C3H7], 397.2 (67) [M+−C3H7−
C9H21SiOH], 385.2 (62) [M+−C13H29SiO].
C9
C10
O11
C11
O12
C12
O3
4.4.1.2. 1,5-Anhydro-2-desoxy-4,6-O-isopropylidene-
arabino-hex-1-enitol (3). solution of 4.24 g
(22.17 mmol) -glucal and 13.0 ml 2,2-
D-
A
D
dimethoxypropane in 40 ml DMF was adjusted to pH 3
by addition of p-toluene sulfonic acid. The solution was
stirred for 45 min at 0°C (control by TLC, ethyl ace-
tate–diethyl ether 1:1). The reaction was quenched with
100 ml of aqueous NaHCO3. The aqueous layer was
extracted three times with 100 ml of diethyl ether; the
combined organic layers were washed three times with
100 ml water and dried over MgSO4. Chromatography
(same eluent as used for TLC) gave 2.07 g (11.12 mmol,
50%) of 3 as a colorless oil.
Si1
C13
C14
C15
C16
C17
C18
C19
C20
C21
912(4)
670(4)
3782(4)
3852(5)
4180(4)
1H-NMR (500 MHz, CDCl3): l=6.15 (dd, JH-1,H-2
3
a Ueq is defined as one-third of the trace of the orthogonalized Uij
tensor.
=6.08 Hz, 4JH-1,H-3=1.96 Hz, 1H, H-1), 4.60 (dd,

84
K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
Table 5
5.57 Hz, 1H, H-5), 1.48, 1.38 (s, 6H, (CH3)2Cꢀ), 1.15–
0.90 (m, 21H, ꢀSi[CH(CH3)2]3) ppm. 13C-NMR
(125 MHz, CDCl3): l=143.1 (C-1), 105.8 (C-2), 99.5
[(CH3)2Cꢀ], 73.3, 69.7, 67.7, 61.8 (4C, C-3, C-4, C-5,
C-6), 28.9, 18.9 (2C, (CH3)2Cꢀ), 18.0, 17.9 (6C,
ꢀSi[CH(CH3)2]3), 12.2 (3C, ꢀSi[CH(CH3)2]3) ppm. EI-
MS (70 eV): m/z (%)=327.2 (3.6) [M+−CH3], 299.2
(100) [M+−C3H7], 241.1 (97) [M+−C3H7−C3H6O],
197.0 (21) [C10H11], 185.1 (61) [M+−C9H21Si].
Atomic coordinates (×104) and equivalent isotropic displacement
2
3
,
parameters (A ×10 ) for 12a
a
x
y
z
Ueq
Cr1
C1a
O1a
C1b
O1b
C1c
O1c
O1
C2
C3
C4
C4a
C5
3320(1)
1767(2)
834(2)
6066(1)
5600(1)
5295(1)
5196(1)
4642(1)
6471(1)
6741(1)
5329(1)
5353(1)
5577(1)
6394(1)
6479(1)
7117(1)
7674(1)
7196(1)
7890(1)
8588(1)
6635(1)
6671(1)
7045(1)
6016(1)
5521(1)
4738(1)
5941(1)
4565(1)
4576(1)
4789(1)
4199(1)
4900(1)
5519(1)
6646(1)
6836(1)
7171(1)
7934(1)
7207(1)
5953(1)
5450(1)
6107(1)
7618(1)
8054(1)
7363(1)
6137(1)
5703(1)
5416(1)
6629(1)
6930(1)
6717(1)
7055(1)
5869(1)
6375(1)
7025(1)
6978(1)
6362(1)
6262(1)
6717(1)
5694(1)
5657(1)
5413(1)
5206(1)
4587(1)
4014(1)
5277(1)
4758(1)
4878(1)
5840(1)
6431(1)
6949(1)
7567(1)
7830(1)
8008(1)
7520(1)
7529(1)
8309(1)
8310(1)
7955(1)
8988(1)
8817(1)
8594(1)
9558(1)
8506(1)
9143(1)
8480(1)
18(1)
24(1)
35(1)
26(1)
38(1)
26(1)
43(1)
20(1)
19(1)
18(1)
17(1)
17(1)
17(1)
22(1)
18(1)
23(1)
29(1)
19(1)
23(1)
32(1)
19(1)
23(1)
33(1)
18(1)
22(1)
25(1)
24(1)
33(1)
36(1)
20(1)
19(1)
18(1)
23(1)
32(1)
35(1)
25(1)
33(1)
38(1)
25(1)
37(1)
38(1)
3480(2)
3606(2)
1934(2)
1070(2)
6690(1)
7819(2)
7127(2)
6619(2)
5656(2)
4723(2)
4656(1)
3793(2)
2795(2)
3630(2)
3862(2)
2916(2)
3717(2)
4867(2)
5012(1)
4734(3)
5763(2)
8477(2)
9552(1)
8947(2)
7864(2)
10 296(2)
8244(1)
5766(1)
6288(1)
8292(2)
8476(2)
9036(2)
6043(2)
4722(2)
5917(3)
4920(2)
5225(3)
3276(2)
4.4.1.4. Synthesis of stannyl glucals 5 and 6
General procedure. At −78°C 17.5 ml (28.53 mmol)
of tert-butyllithium were added slowly to a solution of
6.19 mmol (3.81 g of 2 or 2.12 g of 4) in 25 ml of THF.
After stirring for 28 min at 0°C, the mixture was cooled
again to −78°C. 5.0 ml (18.47 mmol) of tri-n-butyl-
stannyl chloride were added, the mixture was stirred for
22 min before the reaction was quenched with 100 ml of
water. Extraction of the product with three portions of
Et2O, washing of the combined organic layers with
water and saturated NaCl solution, drying with
MgSO4, evaporation and chromatographic purification
with petroleum ether–CH2Cl2 (8:1) containing 1‰
NEt3 as additive afforded the pure products as colorless
oils (2.97 g, 4.83 mmol, 78% of 5 and 1.89 g, 5.51 mmol,
89% of 6).
O5
C6
C61
C62
C7
C71
C72
C8
O8
C81
C8a
C9
O10
C11
C111
C112
O12
O4
1,5-Anhydro-2-desoxy-3,4,6-O-triisopropylsilyl-1-
(tri-n-butyl-stannyl)-
D
-arabino-hex-1-enitol (5). 1H-
3
NMR (500 MHz, CDCl3): l=4.81 (dd, JH-2,H-3
=
5.07 Hz, 4JH-2,H-4=1.69 Hz, 1H, H-2), 4.10–4.03 (m,
Si4
2
3
2H, H-4, H-5), 3.94 (dd, JH-6,H-6%=10.83 Hz, JH-6,H-5
C41
C411
C412
C42
C421
C422
C43
C431
C432
2
=6.95 Hz, 1H, H-6), 3.89 (dd, JH-6%,H-6%=10.83 Hz,
3JH-6%,H-5=4.97 Hz, 1H, H-6%), 3.83 (pt, JH-3,H-2
=
3
5.07 Hz, 3JHH=2 Hz, 1H, H-3), 1.6–1.4 (m, 6H,
ꢀSn(CH2CH2CH2CH3)3), 1.4–1.2 (6H, ꢀSn(CH2-
CH2CH2CH3)3), 1.0–0.8 (m, 78H, 3 ꢀSi[CH(CH3)2],
ꢀSn(CH2CH2CH2CH3)3) ppm. 13C-NMR (125 MHz,
CDCl3): l=162.3 (C-1), 111.3 (C-2), 80.6 (C-3), 70.2
(C-4), 65.1 (C-5), 62.4 (C-6), 29.0 (3C, ꢀSn(CH2CH2-
CH2CH3)3), 27.3 (3C, ꢀSn(CH2CH2CH2CH3)3), 18.2–
18.0 (18C, ꢀSi[CH(CH3)2]3), 13.7 (3C, ꢀSn(CH2CH2-
CH2CH3)3), 12.6–12.0 (9C, ꢀSi[CH(CH3)2]3), 9.49 (3C,
ꢀSn(CH2CH2CH2CH3)3) ppm. FAB-MS (mNBA): m/z
(%)=903.5 (1.0) [M+−H], 847.5 (5.6) [M+−C4H9],
729.4 (2.2) [M+−C9H21SiOH−H], 687.4 (3.8) [M+−
C9H21SiOH−C3H7], 613.4 (1.3) [M+−SnC12H27−H],
569.4 (3.5) [M+−C3H7−SnC12H27−H], 543.2 (3.4)
[M+−2C9H21SiO−CH3], 397.2 (5.9) [M+−C9H21-
SiO−SnC12H27−C3H7], 291.1 (20) [(SnC12H27)+].
1,5-Anhydro-2-deoxy-4,6-O-isopropylidene-3-O-triiso-
a Ueq is defined as one-third of the trace of the orthogonalized Uij
tensor.
quenched by addition of 100 ml of water. Extraction of
the aqueous layer with CH2Cl2 and purification by
chromatography (petroleum ether–CH2Cl2 1:1) af-
forded 2.42 g (7.06 mmol, 72%) as a colorless oil.
1H-NMR (500 MHz, CDCl3): l=6.23 (dd, JH-1,H-2
3
4
3
=6.16 Hz, JH-1,H-3=1.65 Hz, 1H, H-1), 4.65 (dd, JH-
2,H-1=6.16 Hz, 3JH-2,H-3=1.84 Hz, 1H, H-2), 4.39
3
3
4
(ddd, JH-3,H-4=7.01 Hz, JH-3,H-2=1.84 Hz, JH-3,H-1
=
1.65 Hz, 1H, H-3), 3.90 (dd, 2JH-6e,H-6a=10.81 Hz,
3JH-6e,H-5=5.57, 1H, H-6e), 3.79 (dd, JH-4,H-5=10.43 Hz,
propylsilyl - 1 - (tri - n - butyl - stannyl) - D - arabino - hex - 1-
enitol (6). 1H-NMR (500 MHz, CDCl3): l=4.66 (d,
3JH-4,H-3=7.01 Hz, 1H, H-4), 3.78 (dd, JH-6a,H-6e
=
2
3
3JH-2,H-3=1.89 Hz, 1H, H-2), 4.36 (dd, JH-3,H-4=7.35,
3
10.81 Hz, JH-6a,H-5=10.33 Hz, 1H, H-6a), 3.68 (ddd,
3JH-5,H-4=10.43 Hz, 3JH-5,H-6a=10.33 Hz, JH-5,H-6e
=
3JH-3,H-2=1.89 Hz, 1H, H-3), 3.86 (dd, JH-6e,H-6a
=
3
2

K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
85
10.88 Hz, 3JH-6e,H-5=5.69 Hz, 1H, H-6e), 3.77 (dd,
w(CꢁO)=2064 (m, A11), 1996 (w, B1), 1965. (s, E), 1948
(vs, A21) cm−1
3
3JH-4,H-5=10.44 Hz, JH-4,H-3=7.35 Hz, 1H, H-4), 3.74
.
2
3
(dd, JH-6a,H-6e=10.88 Hz, JH-6a,H-5=10.44 Hz, 1H, H-
3
3
6a), 3.58 (ptd, JH,H=10 Hz, JH-5,H-6e=5.69 Hz, 1H,
H-5), 1.47, 1.37 (s, 6H, (CH3)2Cꢀ), 1.6–0.8 (m, 48H,
ꢀSi[CH(CH3)2]3,
4.4.2.3. Pentacarbonyl[2-desoxy-4,6-O-isopropylidene-
3-O-triisopropylsilyl-D-arabino-hex-1-enopyranosyl-
ꢀSn(C4H9)3)
ppm.
13C-NMR
(methoxy)carbene]chromium (8). 1H-NMR (500 MHz,
(125 MHz, CDCl3): l=162.7 (C-1), 116.5 (C-2), 99.3
((CH3)2Cꢀ), 73.7 (C-3), 70.0 (C-4), 68.6 (C-5), 62.1
(C-6), 29.0, 19.0 (2C, (CH3)2Cꢀ), 28.9, 27.2, 13.7, 9.7,
3
CDCl3): l=5.25 (d, JH-2,H-3=2.35 Hz, 1H, H-2), 4.82
3
3
(s, 3H, CH3Oꢀ), 4.52 (dd, JH-3,H-H-4=7.82 Hz, JH-3,H-2
=2.35 Hz, 1H, H-3), 4.15 (dd, 3JH-6e,H-6a=10.96 Hz,
2JH-6e,H-5=5.09 Hz, 1H, H-6e), 4.03 (m, 1H, H-6a),
(12C,
-ꢀSn(C4H9)3),
17.9,
18.0,
12.3,
(9C,
ꢀSi[CH(CH3)2]3 ppm. FAB-MS (mNBA): m/z (%)=
631.2 (6.3) [M+], 589.1 (8.0) [M+−C3H6], 575.1 (28)
[M+−C3H6O], 531.1 (5.6) [M+−C4H9−C3H7].
3
3
3.86 (ptd, JH,H=10 Hz, JH-5,H-6e=5.47 Hz, 1H, H-5),
3.82 (dd, br, 1H, H-4), 1.50, 1.40 (s, 6H, (CH3)2Cꢀ),
1.2–1.0 (m, 21H, ꢀSi[CH(CH3)2]3) ppm. 13C-NMR
(125 MHz, CDCl3): l=333.8 (CrꢁC), 224.7 (trans-CO),
216.6 (cis-CO), 157.3 (C-1), 102.2 (C-2), 99.7
((CH3)2Cꢀ), 72.2, 70.5, 68.4, 66.8, 61.4 (5C, C-3, C-4,
C-5, C-6, CH3Oꢀ), 28.9, 18.8, (2C, (CH3)2Cꢀ), 18.0,
17.9 (2C, ꢀSi[CH(CH3)2]3), 12.3, (ꢀSi[CH(CH3)2]3)
ppm. EI-MS (70 eV): m/z (%)=576.3 (1.0) [M+], 548.3
(2.8) [M+−CO], 534.2 (B1.0) [M+−C3H6], 464.2
(3.1) [M+−4CO], 436.2 (26) [M+−5CO], 394.2 (8.6)
[M+−C3H6−5CO], 219.9 (72) [M+−C3H6−
4.4.2. Preparation of the carbene complexes 7 and 8
4.4.2.1. General procedure. To a solution of 855 mg
(1.35 mmol) of 6 in 14 ml of THF was added 0.93 ml
(1.48 mmol) of n-BuLi dropwise at −78°C. After stir-
ring for 30 min the solution was combined with a
suspension of 357 mg of Cr(CO)6 (1.62 mmol) in 2 ml
of THF at −78°C. Warming up to −37°C over a
period of 60 min generated the acyl chromate. After
changing the solvent to 40 ml of CH2Cl2, addition of
240 mg of Me3O+BF4−, stirring for 90 min at 0°C and
chromatography with petroleum ether–CH2Cl2 (4:3),
472.8 mg (0.82 mmol, 61%) of 8 were obtained as a red
solid. For the synthesis of complex 7, 3.52 g
(3.89 mmol) of stannyl glucal 5 were applied to the
synthesis of the lithium acyl chromate intermediate.
After stirring for 90 min at −40°C, methylation and
chromatography with petroleum ether–CH2Cl2 (15:1),
2.31 g (2.72 mmol, 70%) of 7 were obtained as a red oil.
C9H21SiOH−5CO−H].
HR-MS:
calc.
for
C25H36CrO10Si 576.1538; found: 576.1478. IR
(petroleum ether): w(CꢁO)=2064 (m, A11), 1994 (w, B1),
1965 (s, E), 1950 (vs, A21) cm−1. Anal. Found: C, 52.27;
H, 6.34. Calc.: C, 57.13; H, 6.29%.
4.4.3. Benzannulation of the glucal carbene complexes
7 and 8
4.4.3.1. General procedure for benzannulation of 7 and 8
with 3-hexyne. A solution of 0.94 mmol (789.3 mg of 7
and 542.0 mg of 8) of the carbene complex and 1.1 ml
(9.4 mmol) of 3-hexyne in 14 ml of tert-butyl methyl
ether was saturated with argon by three pump–freeze–
thaw cycles and warmed under reflux (3.5 h for com-
4.4.2.2. Pentacarbonyl[2-desoxy-3,4,6-tri-O-triisoprop-
ylsilyl-D-arabino-hex-1-enopyranosyl(methoxy)carbene]-
chromium (7). 1H-NMR (500 MHz, CDCl3): l=5.32
(dd, 3JH-2,H-3=5.47 Hz, 4JH-2,H-4=1.49 Hz, 1H, H-2),
3
3
4.77 (s, 3H, CH3O-), 4.55 (ptt, JH-5,H-6=7 Hz, JH-5,H-6%
3
4
plex
7
and 7 h for complex 8). Subsequent
=6.56 Hz, JH-5,H-4=2 Hz, JH-5,H-3=2 Hz, 1H, H-5),
3
3
4
chromatography (petroleum ether–diethyl ether, 8:1,
for the benzannulation of 7 and petroleum ether–di-
ethyl ether, 4:1, for the benzannulation of 8) gave first
the uncoordinated chromans 9b (benzannulation of 7,
168.4 mg, 0.29 mmol, 31%) and 12c (benzannulation of
8, 162.5 mg, 0.31 mmol, 33%) as colorless solids and
then the Cr(CO)3-coordinated chromans 9a (benzannu-
lation of 7, 334.0 mg, 0.37 mmol, 39%), 12a (benzannu-
lation of 8, 207.4 mg, 0.33 mmol, 35%) and 12b
(benzannulation of 8, 66.1 mg, 0.10 mmol, 11%) as
yellow solids.
4.20 (pdd, JH-4,H-3=3 Hz, JH-4,H-5=2 Hz, JH-4,H-2
=
1.49 Hz, 1H, H-4), 4.18 (pdt, 3JH-3,H-2=5.47 Hz,
3JH-3,H-4=3 Hz, 4JH-3,H-5=2 Hz, 1H, H-3), 4.01 (dd,
2JH-6,H-6%=10.63 Hz, JH-6,H-5=7.00 Hz, 1H, H-6), 3.94
3
(dd, 2JH-6%,H-6=10.63 Hz, 3JH-6%,H-5=6.56 Hz, 1H, H-6%),
1.1–0.9 (m, 63H, ꢀSi[CH(CH3)2]3) ppm. 13C-NMR
(125 MHz, CDCl3): l=337.9 (CrꢁC), 225.1 (trans-CO),
216.4 (4C, cis-CO), 156.6 (C-1), 96.9 (C-2), 81.7 (C-3),
68.9 (C-4), 66.8 (C-5), 66.3 (ꢀCH3O), 61.0 (C-6), 18.1–
17.9
(18C,
ꢀSi[CH(CH3)2]3),
12.3–11.9
(3C,
ꢀSi[CH(CH3)2]3) ppm. FAB-MS (mNBA): m/z (%)=
708.4 (100) [M+−5CO], 665.3 (32) [M+−5CO−
C3H7], 621.2 (13) [M+−2C3H7−5CO−H], 535.2 (25)
Tricarbonyl{4a - 8a - p6 - [6,7 - diethyl - 5 - hydroxy - 8-
methoxy-2(R)-triisopropylsilyloxymethyl-3(S),4(R)-bis-
[M+−C9H21SiO−5CO],
307.0
(35)
[M+−
1
(triisopropylsilyloxy)chroman]}chromium (9a). H-NMR
2C9H21SiOH−Cr(CO)5−H]. IR (petroleum ether):
(500 MHz, CD2Cl2): l=4.93 (dd, 3JH-4,H-3=3.28 Hz,

86
K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
3
3
4JH-4,H-2=1.69 Hz, 1H, H-4), 4.81 (s, 1H, OH), 4.47 (m,
3.90 (ptd, JH,H=10 Hz, JH-1,H,-1e=5.76 Hz, 1H, H-2),
3.65 (s, 3H, CH3Oꢀ), 2.74 (m, 1H, ArCH2CH3), 2.53
(m, 1H, ArCH2CH3), 2.44–2.32 (m, 2H, ArCH2CH3),
1.57, 1.45 (s, 6H, (CH3)2Cꢀ), 1.22–1.10 (m, 27H,
3
1H, H-2), 4.42 (dd, 3JH-3,H-4=3.28 Hz, JH-3,H-2
=
1.14 Hz, 1H, H-3), 4.31 (dd, 2JH-1%,H-1=11.23 Hz,
3JH-1,H-2=6.71 Hz,
1H, H-1), 4.26 (dd,
ꢀSi[CH(CH3)2]3,
ArCH2CH3)
ppm.
13C-NMR
2JH-1%,H-1=11.23 Hz, 3JH-1%,H-2=5.86 Hz, 1H, H-1%), 3.77
(s, 3H, ꢀOMe), 2.35–2.89 (m, 4H, ꢀCH2ꢀCH3), 0.90–
1.38 (m, 69H, ꢀCH2CH3, ꢀSiꢀ[CHꢀ(CH3)]3) ppm. 13C-
NMR (125 MHz, CD2Cl2): l=234.8 (3C, Cr(CO)3),
134.9, 133.4, 118.8, 112.5, 90.2, 87.5 (6C, C-4a, C-5,
C-6, C-7, C-8, C-8a), 83.8 (C-2), 67.9 (C-3), 65.5
(ꢀOMe), 64.8 (C-4), 62.6 (C-1), 22.1, 19.8 (2C,
ArCH2CH3), 18.4–17.7 (18C, ꢀSi[CH(CH3)2]3), 16.0,
14.9 (2C, ArCH2CH3), 13.2, 12.6, 12.1 (9C,
ꢀSi[CH(CH3)2]3) ppm. FAB-MS (mNBA): m/z (%)=
902.4 (30) [M+], 859.5 (7.9) [M+−CH3−CO], 818.5
(17) [M+−3CO], 729.3 (4.8) [M+−C9H21SiO], 644.3
(100) [M+−C9H21SiOH−3CO], 601.0 (29) [M+−
(125 MHz, CDCl3): l=234.6 (3C, Cr(CO)3), 136.0,
132.3, 129.0, 128.2, 125.3, 118.5 (6C, C-4a, C-5, C-6,
C-7, C-8, C-8a), 100.4 (1C, (CH3)2Cꢀ), 113.0, 95.7,
81.9, 66.2, 61.0 (5C, C-4, C-3, C-2, C-1‘, CH3Oꢀ), 28.8,
21.7 (2C, (CH3)2Cꢀ), 19.2, 18.5 (2C, ArCH2CH3), 18.3,
18.0 (6C, ꢀSi[CH(CH3)2]3), 16.8, 14.8 (2C, ArCH2CH3),
13.9 (1C, ꢀSi[CH(CH3)2]3) ppm. EI-MS (70 eV): m/z
(%)=630.2 (48) [M+], 615.1 (12) [M+−CH3], 546.2
(13) [M+−3CO], 503.1 (7.5) [M+−C3H7−3CO],
458.2 (73) [M+−CH3−C9H21Si], 445.0 (100) [M+−
C9H21Si−CO], 430.1 (20) [M+−C3H7−C9H21Si],
403.0 (25) [M+−C3H6−C9H21Si−CO], 372.0 (18)
[M+−C9H21SiOH−3CO],
342.0
(66)
[M+−
2C9H21SiO−3CO−H],
C9H21SiOH−Cr(CO)3], 549.3 (4.8) [M+−C3H7−
C9H21SiOH−Cr(CO)3], 471.2 (7.1)
[M+−
2C9H21SiO−3CO−H], 405.3 (55) [M+−CH3−
2C9H21SiO−Cr(CO)3]. IR (petroleum ether):
w(CꢁO)=1960 (vs, A1), 1888 (s, E), 1881 (s, E) cm−1
592.3
(14)
[M+−
C3H6O−C9H21SiOH−2CO], 320.1 (30) [M+−
C9H21SiOH−Cr(CO)3], 284.0 (67) [M+−CH3−
C3H6O2−C9H21SiO−3CO]. HR-MS: Found: 630.2312.
C30H46CrO9Si. Calc.: 630.2316. Anal. Found: C, 57.09;
H, 7.27; C30H46CrO9Si (630.2). Calc.: C, 57.13; H,
7.35%. IR (petroleum ether): n(CꢁO)=1962 (vs, A1),
.
1896 (s, E), 1877 (s, E) cm−1
.
6,7-Diethyl-5-hydroxy-8-methoxy-2(R)-triisopropyl-
silyloxymethyl - 3(S),4(R) - bis(triisopropylsilyloxy)chro-
Minor diastereomer 12b: 1H-NMR (500 MHz,
1
3
man (9b). H-NMR (500 MHz, CD2Cl2): l=5.03 (pq,
CDCl3): l=8.58 (s, ꢀOH), 5.48 (d, JH-4,H-3=8.55 Hz,
4
3
3
3JH-4,H-3=3.13 Hz, JH,H:1.5 Hz, 1H, H-4), 4.72 (m,
H-4), 4.22 (ptd, JH,H=10 Hz, JH,H=6 Hz 1H, H-2),
3.68 (s, CH3Oꢀ), 1.50 (s, 3H, (CH3)2Cꢀ) ppm. 13C-
NMR (125 MHz, CDCl3): l=234.0 (3C, Cr(CO)3)
ppm.
3
1H, ꢀOH), 4.41 (m, 1H, H-3), 4.35 (pq, JH-3,H-4
=
4
2
3.13 Hz, JH,H:1.2 Hz, 1H, H-2), 4.11 (ddd, JH-1,H-1%
3
4
=11.00 Hz, JH-1,H-2=7.65 Hz, JH-1,H-3=1.05 Hz, 1H,
3
H-1), 4.00 (ddd, 2JH-1%,H-1=11.00 Hz, JH-1%,H-2
=
6,7-Diethyl-5-hydroxy-8-methoxy-2(R),3(S)-(buta-3,
3-dimethyl-2,4-O-1,4-diyl)-4(R)-(triisopropylsilyloxy)
4.67 Hz, 4JH-1%,H-3=1.29 Hz, 1H, H-1%), 3.77 (s, 3H,
CH3Oꢀ), 2.48–2.67 (m, 4H, ArCH2CH3), 1.3–0.8 (m,
69H, ꢀSi[CH(CH3)2]3, ArCH2C3) ppm. 13C-NMR
(125 MHz, CD2Cl2): l=148.2, 144.4, 140.4, 135.6,
117.9, 110.3 (6C, C-4a, C-5, C-6, C-7, C-8, C-8a), 82.4
(C-2), 70.0 (C-3), 64.6 (C-4), 64.2 (C-1), 60.7 (ꢀOMe),
20.0, 19.1 (2C, ArCH2CH3), 18.3–17.9 (18C,
ꢀSi[CH(CH3)2]3), 15.7, 14.6 (2C, ArCH2CH3), 12.9,
12.6, 12.2 (9C, ꢀSi[CH(CH3)2]3) ppm. FAB-MS
(mNBA): m/z (%)=766.5 (1.6) [M+], 723.4 (3.5) [M+
−C3H7], 592.3 (39) [M+−C9H21SiOH], 549.3 (9.2)
[M+−C3H7−C9H21SiOH], 523.3 (7.6) [M+−
2C3H7−C9H21Si], 435.2 (4.4) [M+−C9H21Si−
1
chroman (12c). H-NMR (500 MHz, CDCl3): l=7.92
(s, 1H, ꢀOH), 5.26 (d, 3JH-4,H-3=8.30 Hz, 1H, H-4),
4.12 (dd, 3JH-3,H-2=10.13 Hz, 3JH-3,H-4=8.30 Hz, 1H,
H-3), 4.09 (dd, 2JH-1e,H-1a=10.98 Hz, JH-1e,H-2
=
3
3
5.76 Hz, 1H, H-1e), 3.95 (pt, JH,H=10 Hz, 1H, H-1a),
3
3
3.83 (ptd, JH,H=10 Hz, JH-1,H-1e=5.76 Hz, 1H, H-2),
3.70 (s, 3H, CH3Oꢀ), 2.63–2.54 (m, 4H, ArCH2CH3),
1.52, 1.45 (s, 6H, (CH3)2Cꢀ), 1.14–1.08 (27H,
ꢀSi[CH(CH3)2]3,
ArCH2CH3)
ppm.
13C-NMR
(125 MHz, CDCl3): l=150.8, 144.6, 138.7, 137.0,
122.9, 108.3 (6C, C-4a, C-5, C-6, C-7, C-8, C-8a), 99.7
(1C, (CH3)2Cꢀ), 72.7, 72.1, 69.3, 61.6, 61.1 (5C, C-4,
C-3, C-2, C-1%, ꢀOCH3), 29.0, 19.7 (2 C, (CH3)2Cꢀ),
19.1, 18.8 (2C, ArCH2CH3), 18.4, 18.1 (6C,
ꢀSi[CH(CH3)2]3), 15.5, 14.7 (2C, ArCH2CH3), 13.6 (3C,
ꢀSi[CH(CH3)2]3) ppm. EI-MS (70 eV): m/z (%)=494.3
(7.3) [M+], 451.3 (7.5) [M+−C3H6-H], 419.2 (2.3) [M+
−C3H6O2−H], 393.2 (5.7) [M+−C3H7−C3H6O],
337.2 (11) [M+−C9H21Si], 320.2 (100) [M+−
C9H21SiOH], 262.1 (33) [M+−C3H6O−C9H21SiOH].
C9H21SiOH],
419.3
(27)
[M+−C9H21SiO−
C9H21SiOH], 405.3 (100) [M+−CH3−2C9H21SiO].
Tricarbonyl{4a - 8a - p6 - [6,7 - diethyl - 5 - hydroxy - 8-
methoxy-2(R),3(S)-(buta-3,3-dimethyl-2,4-O-1,4-diyl)-
4(R)-(triisopropylsilyloxy)chroman]}chromium (12a,b).
1
Major diastereomer 12a: H-NMR (500 MHz, CDCl3):
l=8.38 (s, 1H, ꢀOH), 5.23 (d, JH-4,H-3=8.79 Hz, 1H,
H-4), 4.49 (dd, JH-3,H-2=9.83 Hz, JH-1,H-4=8.79 Hz,
1H, H-3), 4.04 (dd, JH-1e,H-1a=10.72 Hz, JH-1e,H-2
5.76 Hz, 1H, H-1e), 3.98 (pt, JH,H=10 Hz, 1H, H-1a),
3
3
3
2
3
=
4.4.3.2. General procedure for benzannulation of 7 with
tolan. A solution of 534.7 mg (0.63 mmol) of carbene
3

K.H. Do¨tz et al. / Journal of Organometallic Chemistry 621 (2001) 77–88
87
complex 7 and 1.7 g (1.26 mmol) of tolan was saturated
12.9, 12.5, 12.1 (9C, ꢀSi[C
6
H(CH3)2]3) ppm. IR
(petroleum ether): w(CꢁO)=1984 (vs, A1), 1922 (s, E),
with argon by three pump–freeze–thaw cycles. Warm-
ing under reflux for 2.5 h and chromatographic workup
using petroleum ether–diethyl ether (4:1) gave first 7%
(38.4 mg, 0.045 mmol) of uncoordinated chroman 10b
as a colorless solid and then 46% (285.4 mg, 0.29 mmol)
of chroman complex 10a as a yellow solid. As by-
product, 80.7 mg (0.08 mmol, 13%) of 11 can be ob-
tained as a yellow solid.
1913 (s, E) cm−1
.
6,7 - Diphenyl - 5 - hydroxy - 8 - methoxy - 2(R) - triiso-
propylsilyloxymethyl-3(S),4(R)-bis(triisopropylsilyloxy)-
1
chroman (10b). H-NMR (500 MHz, CD2Cl2): l=7.6–
7.0 (m, 10H, ArꢀH), 5.13 (dd, 3JH-4,H-3=3.43 Hz,
4JH-4,H-2=1.54 Hz, 1H, H-4), 4.90 (s, 1H, OH), 4.52 (m,
1H, H-2), 4.44 (dd, 3JH-3,H-4=3.43 Hz, JH-3,H-2
=
3
Tricarbonyl{4a - 8a - p6 - [6,7 - diphenyl - 6 - hydroxy - 8-
methoxy - 2(R) - triisopropylsilyloxymethyl - 3(S),4(R)-
bis(triisopropylsilyloxy)chroman]}chromium (10a). 1H-
NMR (500 MHz, CD2Cl2): l=7.36–7.0 (m, 10H,
1.29 Hz, 1H, H-3), 4.21 (dd, 2JH-1%,H-1=10.95 Hz,
3JH-1,H-2=7.55 Hz,
1H, H-1), 4.10 (dd,
2JH-1%,H-1=10.95 Hz, 3JH-1%,H-2=4.82 Hz, 1H, H-1%), 3.55
(s, 3H, ꢀOMe), 1.3–0.9 (m, 63H, ꢀSi[CH(CH3)2]3) ppm.
13C-NMR (125 MHz, CD2Cl2): l=147.4, 146.4, 137.3,
135.4, 135.1, 131.6, 131.2, 130.6, 128.8, 127.3, 127.1,
126.2, 118.7, 111.6 (18C, aromatic C), 83.1 (C-2), 69.6
(C-3), 64.3 (C-1), 64.0 (C-4), 60.7 (OMe), 18.3–17.9
(18C, ꢀSi[CH(CH3)2]3), 12.8, 12.5, 12.1 (9C,
ꢀSi[CH(CH3)2]3) ppm. FAB-MS (mNBA): m/z (%)=
863.5 (2) [M+], 819.5 (1.5) [M+−C3H7], 688.3 (15.0)
[M+−C9H21SiOH−H], 645.3 (12) [M+−C3H7−
C9H21SiOH−H], 515.1 (27) [M+−C9H21SiOH], 501.1
(100) [M+−C9H21SiOH−C9H21SiO−C9H21SiOH−
CH3].
3
4
ArꢀH), 5.09 (dd, JH-4,H-3=3,48 Hz, JH-4,H-2=1.79 Hz,
1H, H-4), 4.82 (s, 1H, OH), 4.60 (m, 1H, H-2), 4.54
(dd, 3JH-3,H-4=3.48 Hz, 3JH-3,H-2=1.29 Hz, 1H, H-3),
4.41 (dd, 2JH-1%,H-1=6.36 Hz, 3JH-1,H-2=2.98 Hz, 2H,
H-1, H-1%), 1.4–0.8 (m, 63 H, ꢀSi[CH(CH3)2]3) ppm.
13C-NMR (125 MHz, CD2Cl2): l=234.4 (3C,
Cr(CO)3), 131.8, 131.3, 130.8, 130.6, 129.7, 129.2, 128.9,
127.9, 127.3, 127.2, 126.2, 123.3 (12C, aromatic C-
atoms of phenyl substituents), 134.7, 132.6, 117.1, 93.0,
89.3, 87.3 (6C, C-4a, C-5, C-6, C-7, C-8, C-8a), 84.6
(C-2), 67.8 (C-3), 65.3 (ꢀOMe), 64.6 (C-4), 62.7 (C-1),
18.4–17.7 (18C, ꢀSi[CH(CH3)2]3), 13.2, 12.5, 12.1 (9C,
ꢀSi[CH(CH3)2]3) ppm. FAB-MS (mNBA): m/z (%)=
914.5 (1.5) [M+], 862.5 (3.7) [M+−Cr], 818.5 (1.6)
[M+−Cr−C3H7], 740.3 (2) [M+−C9H21SiOH], 688.3
(14) [M+−C9H21SiOH−Cr], 645.3 (12) [M+−C9H21-
SiOH−Cr−CH3], 515.1 (24) [M+−C9H21SiO−
C9H21SiOH−Cr], 501.1 (100) [M+−2C9H21SiO−
Cr−CH3]. IR (petroleum ether): w(CꢁO)=1961 (vs,
5. Supplementary material
Crystallographic data (excluding structure factors)
for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data
Centre as supplementary publication Nos CCDC-
148674 (8) and CCDC-148675 (12a). Copies of the data
can be obtained free of charge on application to The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk).
A1), 1891 (s, E), 1884 (s, E) cm−1
.
Tricarbonyl{11 - 16 - p6 - [6,7 - diphenyl - 5 - hydroxy - 8-
methoxy-2(R)-triisopropylsilyloxymethyl-3(S),4(R)-bis-
1
(triisopropylsilyloxy)chroman]}chromium (11). H-NMR
(500 MHz, CD2Cl2): l=7.40–6.90 (m, 5H, ArꢀH), 5.51
(pt,
JH,H=6,25 Hz,
4JH-4,H-2=1,79 Hz,
1H,
[Cr(CO)3]ArꢀH), 5.29 (pdt, JH,H=6.59 Hz, JH,H
1.24 Hz, 1H, [Cr(CO)3]ArꢀH), 5.21 (ptd, JH,H
=
=
Acknowledgements
6.46 Hz, JH,H=1.29 Hz, 1H, [Cr(CO)3]ArꢀH), 5.14 (m,
1H, [Cr(CO)3]Arꢀ-H), 5.17 (dd, 3JH-3,H-3=3.33 Hz,
4JH-4,H-2=1.59 Hz, 1H, H-4), 5.06 (ptd, JH,H=6.51 Hz,
Support by the Deutsche Forschungsgemeinschaft
(Graduiertenkolleg Spektroskopie isolierter und kon-
densierter Moleku¨le), the Fonds der Chemischen Indus-
trie and the Ministry of Science and Research (NRW)
is gratefully acknowledged.
J
H,H=1.09 Hz, 1H, [Cr(CO)3]ArꢀH), 4.94 (s, 1H, OH),
4.58 (m, 1H, H-2), 4.47 (dd, 3JH-3,H-4=3.33 Hz, 3JH-3,H-2
2
=1.20 Hz, 1H, H-3), 4.24 (dd, JH-1,H-1%=11.00 Hz,
3JH-1,H-2=5.61 Hz, 1H, H-1), 4.12 (dd, JH-1%,H-1
=
2
11.00 Hz, 3JH-1%,H-2=4.77 Hz, 1H, H-1%), 3.58 (s, 3H,
OMe), 1.4–0.8 (m, 63H, ꢀSi[CH(CH3)2]3) ppm. 13C-
NMR (125 MHz, CD2Cl2): l=231.5 (3C, Cr(CO)3),
147.7, 147.5, 146.4, 137.3, 136.6, 135.8, 131.8, 130.9,
127.7, 126.9, 112.4, 110.6 (12C, aromatic C-atoms
phenyl and chroman), 103.6, 99.7, 98.3, 94.8, 91.3, 90.7,
(6C, aromatic C-atoms of the Cr(CO)3-complexed
phenyl ring), 83.1 (C-2), 69.5 (C-3), 64.1 (2C, C-1,
OMe), 62.7 (C-4), 18.3–17.9 (18C, ꢀSi[CH(CH3)2]3),
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