Directed lithiation in arenetricarbonylchromium(0) complexes: Assessment of some directing group specificities and of electrophilic quench efficacies

Article abstract of DOI:10.1016/S0040-4020(00)00562-7

The synthesis of a series of phenol ethers and 4-triisopropylsilyloxymethylphenol ethers and their η⁶-tricarbonylchromium(0) complexes are reported. The directed lithiation of these followed by quenching with a series of electrophiles gave acce

Full text of DOI:10.1016/S0040-4020(00)00562-7

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 6121±6134
Directed Lithiation in Arenetricarbonylchromium(0) Complexes:
Assessment of Some Directing Group Speci®cities and of
Electrophilic Quench Ef®cacies
a
b
Iyassu K. Sebhat,a Yen-Ling Tan,a David A. Widdowson,a, Rene Wilhelm, Andrew J. P. White
*
Â
and David J. Williamsb
aDepartment of Chemistry, Imperial College of Science Technology and Medicine, London SW7 2AZ, UK
bChemical Crystallography Laboratory, Imperial College of Science Technology and Medicine, London SW7 2AZ, UK
Received 27 March 2000; revised 26 May 2000; accepted 8 June 2000
AbstractÐThe synthesis of a series of phenol ethers and 4-triisopropylsilyloxymethylphenol ethers and their h6-tricarbonylchromium(0)
complexes are reported. The directed lithiation of these followed by quenching with a series of electrophiles gave access to a wide range of
functionalised complexes for use in synthesis. q 2000 Elsevier Science Ltd. All rights reserved.
The chemistry of h6-arenetricarbonylchromium complexes
has been extensively researched and documented.1±5 In
particular, competitive studies of directed lithiation by func-
tional groups on these complexes have established a unique
sequence of directing abilities with ¯uorine as the most
effective of those studied.6 However, the pronounced basi-
city of the lithiated complexes produces limitations in the
range of electrophilic quenches which are synthetically
useful4 and in addition, with the carbon/oxygen based
directing groups, most commonly met with in natural
product and related compound synthesis, the distinction in
directing ability may not be so clear cut.
mium complexes, were conventionally synthesised (89±
98%) (see Experimental for details) from 4-formylphenol
via the alcohols (1±5, series b) which were triisopropyl-
silylated (series c) as shown in Scheme 1. The results are
given in Table 1.
Chromium complexes were made in adequate (45%) to high
(95%) yield by a general procedure,7 Scheme 2, and those
not previously reported are shown in Table 2.
The aryl ether series were: methoxy (6a), previously
examined in detail8 and therefore not listed in the table
but used here for comparison, and (6b), to assess the regio-
selectivity in competition with the 4-silyloxymethyl group;
methoxymethyl (7a,b), to examine the effect of a non-conju-
gated ether oxygen; ethoxymethyl (8a,b), to examine the
effect of increased bulk around that second oxygen; 2-meth-
oxyethyl (9b), to determine the effect of chain length/
ligation ring size; and 2-methoxyethoxymethyl (10b), to
determine the effect of increased potential ligation. One
nitrogen analogue of known high directing ability,9,10
N-Boc-aniline was also produced (11a).
We have therefore addressed the ®rst of these limitations by
examining a range of electrophiles compatible with the high
basicity of the lithiated arenechromium complexes, in the
synthesis of 1,2-difunctionalised arenes. In conjunction with
this, we have probed the relative ef®cacy of the directing
abilities of a number of ether (and one amine) based direct-
ing groups on the aryl rings of the chromium complexed
substrates. The objective was to de®ne optimum arene func-
tionality for application, in chiral form, to the asymmetric
synthesis of biaryls and related natural products to be
reported later.
Lithiations of these complexes were carried out under the
de®ned conditions by treatment with butyllithium at 2788C
in puri®ed THF or ether under a nitrogen atmosphere during
1 h. The resultant lithiated complex was quenched with the
electrophile at 2788C and allowed to warm to room
temperature before work-up (Scheme 3). The results are
given in Table 3. Yields refer to isolated, puri®ed products.
Accordingly, non-commercially available arene ethers (1±5,
series a or c) (Table 1), chosen to probe the effect of the
precise ether structure on directed lithiation in these chro-
Keywords: phenol ether tricarbonylchromium(0) complex; lithiation;
regioselectivity.
* Corresponding author. Tel.: 144-20-7594-5779; fax: 144-20-7594-
5804; e-mail: d.widdowson@ic.ac.uk
The methoxy group in (6b), although a known ortho-direct-
ing group,8 gave a low (5%) but isolable yield of the
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00562-7

6122
I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
Scheme 1.
Table 1. 4-Triisopropylsiloxymethylphenol ether synthesis
No.
R
Yield (%)
a, YˆCHO
b, YˆCH2OH
c, YˆCH2OTIPS
1
2
3
4
5
Me±
MeOCH2±
EtOCH2±
MeOCH2CH2±
MeOCH2CH2OCH2±
96
89
93
97
96
91
96
92
94
98
98
93
98
3-substituted product (12c) in addition to the 2-substituted
product (12b, 87%) on formylation with DMF, despite the
presence of the bulky siloxymethyl group at C-4. Directed
lithiations, including those in these complexes, involve a
combination of the effects of coordination of incoming
base and labilisation of the a-hydrogen by the directing
group11,12 and we have already shown that a methoxy
group is poorly coordinating because of the electron with-
drawal by the chromium unit.13
The other ethers examined here all contain a remote, elec-
tronically detached oxygen three atoms removed from the
aromatic ring, which can act more effectively as a coordi-
nating centre for the lithium base. These all showed
apparently complete regiocontrol and none of the 3-func-
tionalised materials could be isolated, presumably re¯ecting
this coordinating ability. Despite this enhanced regio-
control, isolated yields for 2-formylation of the ethers
methoxymethoxybenzenetricarbonylchromium(7a), ethoxy-
methoxybenzenetricarbonylchromium(0) (8a) and methoxy-
ethoxymethoxybenzenetricarbonylchromium(0) (34a), to
generate (14b, 61%), (29b, 62%) and (34b, 73%) respec-
tively, were less than that for the methoxy analogue (12b,
87%) a possible consequence of the higher steric crowding in
these compounds.
Formylation of the methoxyethoxy analogue to give (32b,
74%) was also accompanied by 18% of the 3-isomer (32c).
Here the poor regiocontrol can reasonably be attributed to
the less favourable coordination ring size of the lithiated
intermediate [7-membered ring for (32b) formation rather
than the 6-membered ring in the methoxymethoxy directed
equivalent (14b), discussed below] resulting in non-selec-
tive lithiation.
The other factor inherent in these substrates is the increased
terminal bulk in the ether side chain [cf. the ethoxymethoxy
series (29a,b), (30a,b) and (31a) with the methoxymethoxy
analogues (14a,b), and (20a,b) and (24a) respectively], had
little signi®cant effect, at least in the cases shown.
The positive effect of the use of the extended coordination
ability of methoxyethoxymethoxy function (34b vs 14b)
may be some signi®cance (110%) in the more crowded b
series and could be of value in dif®cult cases but we have
not made routine use of this more elaborate directing group.
Scheme 2.
The electrophilic quenches were chosen with a number of
objectives in mind. Firstly, the ef®cacy of internal vs
external quench of the lithiated methoxymethoxybenzene-
tricarbonylchromium complexes (7a), (7b) and N-Boc-
anilinetricarbonylchromium (11a)14 was checked using
trimethylsilyl chloride to form (16a,b) and (35a) respec-
tively. In the event, there was no bene®t from an internal
quench and the ®gures for external (post lithiation) are
quoted. Added lithium chloride14 had no discernible effect
on the 77±84% yield.
Table 2. Synthesis of arenetricarbonylchromium(0) complexes
No.
R
Yield (%)
a, YˆH
b, YˆCH2OTIPS
6
7
8
9
10
11
Me±
87
95
93
72
79
MeOCH2±
EtOCH2±
MeOCH2CH2±
78
45
MeOCH2CH2OCH2±
a
The second objective was to introduce functionality which
would be especially valuable in the further synthetic exploi-
tation of the products. These functionalities include formyl
86
a Substituent tBocNH±.

I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
6123
Scheme 3.
Table 3. Directed lithiation of arenetricarbonylchromium(0) complexes
No.
R
Reagent
Z
Yield (%)
b, YˆCH2OTIPS
a, YˆH
12
13
Me±
DMF
Bu3SnCl
OHC±
Bu3Sn±
87a
89
83
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
MeOCH2±
DMF
PhNCO
Me3SiCl
Me3SnCl
Bu3SnCl
(CH2O)n
Ph2CO
(4-MeOC6H4)2CO
PhCHO
4-MeO C6H4CHO
(2,6-MeO)2 C6H3CHO
4-O2N C6H4CHO
Me2N1vCH2I-
PhCHvNPh
ICH2CH2I
OHC±
PhNHCO±
Me3Si±
Me3Sn±
Bu3Sn±
HOCH2±
HO(Ph2)C±
HO(4-MeOC6H4)2C±
HO(Ph)CH±
HO(4-MeOC6H4)CH±
HO[(2,6-MeO)2C6H3]CH±
HO(4-O2NC6H4)CH±
Me2NCH2±
PhNH(Ph)CH±
I±
61
67
80
72
84
95
84
53
94
92
73
83
80
69
72
84
61
95
95
83
29
30
31
EtOCH2±
DMF
Ph2CO
(4-MeOC6H4)2CO
OHC±
HO(Ph2)C±
HO(4-MeOC6H4)2C±
82
82
80
62
92
32
33
34
35
MeOCH2CH2±
DMF
OHC±
74b
72
Ph2CO
DMF
Me3SiCl
HO(Ph2)C±
OHC±
Me3Si±
MeOCH2CH2OCH2±
73
c
77
a 12c, 5% was also formed.
b 32c, 18% was also formed.
t
c Substituent BocNH±.
(12b; 14a,b; 29a,b; 32b and 34b), hydroxymethyl (19a,
20a,b, 21a±25a), aminomethyl (26b), trimethyl and tri-
butylstannyl (17a,b and 13a,18a respectively) and iodide
(28a,b, for use in palladium coupling reactions).15
The third objective was to introduce diastereogenic centres
to probe the stereocontrol of the quench. Thus the aryl-
carbinols of the methoxymethoxy-series (22a±25a) and
the a-aminobenzyl (27a) were produced. In agreement
with earlier observations of butyllithium deprotonations14
these products were formed with high stereoselectivity,
with only one diastereoisomer being isolated in high yield
(69±95%). X-Ray crystallographic analysis of (22a)
showed this to be rel-(1-pR, a-R)-h6-[2-(phenylhydroxy-
methyl)methoxymethoxybenzene]tricarbonylchromium(0)
(Fig. 1).
In summary, we have identi®ed the methoxymethoxy func-
tion as, on balance, the directing group of choice for butyl-
lithium mediated lithiation of aryl ether complexes and have
demonstrated an array of functionalities which can be
Figure 1.

6124
I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
introduced into these systems with the appropriate quench.
The application of these methods to the asymmetric synth-
esis of chiral complexes will be reported in a subsequent
paper.
(ArC(2,6)H), 94.0 (O±CH2±O), 56.2 (OMe). Found: M1
1H, 167.0711. Calcd for C9H11O3: 167.0708.
4-(Ethoxymethoxy)benzaldehyde (3a). Eluent: 50% ether/
hexane; clear colourless oil (96%). (Found: C, 66.74; H,
6.59. C10H12O3 requires: C, 66.65; H, 6.71%). nmax (neat)/
cm21 3070w, 2978s, 2900s, 2739m, 1697vs, 1601s, 1579s,
1508s, 1427m, 1393m, 1314m, 1234s, 1161s, 1110s, 982vs,
835s. dH (270 MHz) 9.85 (1H, s, CHO), 7.79 (2H, d, Jˆ
8.9 Hz, ArC(3,5)H), 7.10 (2H, d, Jˆ8.9 Hz, ArC(2,6)H),
5.26 (2H, s, O±CH2±O), 3.69 (2H, q, Jˆ7.2 Hz, O±CH2),
1.17 (3H, t, Jˆ7.2 Hz, Me); dC (68 MHz) 190.9 (CHO),
162.9 (ArC(1)±O), 131.9 (ArC(3,5)H), 130.6 (ArC(4)±
CHO), 116.3 (ArC(2,6)H), 92.8 (O±CH2±O), 64.8 (O±
CH2), 15.1 (Me). m/z(EI) 180 (M1), 149, 135, 121
(M12OEt). Found: M1 180.0788. Calcd for C10H12O3:
180.0786.
Experimental
Reactions carried out under nitrogen were performed using
standard vacuum line techniques.16 Methoxymethoxy-
benzene was prepared according to a literature procedure.17
4-Hydroxybenzaldehyde and 4-hydroxymethylanisole were
used as received from the Sigma-Aldrich Company. The
concentration of butyllithiums were determined by titration
against diphenylacetic acid.18 Flash column chroma-
tography19 was performed on Sorbisil C-60.
Elemental analyses were carried out at SACS, University of
North London and are reported as the average of two runs,
or by Imperial College Microanalytical Service as one run.
Infrared spectra were recorded on a Perkin±Elmer RX FT-
IR System and a Perkin±Elmer 1710 FTIR instrument.
NMR spectra were performed in CDCl3 at ambient tempera-
ture on a Jeol GSX 270 (270 MHz 1H and 68 MHz 13C) or a
4-(2-Methoxyethoxy)benzaldehyde (4a). But prepared as
previously reported;22 eluent: 50% ether/hexane; clear
colourless oil (92%). (Found: C, 66.90; H, 6.61. Calcd for
C10H12O3: C, 66.65; H, 6.71%). nmax (neat)/cm21 3074w,
3042w, 2930s, 2886s, 2823s, 1747s, 1694vs, 1602s,
1578s, 1509s, 1454s, 1312m, 1260s, 1162s, 1128s,
1057m, 1033m, 834s. dH (270 MHz) 9.82 (1H, s, CHO),
7.77 (2H, d, Jˆ8.9 Hz, ArC(3,5)H), 6.98 (2H, d, Jˆ
8.7 Hz, ArC(2,6)H), 4.16±4.13 (2H, m, O±CH2), 3.74±
3.71 (2H, m, CH2±O), 3.40 (3H, s, OMe); dC (68 MHz)
190.8 (CHO), 163.9 (ArC(1)±O), 132.0 (ArC(3,5)H),
130.1 (ArC(4)±CHO), 114.9 (ArC(2,6)H), 70.7 (CH2±O),
67.7 (O±CH2), 59.3 (OMe). m/z(EI) 180 (M1), 135, 121
(M12MeOC2H4). Found: M1 180.0789. Calcd for
C10H12O3: 180.0786.
1
Bruker DRX 300 (300 MHz H and 75 MHz 13C) Spectro-
meter. Mass spectra were recorded on VG Micromass
7070E or AutoSpec-Q spectrometers. Melting points were
taken on a Ko¯er hot stage apparatus and are uncorrected.
Data are given only for new compounds or compounds
inadequately characterised in the literature.
For both the free ligands and the chromium complexes, the
carbon attached to the directing group has been labelled
ArC(1).
4-[(2-Methoxyethoxy)methoxy]benzaldehyde
(5a).23
Ethoxymethoxybenzene (3, YˆH). This was prepared as
for methoxymethoxybenzene17 in 95% yield. The 1H NMR
spectrum was consistent with the literature data,20 other
data, not earlier reported: nmax (neat)/cm21 2977s, 2900s,
1598s, 1492s. dC (68 MHz) 157.6 (ArC(1)±O), 129.6
(ArC(3,5)H), 121.8 (ArC(4)H), 116.7 (ArC(2,6)H), 92.7
(O±CH2±O), 64.2 (O±CH2), 15.2 (Me). m/z(EI) 152
(M1), 122 (M12C2H4), 107 (M12OCH2CH3).
Eluent: 50% ether/hexane; clear colourless oil (94%).
(Found: C, 62.53; H, 6.77. Calcd for C11H14O4: C, 62.85;
H, 6.71%). nmax (neat)/cm21 2927vs, 1701s, 1601s, 1508s,
1161s, 988s, 843s. dC (68 MHz) 190.8 (CHO), 162.2
(ArC(1)±O), 131.9 (ArC(3,5)H), 130.7 (ArC(4)±CHO),
116.3 (ArC(2,6)H), 93.1 (O±CH2±O), 71.5 (CH2±O), 68.1
(O±CH2), 59.0 (OMe). m/z(CI) 228 (M11NH4), 211
(M11H), 156, 89, 59. Found: M11NH4 228.1240. Calcd
for C11H18NO4: 228.1236.
General procedure for the protection of 4-hydroxy-
benzaldehyde
General procedure for the reduction of the benzal-
dehyde function
To a solution of 4-hydroxybenzaldehyde (18.33 g, 150
mmol) and Adogenw(12 g) in DCM (450 mL), under nitro-
gen, was added a solution of sodium hydroxide (12 g,
300 mmol) in water (150 mL). The appropriate alkyl(chloro-
methyl)ether (225 mmol) was added and the solution left to
stir for 16 h. The organic phase was removed, washed
sequentially with water (150 mL), 1 M HCl aq. (150 mL),
water (150 mL) and brine (150 mL) and dried (MgSO4).
Concentration under reduced pressure followed by ¯ash
chromatography afforded the alkoxymethyl ethers. So
prepared were:-
A solution of the 4-alkoxybenzaldehyde (1a±5a as appro-
priate, 142 mmol) in methanol (280 mL) was stirred at 08C
under nitrogen. Sodium borohydride (8 g, 214 mmol) was
slowly added over a period of 30 min. The solution was
allowed to warm to room temperature and was stirred for
a further 16 h. The methanol was removed in vacuo, water
(250 mL) was added, and the solution acidi®ed to pH 7±8,
saturated with sodium chloride and extracted with ether
(5£100 mL). The combined organic extracts were dried
(Na2SO4) and concentrated under reduced pressure. Column
chromatography afforded the title compounds. So prepared
were:-
4-Methoxymethoxybenzaldehyde (2a). Eluent: 10% ether/
hexane; clear colourless oil (91%); spectrally as reported,21
additionally: dC (75 MHz) 190.7 (CHO), 162.1 (ArC(1)±
O), 131.7 (ArC(3,5)H), 130.6 (ArC(4)±CHO), 116.2
4-Methoxymethoxybenzyl alcohol (2b). Eluent: 50% ethyl
acetate/hexane; distillation gave a clear colourless oil (98%),

I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
6125
bp 1648C @ 2 mmHg (lit.24 1228C @ 2 mmHg) (Found: C,
64.43; H, 7.29. Calcd for C9H12O3: C, 64.27; H, 7.29%).
Spectral data were consistent with the literature.25
69.33; H, 10.27%). nmax (neat)/cm21 2943s, 2866s, 1514s,
1247s, 1095s, 883s, 682s. dH (270 MHz) 7.27 (2H, d,
Jˆ8.9 Hz, ArC(3,5)H), 6.87 (2H, d, Jˆ8.7 Hz,
ArC(2,6)H), 4.77 (2H, s, Ar±CH2), 3.79 (3H, s, OMe),
1.16±1.05 (21H, m, TIPS); dC (68 MHz) 158.6 (ArC(1)±
O), 133.9 (ArC(4)±CH2), 127.2 (ArC(3,5)H), 113.6
(ArC(2,6)H), 64.8 (Ar±CH2), 55.3 (OMe), 18.1 (TIPS±
Me), 12.1 (Si±CH). m/z(CI) 312 (M11NH4), 294 (M1),
293 (M12H), 268, 251, 138, 121. Found: M11NH4
312.2354. C17H34NO2Si requires: 312.2359.
4-Ethoxymethoxybenzyl alcohol (3b). Eluent: 50% ether/
hexane; clear colourless oil (98%). (Found: C, 65.71; H,
7.83. C10H14O3 requires: C, 65.92; H, 7.74%). nmax (neat)/
cm21 3385brs, 3061w, 3035w, 2977s, 2886s, 1612s, 1512s,
1224s, 1172s, 1107s, 1002s, 845s, 818s. dH (270 MHz) 7.24
(2H, d, Jˆ8.7 Hz, ArC(3,5)H), 7.00 (2H, d, Jˆ8.7 Hz,
ArC(2,6)H), 5.18 (2H, s, O±CH2±O), 4.56 (2H, s, Ar±
CH2), 3.69 (2H, q, Jˆ7.2 Hz, O±CH2), 2.14 (1H, s, OH),
1.19 (3H, t, Jˆ7.2 Hz, Me); dC (68 MHz) 156.9 (ArC(1)±
O), 134.3 (ArC(4)±CH2), 128.6 (ArC(3,5)H), 116.3
(ArC(2,6)H), 93.2 (O±CH2±O), 64.9 (Ar±CH2), 64.3 (O±
CH2), 15.2 (Me). m/z(EI) 182 (M1),152, 137, 123, 107, 95,
89, 77, 59. Found: M1 182.0941. C10H14O3 requires:
182.0943.
4-Triisopropylsiloxymethyl(methoxymethoxy)benzene
(2c). Eluent: 10% ether/hexane; colourless oil (89%), bp
1968C. (Found: C, 66.48; H, 9.93. C18H32O3Si requires: C,
66.62; H, 9.94%). nmax (neat)/cm21 2866vs, 1614w, 1511s,
1464m, 817w. dH (270 MHz) 7.29 (2H, d, Jˆ8.7 Hz,
ArC(3,5)H), 7.04 (2H, d, Jˆ8.6 Hz, ArC(2,6)H), 5.19
(2H, s, O±CH2±O), 4.79 (2H, s, Ar±CH2), 3.50 (3H, s,
OMe), 1.2±1.0 (21H, m, TIPS); dC (75 MHz) 156.2
(ArC(1)±O), 135.1 (ArC(4)±CH2), 127.0 (ArC(3,5)H),
116.0 (ArC(2,6)H), 94.5 (O±CH2±O), 64.7 (Ar±CH2),
55.8 (OMe), 18.1 (TIPS±Me), 12.1 (Si±CH). m/z(CI) 281
(M12C3H7), 168 (M12TIPS1H), 151 (M12OTIPS), 136
(1512Me). Found: M11NH4 342.2460. C18H36NO3Si
requires: 342.2464.
4-(2-Methoxyethoxy)benzylalcohol (4b). Eluent: 50%
ether/hexane; clear colourless oil (93%). nmax (neat)/cm21
3405brs, 3063w, 3034w, 2929s, 2878s, 1612s, 1585m,
1512s, 1455m, 1247s, 1127s, 1063m, 925m, 819m. dH
(270 MHz) 7.25±7.18 (2H, m, ArC(3,5)H), 6.87±6.81
(2H, m, ArC(2,6)H), 4.50 (2H, d, Jˆ9.7 Hz, Ar±CH2),
4.07±4.01 (2H, m, O±CH2), 3.72±3.66 (2H, m, CH2O),
3.39 (3H, s, OMe), 2.36 (1H, br s, OH); dC (68 MHz)
158.3 (ArC(1)±O), 133.6 (ArC(4)±CH2), 128.6
(ArC(3,5)H), 114.6 (ArC(2,6)H), 71.1 (CH2±O), 67.3 (O±
CH2), 64.7 (Ar±CH2), 59.2 (OMe). m/z (EI) 182 (M1), 137,
124, 107, 95, 59. Found: M1 182.0937. C10H14O3 requires:
182.0943.
4-Triisopropylsiloxymethyl(ethoxymethoxy)benzene (3c).
Eluent: 10% ether/hexane; colourless liquid (93%). (Found:
C,67.62: H, 10.09. C19H34O3Si requires C, 67.41; H,
10.12%). nmax (neat)/cm21 3063w, 2943vs, 2866s, 1613s,
1587m, 1511s, 1463s, 1375m, 1302m, 1222s, 1171m,
1096vs, 1007s, 919m, 882s. dH (270 MHz) 7.28 (2H, d,
Jˆ8.4 Hz, ArC(3,5)H), 7.02 (2H, d, Jˆ8.7 Hz,
ArC(2,6)H), 5.21 (2H, s, O±CH2±O), 4.78 (2H, s, Ar±
CH2), 3.72 (2H, q, Jˆ6.9 Hz, O±CH2), 1.25 (3H, t,
Jˆ6.9 Hz, Me), 1.34±1.01 (21H, m, TIPS); dC (68 MHz)
156.4 (ArC(1)±O), 135.04 (ArC(4)±CH2), 127.1
(ArC(3,5)H), 116.1 (ArC(2,6)H), 93.3 (O±CH2±O), 64.8
(Ar±CH2), 64.1 (O±CH2), 18.0 (TIPS±Me), 15.0 (Me),
11.9 (Si±CH). m/z(CI) 338 (M1), 337 (M12H), 312, 295,
265, 176, 165. Found: M1 338.2247. C19H34O3Si requires:
338.2277
4-(2-Methoxyethoxy)methoxybenzyl alcohol (5b). Eluent:
50% ether/hexane; clear colourless oil (98%). (Found: C,
62.37; H, 7.73. C11H16O4 requires: C, 62.25; H, 7.60%). nmax
(neat)/cm21 3428br, 2927m, 2882m, 1613m, 1511s, 1223s,
1104s, 1006s, 847m. dH (270 MHz) 7.23 (2H, d, Jˆ6.7 Hz,
ArC(3,5)H), 7.00 (2H, d, Jˆ8.7 Hz, ArC(2,6)H), 5.22 (2H,
s, O±CH2±O), 4.56 (2H, s, Ar±CH2), 3.78 (2H, t, Jˆ4.4 Hz,
O±CH2), 3.52 (2H, t, Jˆ4.7 Hz, CH2±O), 3.33 (3H, s,
OMe), 1.24 (1H, s, OH); dC (68 MHz) 156.8 (ArC(1)±O),
134.5 (ArC(4)±CH2), 128.6 (ArC(3,5)H), 116.4
(ArC(2,6)H), 93.5 (O±CH2±O), 71.8 (CH2±O), 67.6 (O±
CH2), 64.9 (Ar±CH2), 59.1 (OMe). m/z(EI) 212 (M1), 195
(M12OH), 137, 107, 89, 59. Found: M1 212.1055.
C11H16O4 requires: 212.1049.
4-Triisopropylsiloxymethyl(2-methoxyethoxy)benzene
(4c). Eluent: 10% ether/hexane; colourless liquid (97%).
(Found: C, 67.64; H, 10.28. C19H34O3Si requires: C,
67.41; H, 10.12%). nmax (neat)/cm21 3064w, 3033w,
2942s, 2866s, 2725w, 1613m, 1586w, 1512s, 1463s,
1374m, 1247s, 1129m, 1095m, 1066m, 1012m, 923m,
882s, 807s. dH (270 MHz) 7.25 (2H, d, Jˆ8.7 Hz,
ArC(3,5)H), 6.88 (2H, d, Jˆ8.7 Hz, ArC(2,6)H), 4.75
(2H, s, Ar±CH2), 4.08 (2H, t, Jˆ4.7 Hz, O±CH2), 3.73
(2H, t, Jˆ4.7 Hz, CH2±O), 3.43 (3H, s, OMe), 1.12±0.96
(21H, m, TIPS); dC (68 MHz) 157.8 (ArC(1)±O), 134.3
(ArC(4)±CH2), 127.1 (ArC(3,5)H), 114.3 (ArC(2,6)H),
71.2 (CH2±O), 67.3 (O±CH2), 64.8 (Ar±CH2), 59.3
(OMe), 18.1 (TIPS±Me), 12.1 (Si±CH). m/z(CI) 356
(M11NH4), 338 (M1), 337 (M12H), 312, 192, 165, 148,
120. Found: M11NH4 356.2612. C19H38NO3Si requires:
356.2621.
General procedure for triisopropylsilyl(TIPS)
protection26
A solution of the 4-alkoxybenzyl alcohol (1b±5b as appro-
priate, 137 mmol), imidazole (28 g, 412 mmol) and triiso-
propylsilyl chloride (35.3 mL, 165 mmol) in DMF
(150 mL) was stirred at r.t. for 16 h. Ether (300 mL) was
added, extracted with water (5£100 mL) and dried
(MgSO4). Concentration under reduced pressure followed
by ¯ash chromatography furnished the title compounds.
So prepared were:
4-Triisopropylsiloxymethyl(methoxy)benzene
(1c).
4-Triisopropylsiloxymethyl(2-methoxyethoxymethoxy)-
benzene (5c). Eluent: 30% ether/hexane; colourless liquid
Eluent: 10% ether/hexane; colourless liquid (96%).
(Found: C, 69.19; H, 10.17. C17H30O2Si requires: C,

6126
I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
(96%). (Found: C, 64.96; H, 10.11. C20H36O4Si requires: C,
65.17; H, 9.84%). nmax (neat)/cm21 2943s, 2867s, 1511s,
1464m, 1221m, 1097s, 883m, 681m. dH (270 MHz) 7.25
(2H, d, Jˆ8.7 Hz, ArC(3,5)H), 7.00 (2H, d, Jˆ8.7 Hz,
ArC(2,6)H), 5.25 (2H, s, O±CH2±O), 4.76 (2H, s, Ar±
CH2), 3.80 (2H, t, Jˆ4.0 Hz, O±CH2), 3.54 (2H, t,
Jˆ4.0 Hz, CH2±O), 3.36 (3H, s, OMe), 1.19±0.95 (21H,
m, TIPS); dC (68 MHz) 156.2 (ArC(1)±O), 135.2
(ArC(4)±CH2), 127.9 (ArC(3,5)H), 116.1 (ArC(2,6)H),
93.7 (O±CH2±O), 71.6 (CH2±O), 67.6 (O±CH2), 64.7
(Ar±CH2), 59.1 (OMe), 18.1 (TIPS±Me), 12.3 (Si±CH).
m/z(CI) 386 (M11NH4), 368 (M1), 367 (M12H), 325,
195, 59. Found: M11NH4 386.2714. C20H40NO4Si requires:
386.2727.
(2H, s, O±CH2±O), 4.89 (1H, t, Jˆ6.2 Hz, ArC(4)H),
3.49 (3H, s, OMe); dC (75 MHz) 140.6 (ArC(1)±O), 95.3
(O±CH2±O), 94.6 (ArC(3,5)H), 86.1 (ArC(4)H), 80.6
(ArC(2,6)H), 56.93 (OMe). m/z(EI) 274 (M1), 218
(M122£CO), 190 (M123£CO), 175 (1902Me), 158
(M12MeOH), 145 (1902CH2OMe). Found: M1
273.9938. C11H10CrO5 requires 273.9933.
h6-[4-Triisopropylsiloxymethyl(methoxymethoxy)ben-
zene]tricarbonyl-chromium(0) (7b). This complex was
prepared from 4-triisopropyloxymethyl(methoxymethoxy)-
benzene (2c, 10.0 g, 318 mmol) and chromium hexacarbo-
nyl (13.2 g, 60 mmol), re¯uxed for 48 h in dibutyl ether:
THF (300 mL:20 mL). FCC (eluent: 10% ether/hexane)
furnished the complex (7b) as a bright yellow crystalline
solid. (13.50 g, 28.5 mmol, 95%), mp 32±348C. (Found:
C, 54.76; H, 7.19. C21H32CrO6Si requires: C, 54.77; H,
7.00%). nmax (neat)/cm21 2944s, 1887brs, 1880brs. dH
(270 MHz) 5.60 (2H, d, Jˆ7.2 Hz, ArC(3,5)H), 5.32 (2H,
d, Jˆ6.9 Hz, ArC(2,6)H), 5.03 (2H, s, O±CH2±O), 4.42
(2H, s, Ar±CH2±O), 3.48 (3H, s, OMe), 1.2±1.0 (21H, m,
TIPS); dC (75 MHz) 139.9 (ArC(1)±O), 105.5 (ArC(4)±
CH2), 95.4 (O±CH2±O), 92.7 (ArC(3,5)H), 80.2
(ArC(2,6)H), 63.0 (Ar±CH2), 56.8 (OMe), 18.0 (TIPS±
Me), 11.9 (Si±CH). m/z(CI) 478 (M11NH4), 461
(M11H), 287 (M12OTIPS), 121 (2872Cr(CO)3).
Found: M11NH4 478.1723. C21H36CrNO6Si requires:
478.1717.
General procedure for the preparation of arenetricar-
bonylchromium(0) complexes
A mixture of the arene indicated (1.0 equiv.) and chromium
hexacarbonyl (0.2±2 equiv.) in a deoxygenated ethereal
solvent (dibutyl ether/THF or dioxane) was attached to a
wide-bore air condenser or Strohmeier apparatus in line
with a water condenser and heated under re¯ux for 12±
48 h under a positive pressure of nitrogen and in subdued
light. The resulting yellow/orange solution was cooled,
®ltered through a short pad of Celite, eluted with ether
and concentrated under reduced pressure. Flash column
chromatography (FCC) and/or recrystallisation as appro-
priate furnished the desired complex. So prepared were:-
h6-(Ethoxymethoxybenzene)tricarbonylchromium(0) (8a).
This complex was prepared from ethoxymethoxy-benzene
(3, YˆH, 8.0 g, 52.6 mmol) and chromium hexacarbonyl
(17.35 g, 78.8 mmol), re¯uxed for 36 h in dibutyl ether:
THF (300 mL: 30 mL). FCC (eluent: 10% ether/hexane)
gave the complex (8a) as bright yellow crystals (6.85 g,
23.8 mmol, 45%), mp 74±768C. (Found: C, 50.17; H, 4.31
C12H12CrO5 requires: C, 50.01; H, 4.20%). nmax (CHCl3)/
cm21 1969vs, 1890vs. dH (270 MHz) 5.50 (2H, t, Jˆ6.5 Hz,
ArC(3,5)H), 5.30 (2H, d, Jˆ6.5 Hz, ArC(2,6)H), 5.08 (2H,
s, O±CH2±O), 4.89 (1H, t, Jˆ6.5 Hz, ArC(4)H), 3.72 (2H,
q, Jˆ7.1 Hz, O±CH2), 1.23 (3H, t, Jˆ7.1 Hz, Me); dC
(68 MHz) 233.2 (CO), 141.0 (ArC(1)±O), 94.7 (O±CH2±
O), 93.9 (ArC(3,5)H), 86.1 (ArC(4)H), 80.7 (ArC(2,6)H),
65.2 (O±CH2), 15.0 (Me). m/z(CI) 306 (M11NH4), 289
(M11H), 221, 177, 86, 52. Found (CI): M11H 289.0163.
C12H13CrO5 requires 289.0168.
h6-[4-Triisopropylsiloxymethyl(methoxy)benzene]tricar-
bonylchromium(0) (6b). This complex was prepared from
4-triisopropylsiloxymethyl(methoxy)benzene (1c, 10.0 g,
34 mmol) and chromium hexacarbonyl (11.22 g,
51.00 mmol), re¯uxed for 48 h. in dibutyl ether: THF
(300 mL: 30 mL). FCC (eluent: 15% ether/hexane) to
furnish the complex (6b) as a bright yellow crystalline
solid. (12.73 g, 29.58 mmol, 87%), mp 52±548C. (Found:
C, 55.69; H, 7.00. C20H30CrO5Si requires: C, 55.80; H,
7.02%). nmax (KBr)/cm21 2943s, 2864s, 1957vs, 1877vs,
1848vs, 1544m, 1255s, 1105m, 804m, 626s. dH
(270 MHz) 5.63 (2H, d, Jˆ6.9 Hz, ArC(3,5)H), 5.11 (2H,
d, Jˆ6.9 Hz, ArC(2,6)H), 4.41 (2H, s, Ar±CH2), 3.68 (3H,
s, OMe), 1.17±1.03 (21H, m, TIPS±Me); dC (68 MHz)
233.3 (CO), 142.7 (ArC(1)±O), 104.7 (ArC(4)±CH2), 93.2
(ArC(3,5)H), 77.6 (ArC(2,6)H), 63.1 (Ar±CH2), 55.7
(OMe), 18.0 (TIPS±Me), 12.0 (Si±CH). m/z(CI) 448
(M11NH4), 431 (M11H), 363 (4482H23£CO), 346
(M123£CO), 312 (4482Cr(CO)3), 294 (M12Cr(CO)3),
257 (M12TIPSO), 138, 121, 52. Found: M1 430.1262.
C20H30CrO5Si requires: 430.1268.
h6-[4-Triisopropylsiloxymethyl(ethoxymethoxy)benzene]-
tricarbonyl-chromium(0) (8b). This complex was
prepared from 4-triisopropylsiloxymethyl(ethoxymethoxy)-
benzene (3c, 10.0 g, 30 mmol) and chromium hexacarbonyl
(13 g, 57 mmol), re¯uxed for 48 h. in dibutyl ether: THF
(300 mL:30 mL). FCC (eluent: 10% ether/hexane) furn-
ished the complex (8b) as a bright yellow crystalline solid.
(13.4 g, 28.2 mmol, 93%), mp 52±538C. (Found: C, 55.88;
H, 7.45. C22H34CrO6Si requires: C, 55.68; H, 7.22%). nmax
(KBr)/cm21 3098w, 2943s, 2865s, 1968vs, 1866vs, 1541m,
1486m, 1228s, 1064s, 970s, 800m, 680m, 630s, 532m. dH
(270 MHz) 5.69 (2H, d, Jˆ7.2 Hz, ArC(3,5)H), 5.32 (2H, d,
Jˆ7.2 Hz, ArC(2,6)H), 5.06 (2H, s, O±CH2±O), 4.42 (2H,
s, Ar±CH2±O), 3.70 (2H, q, Jˆ7.2 Hz, O±CH2), 1.23 (3H, t,
Jˆ7.2 Hz, Me), 1.17±0.98 (21H, m, TIPS); dC (68 MHz)
233.3 (CO), 140.1 (ArC(1)±O), 105.4 (ArC(4)±CH2), 94.1
h6-(Methoxymethoxybenzene)tricarbonylchromium(0)
(7a). This complex was prepared from methoxymethoxy-
benzene (2, YˆH, 2.20 g, 20.0 mmol) and chromium hexa-
carbonyl (5.50 g, 25.0 mmol), re¯uxed for 8 h in dioxane
(120 mL). FCC (eluent: 10% ether/hexane) and recrystalli-
sation (from DCM/hexane), furnished the complex (7a) as
bright yellow crystals (4.28 g, 15.6 mmol, 78%), mp 71±
728C. (Found: C, 47.93; H, 3.64. C11H10CrO5 requires: C,
48.19; H, 3.68%). nmax (Nujol)/cm21 3019m, 1970s, 1892s,
1215vs, 757s. dH (270 MHz) 5.51 (2H, t, Jˆ6.4 Hz,
ArC(3,5)H), 5.29 (2H, d, Jˆ6.4 Hz, ArC(2,6)H), 5.05

I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
6127
(O±CH2±O), 92.8 (ArC(3,5)H), 80.2 (ArC(2,6)H), 65.2
(Ar±CH2), 63.1 (O±CH2), 18.0 (TIPS±Me), 15.0 (Me),
11.9 (Si±CH). m/z(EI) 474 (M1), 390 (M123£CO), 348,
318, 295, 289, 159, 52. Found: M1 474.1552. C22H34CrO6Si
requires: 474.1529.
151.9 (COO), 119.2 (ArC(1)±N), 94.6 (ArC(3,5)H), 92.7
(ArC(4)H), 86.4 (ArC(2,6)H), 82.3 (O±CMe3), 28.14
(Me). m/z(CI) 347 (M11NH4), 291 (34722£CO), 274
(M122£CO1H),
(2302Cr(CO)3).
C14H19CrN2O5 requires 347.0699.
230
(3472NH2CO2 Bu),
94
347.0708.
t
Found:
M11NH4
h6-[4-Triisopropylsiloxymethyl(2-methoxyethoxy)ben-
zene]tricarbonylchromium(0) (9b). This complex was
prepared from 4-triisopropylsiloxymethyl(2-methoxy-
ethoxy)benzene (4c, 10.0 g, 30 mmol) and chromium hexa-
carbonyl (13 g, 57 mmol), re¯uxed for 48 h in dibutyl ether:
THF (300 mL: 30 mL). FCC (eluent: 10% ether/hexane)
furnished the complex (9b) as a bright yellow crystalline
solid. (9.9 g, 21.7 mmol, 72%), mp 30±318C. (Found: C,
55.91; H, 7.18. C22H34CrO6Si requires: C, 55.68; H,
7.22%). nmax (KBr)/cm21 3108w, 3078w, 2941s, 2865s,
1966vs, 1884vs, 1548m, 1450s, 1254s, 1129s, 1087s,
882m, 805m, 677s, 685s, 536m. dH (270 MHz) 5.60 (2H,
d, Jˆ6.7 Hz, ArC(3,5)H), 5.13 (2H, d, Jˆ6.7 Hz,
ArC(2,6)H), 4.38 (2H, s, Ar±CH2), 3.94 (2H, s, O±CH2),
3.63 (2H, s, CH2±O), 3.36 (3H, s, OMe), 1.17±0.98 (21H,
m, TIPS); dC (68 MHz) 233.3 (CO), 141.9 (ArC(1)±O),
104.9 (ArC(4)±CH2), 93.2 (ArC(3,5)H), 78.3 (ArC(2,6)H),
70.4 (CH2±O), 68.1 (O±CH2), 63.1 (Ar±CH2), 59.1 (OMe),
18.0 (TIPS±Me), 11.9 (Si±CH). m/z(CI) 492 (M11NH4),
475 (M11H), 391 (M11H23£CO), 347, 312, 301, 268,
184, 165. Found: M1 474.1534. C22H34CrO6Si requires:
474.1529.
General procedure for the regiocontrolled deproton-
ation of arenetricarbonylchromium(0) complexes
Butyllithium (1.1 equiv.) was added to a solution of the
complex indicated (1 equiv.) in deoxygenated THF
(15 mL) or diethyl ether (20 mL) at 2788C, under nitrogen.
The resultant solution was allowed to stir for a further 1 h,
then quenched with a suitable electrophile (0.9±5 equiv.)
and allowed to warm slowly to room temperature over a
period of 3±15 h. The THF was removed in vacuo and
replaced with ether (20 mL). Unless otherwise stated, the
reaction was worked up with 1 M HCl aq. (5 mL), and the
organic phase was washed with water (2£20 mL) and brine
(20 mL), dried (MgSO4) and concentrated under reduced
pressure. FCC and/or recrystallisation as appropriate furn-
ished the desired functionalised complex. So prepared
were:-
(^)-h6-[2-Formyl-4-triisopropylsiloxymethyl(methoxy)-
benzene]tricarbonylchromium(0) (12b). This complex
was prepared from h6-[4-triisopropylsiloxymethyl(meth-
oxy)benzene]tricarbonylchromium(0) (6b, 280 mg, 0.65
mmol) with a DMF quench (0.10 mL, 1.30 mmol). FCC
(eluent: 30% ether/hexane). The ®rst eluted compound
was the 3-substituted complex (12c) as an orange crystalline
solid (15 mg, 0.03 mmol, 5%) mp 46±488C. (Found: C,
55.13; H, 6.78%. C21H30CrO6Si requires: C, 55.01; H,
6.59%). nmax (KBr)/cm21 2944m, 2866m, 1973vs, 1902vs,
1886vs, 1681s, 1542m, 1276m, 1116m, 1015m, 655s, dH
(270 MHz) 9.83 (1H, s, CHO), 5.74 (1H, d, Jˆ6.9 Hz,
ArC(5)H), 5.99 (1H, d, Jˆ2.2 Hz, ArC(2)H), 5.51 (1H,
dd, Jˆ2.2 Hz 6.9 Hz, ArC(6)H), 4.95 (1H, d, Jˆ13.9 Hz,
Ar±CH2), 4.73 (1H, d, Jˆ13.9 Hz, Ar±CH2), 3.71 (3H, s,
OMe), 1.22±1.00 (21H, m, TIPS); dC (68 MHz) 231.4 (CO),
189.5 (CHO), 139.6 (ArC(1)±O), 108.9 (ArC(4)±CH2),
93.6 (ArC(3)±CHO), 91.0 (ArC(2)H), 81.5 (ArC(5)H),
77.9 (ArC(6)H), 61.3 (C, Ar±CH2), 56.4 (C, OMe), 18.0
(TIPS±Me), 11.9 (Si±CH). m/z (FAB1) 458 (M1), 374
(M123£CO), 337, 285, 149, 136. Found: M1, 458.1220.
C27H30CrO6Si requires: 458.1217.
h6-[4-Triisopropylsiloxymethyl(2-methoxyethoxymethoxy)-
benzene]tricarbonylchromium(0) (10b). This complex
was prepared from 4-triisopropylsiloxymethyl(2-methoxy-
ethoxymethoxy)benzene (5c, 6.00 g, 16.30 mmol) and chro-
mium hexacarbonyl (7.17 g, 32 mmol), re¯uxed for 48 h in
dibutyl ether: THF (300 mL: 30 mL). FCC (eluent: 20%
ether/hexane) furnished the complex (10b) as a bright
yellow crystalline solid. (6.53 g, 12.87 mmol, 79%), mp
12±148C. (Found: C, 54.75; H, 7.03. C23H36CrO7Si
requires: C, 54.75; H, 7.19%). nmax (neat)/cm21 2944s,
2867s, 1988vs, 1883vs, 1485m, 1462m, 1227s, 1109s,
629s. dH (270 MHz) 5.59 (2H, d, Jˆ6.9 Hz, ArC(3,5)H),
5.34 (2H, d, Jˆ6.9 Hz, ArC(2,6)H), 5.11 (2H, s, O±CH2±
O), 4.41 (2H, s, Ar±CH2), 3.81 (2H, t, Jˆ4.2 Hz, O±CH2),
3.57 (2H, t, Jˆ4.2 Hz, CH2±O), 3.37 (3H, s, OMe), 1.18±
0.93 (21H, m, TIPS); dC (68 MHz) 233.3 (CO), 139.9
(ArC(1)±O), 105.6 (ArC(4)±CH2), 94.3 (O±CH2±O), 92.7
(ArC(3,5)H), 80.3 (ArC(2,6)H), 71.4 (CH2±O), 68.5 (O±
CH2), 63.1 (Ar±CH2), 59.2 (OMe), 18.1 (TIPS±Me), 12.3
(Si±CH). m/z(CI) 522 (M11NH4), 386 (5222Cr(CO)3),
192, 148, 52 (Cr). Found: M11NH4 522.1982.
C23H40CrNO7Si requires: 522.1979.
Further elution gave the complex (12b), as a bright orange
crystalline solid (2 equiv., 261 mg, 0.57 mmol, 87%) mp
79±818C. (Found: C, 55.15; H, 6.37. C21H30CrO6Si
requires: C, 55.01; H, 6.59%). nmax (KBr)/cm21 2942m,
2865m, 1965vs, 1884vs, 1670s, 1144m, 662s. dH
(270 MHz) 10.03 (1H, s, CHO), 6.29 (1H, d, Jˆ1.7 Hz,
ArC(3)H), 5.99 (1H, dd, Jˆ1.7, 7.2 Hz, ArC(5)H), 5.04
(1H, d, Jˆ7.2 Hz, ArC(6)H), 4.48 (1H, d, Jˆ12.6 Hz, Ar±
CH2), 4.42 (1H, d, Jˆ12.6 Hz, Ar±CH2), 3.83 (3H, s, OMe),
1.12±0.81 (21H, m, TIPS); dC (68 MHz) 230.7 (CO), 185.6
(CHO), 142.3 (ArC(1)±O), 104.3 (ArC(4)±CH2), 93.1
(ArC(3)H), 90.4 (ArC(5)H), 85.2 (ArC(2)±CHO), 71.5
(ArC(6)H), 62.8 (Ar±CH2), 56.2 (OMe), 18.0 (TIPS±Me),
11.9 (Si±CH). m/z(EI) 458 (M1), 374 (M123£CO), 331,
h6-(N-t-Butoxycarbonylaniline)tricarbonylchromium(0)
(11a). This complex was prepared from N-t-butoxycarbo-
nylaniline (5.80 g, 30.0 mmol) and chromium hexacarbonyl
(7.33 g, 30.0 mmol), re¯uxed for 48 h in dioxane (150 mL).
FCC (eluent: 2±5% ether/hexane) and recrystallisation
(from DCM/hexane) furnished the complex (11a) as bright
yellow crystals (8.49 g, 25.8 mmol, 86%), mp 121±1228C.
nmax (Nujol)/cm21 3300m, 2925vs, 1955s, 1892, 1855,
1716, 1463s, 675m, 631m. dH (270 MHz) 6.01 (1H, s,
NH), 5.62±5.51 (4H, m, ArC(2,3,5,6)H), 4.92 (1H, t,
t
Jˆ6.0 Hz, ArC(4)H), 1.49 (9H, s, Bu); dC (75 MHz)

6128
I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
288, 257, 217, 170, 147, 52. Found: M1 458.1211.
C21H30CrO6Si requires: 458.1217.
m, TIPS); dC (68 MHz) 230.8 (CO), 185.6 (CHO), 141.1
(ArC(1)±O), 104.1 (ArC(4)±CH2), 95.7 (O±CH2±O), 93.4
(ArC(3)H), 89.9 (ArC(5)H), 85.3 (ArC(2)±CHO), 75.5
(ArC(6)H), 62.7 (Ar±CH2), 57.5 (OMe), 18.0 (TIPS±Me),
11.9 (Si±CH). m/z(CI) 506 (M11NH4), 489 (M11H), 370
(5062Cr(CO)3). Found: M11H 489.1399. C22H33CrO7Si
requires: 489.1401.
(^)-h6-(2-Tributylstannylanisole)tricarbonylchromium(0)
(13a). This complex was prepared from h6-(anisole)tri-
carbonylchromium(0) (6a, 0.24 g, 1.00 mmol) with a tri-
butyltin chloride (1.4 equiv., 0.40 mL, 1.40 mmol) quench.
The reaction was worked up with saturated aqueous KF
(10 mL). FCC (eluent: 5% ether/hexane) furnished the
complex (13a) as a yellow oil (0.47 g, 0.89 mmol, 89%).
nmax (Nujol)/cm21 2956s, 1958vs, 1881vs, 1452s. dH
(270 MHz) 5.61 (1H, ddd, Jˆ1.5, 6.2, 6.9 Hz, ArC(5)H),
5.50 (1H, dd, Jˆ1.5, 5.9 Hz, ArC(3)H), 5.01 (1H, d, Jˆ
6.9 Hz, ArC(6)H), 4.84 (1H, dt, Jˆ0.5, 6.1 Hz, ArC(4)H),
3.68 (3H, s, OMe), 1.70±1.48 (6H, m, CH2CH3), 1.45±1.20
(6H, m, SnCH2CH2), 1.10 (6H, t, Jˆ9.4 Hz, SnCH2), 0.90
(9H, t, Jˆ7.4 Hz, CH2CH3); dC (75 MHz) 146.6 (ArC(1)±
O), 103.1 (ArC(3)H), 95.4 (ArC(4)H), 89.6 (ArC(2)±Sn),
86.8 (ArC(5)H), 74.4 (ArC(6)H), 55.3 (OMe), 28.9
(SnCH2CH2), 27.8 (CH2CH3), 13.6 (SnCH2), 10.7
(CH2CH3). m/z(CI) 534 (M11H), 477 (M122£CO), 291
(Bu3SnH). Found: M1 533.0964. C22H35CrO4Sn requires:
533.0957.
(^)-h6-[2-(N-Phenylcarboxamido)-4-triisopropylsiloxy-
methyl(methoxymethoxy)benzene]tricarbonylchromium(0)
(15b). This complex was prepared from h6-[4-triisopropyl-
siloxy-methyl(methoxy-methoxy)benzene]tricarbonylchro-
mium(0) (7b, 300 mg, 0.65 mmol) in ether (20 mL) with a
quench of phenyl isocyanate (0.35 mL, 3.24 mmol). The
reaction was worked up with water (10 mL). FCC (eluent:
30% ether/hexane) furnished the complex (15b) as a bright
orange crystalline solid (252 mg, 0.44 mmol, 67%) mp 58±
608C. nmax (KBr)/cm21 3356w, 3090w, 2945m, 2867m,
1962vs, 1896vs, 1877vs, 1671s, 1600m, 1557s, 1443s,
1187m, 1071m, 913m, 659s, 530m. dH (270 MHz) 9.12
(1H, NH), 7.52±7.23 (5H, m, PhH), 6.6 (1H, d, Jˆ1.7 Hz,
ArC(3)H), 5.87 (1H, dd, Jˆ1.7, 6.9 Hz, ArC(5)H), 5.42
(1H, d, Jˆ6.9 Hz, ArC(6)H), 5.34 (1H, d, Jˆ6.7 Hz, O±
CHH±O), 5.23 (1H, d, Jˆ6.7 Hz, O±CHH±O), 4.53 (1H,
d, Jˆ12.6 Hz, Ar±CH2), 4.43 (1H, d, Jˆ12.6 Hz, Ar±CH2),
3.59 (3H, s, OMe), 1.13±0.98 (21H, m, TIPS); dC (68 MHz)
231.4 (CO), 161.1 (CON), 138.2 (ArC(1)±O), 137.4±127.2
(Ph(C)H), 104.8 (ArC(4)±CH2), 96.7 (ArC(3)H), 94.0 (O±
CH2±O), 93.2 (ArC(5)H), 85.4 (ArC(2)±CON), 76.5
(ArC(6)H), 62.8 (Ar±CH2), 57.7 (OMe), 18.1 (TIPS±Me),
11.9 (Si±CH). m/z(CI) 597 (M11NH4), 580 (M11H), 444
(5802Cr(CO)3). Found: M11H: 580.1812. C28H38CrO7SiN
requires: 580.1823.
(^)-h6-[2-Formyl(methoxymethoxy)benzene]tricarbonyl-
chromium(0) (14a). This complex was prepared from
h6-(methoxymethoxybenzene)tricarbonylchromium(0) (7a,
0.350 g, 1.28 mmol) in ether (25 mL) with a DMF
(5 equiv., 0.52 mL, 6.40 mmol) quench. FCC (eluent; 50%
ether/hexane) gave the desired complex (14a) as bright red
crystals (0.320 g, 1.059 mmol, 83%), mp 93±948C. (Found:
C, 47.52; H, 3.06. C12H10CrO6 requires: C, 47.68; H,
3.31%). nmax (CHCl3)/cm21 1972vs, 1891vs (CuO),
1681s (CHO), 1267s (C±O-ether). dH (270 MHz) 10.04
(1H, s, CHO), 6.19 (1H, dd, Jˆ1.5, 6.4 Hz, ArC(3)H),
5.80 (1H, ddd, Jˆ1.5, 6.4, 6.9 Hz, ArC(5)H), 5.36 (1H,
dd, Jˆ0.5, 6.9 Hz, ArC(6)H), 5.25 (1H, d, Jˆ7.2 Hz, O±
CHH±O), 5.13 (1H, d, Jˆ7.2 Hz, O±CHH±O), 5.00 (1H, t,
Jˆ6.4 Hz, ArC(4)H), 3.53 (3H, s, OMe); dC (68 MHz) 230.6
(CO), 185.4 (CHO), 143.6 (ArC(1)±O), 95.7 (O±CH2±O),
95.2 (ArC(3)H), 92.2 (ArC(5)H), 84.7 (ArC(4)H), 86.2
(ArC(2)±C), 76.3 (ArC(6)H), 57.6 (OMe). m/z(CI) 320
(M11NH4), 303 (M11H), 167 (3032Cr(CO)3). Found:
M11H 302.9970. C12H11CrO6 requires: 302.9961.
(^)-h6-[2-Trimethylsilyl(methoxymethoxy)benzene]tri-
carbonylchromium(0) (16a). This complex was prepared
from h6-(methoxymethoxy)benzenetricarbonylchromium(0)
(7a, 0.27 g, 1.00 mmol) with a chlorotrimethylsilane
(5 equiv., 0.63 mL, 5.00 mmol) quench. FCC (eluent 2±
5% ether/hexane) and recrystallisation (from DCM/hexane)
furnished the complex (16a) as bright yellow crystals
(0.29 g, 0.84 mmol, 84%), mp 63±658C. (Found: C,
48.27; H, 5.20. C14H18CrO5Si requires: C, 48.55; H,
5.24%). nmax (Nujol)/cm21 1962vs (CuO ligand), 1877vs
(CuO ligand), 764m, 688m. dH (270 MHz) 5.65 (1H, ddd,
Jˆ1.5, 6.0, 7.5 Hz, ArC(5)H), 5.60 (1H, dd, Jˆ1.5, 7.0 Hz,
ArC(3)H), 5.28 (1H, d, Jˆ7.5 Hz, O±CHH±O), 5.17 (1H, d,
Jˆ7.5 Hz, O±CHH±O), 5.00 (1H, d, Jˆ7.5 Hz, ArC(6)H),
4.80 (1H, dd, Jˆ7.0, 6.0 Hz, ArC(4)H), 3.49 (3H, s, OMe),
0.34 (9H, s, TMS); dC (75 MHz) 145.1 (ArC(1)±O), 101.4
(ArC(3)H), 96.1 (O±CH2±O), 94.6 (ArC(5)H), 88.9
(ArC(2)±Si), 85.4 (ArC(4)H), 77.4 (ArC(6)H), 56.9
(OMe), 20.6 (TMS). m/z(EI) 346 (M1), 290
(M122£CO), 262 (M123£CO), 210 (M12Cr(CO)3),
201 (2622OCH2OMe), 73 (TMS), 52 (Cr). Found: M1
346.0332, C14H18CrO5Si requires: 346.0329.
(^)-h6-[2-Formyl-4-triisopropylsiloxymethyl(methoxy-
methoxy)benzene]tricarbonylchromium(0) (14b). This
complex was prepared from h6-[4-triisopropylsiloxymethyl
(methoxymethoxy)benzene]tricarbonylchromium(0) (7b,
300 mg, 0.65 mmol) with a DMF (5 equiv., 0.25 mL,
3.24 mmol) quench. The reaction was worked up with
water (10 mL). FCC (eluent: 20% ether/hexane) furnished
the complex (14b) as a bright orange crystalline solid
(193 mg, 0.40 mmol, 61%) mp 658C. (Found: C, 54.14; H,
6.79. C22H32CrO7Si requires: C, 54.08; H, 6.60%). nmax
(KBr)/cm21 3070w, 2943s, 2866s, 1982vs, 1904vs,
1885vs, 1673vs, 1540m, 1469s, 1084s, 954s, 803m, 607s,
522m. dH (270 MHz) 10.05 (1H, s, CHO), 6.27 (1H, d,
Jˆ1.7 Hz, ArC(3)H), 5.97 (1H, dd, Jˆ1.7, 6.9 Hz,
ArC(5)H), 5.37 (1H, d, Jˆ6.9 Hz, ArC(6)H), 5.24 (1H, d,
Jˆ6.9 Hz, O±CHH±O), 5.11 (1H, d, Jˆ7.2 Hz, O±CHH±
O), 4.49 (1H, d, Jˆ12.9 Hz, Ar±CH2), 4.42 (1H, d,
Jˆ12.6 Hz, Ar±CH2), 3.52 (3H, s, OMe), 1.31±0.71 (21H,
(^)-h6-[2-Trimethylsilyl-4-triisopropylsilyloxymethyl-
(methoxymethoxy)benzene]tricarbonylchromium(0)
(16b). This complex was prepared from h6-[4-triisopropyl-
siloxymethyl(methoxymethoxy)benzene]tricarbonylchro-
mium(0) (7b, 1.0 g, 2.16 mmol) in ether (20 mL) with a
chlorotrimethylsilane (5 equiv., 1.36 mL, 10.86 mmol)

I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
6129
quench. The reaction was worked up with water (10 mL).
FCC (eluent: 2% ether/hexane) furnished the complex (16b)
as a bright yellow crystalline solid (0.920g, 1.73 mmol,
80%) m.p 34±358C. (Found: C, 54.03; H, 7.46.
C24H40CrO6Si2 requires: C, 54.11; H, 7.57%). nmax (KBr)/
cm21 3096w, 2941s, 2865s, 1964vs, 1944vs, 1874vs,
1457m, 1245m, 1161s, 1111s, 981s, 841s, 666s, 627s,
535m. dH (270 MHz) 5.75 (1H, d, Jˆ6.9 Hz, ArC(5)H),
5.71 (1H, s, ArC(3)H), 5.28 (1H, d, Jˆ6.9 Hz, ArC(6)H),
5.14 (1H, d, Jˆ6.9 Hz, O±CHH±O), 4.97 (1H, d, Jˆ6.9 Hz,
O±CHH±O), 4.37 (2H, s, ArCH2), 3.46 (3H, s, OMe), 1.16±
0.97 (21H, m, TIPS), 0.32 (9H, s, TMS); dC (68 MHz) 233.7
(CO), 144.7 (ArC(1)±O), 104.1 (ArC(4)±CH2), 99.6
(ArC(3)H), 94.6 (O±CH2±O), 94.5 (ArC(5)H), 87.8
(ArC(2)±Si), 76.6 (ArC(6)H), 63.2 (Ar±CH2), 56.9
(OMe), 18.0 (TIPS±Me), 11.9 (Si±CH), 20.5 (TMS). m/z
(CI) 532 (M1), 448 (M123£CO), 396 (4482Cr), 223
(3962OTIPS). Found: M1 532.1767. C24H40CrO6Si2
requires: 532.1768.
CH2), 100.6 (ArC(3)H), 94.9 (O±CH2±O), 94.1 (ArC(5)H),
88.1 (ArC(2)±Si), 77.6 (ArC(6)H), 63.2 (Ar±CH2), 56.8
(OMe), 18.1 (TIPS±Me) 12.0 (Si±CH), 28.2 (Sn(Me)3).
m/z(CI) 620 (M1), 488 (M12Cr(CO)3), 473 (4882Me),
445 (473-iPr). Found: M1 624.1076. C24H40CrO6Si120Sn
requires: 624.1021.
(^)-h6-[2-Tributylstannyl(methoxymethoxy)benzene]-
tricarbonylchromium(0) (18a). This complex was
prepared from h6-(methoxymethoxy)benzenetricarbonyl-
chromium(0) (7a, 0.27 g, 1.00 mmol), with a tributyltin
chloride (1.4 equiv., 0.40 mL, 1.40 mmol) quench. The
reaction was worked up with saturated aqueous KF
(10 mL). FCC (eluent: 5% ether/hexane) furnished the
complex (18a) as a yellow oil (0.47 g, 0.84 mmol, 84%).
nmax (Nujol)/cm21 2956s, 1958vs, 1880, 664, 628. dH
(270 MHz) 5.59 (1H, dt, Jˆ1.2, 6.1 Hz, ArC(5)H), 5.49
(1H, dd, Jˆ1.5, 5.9 Hz, ArC(3)H), 5.33 (1H, dd, Jˆ0.5,
7.1 Hz, ArC(6)H), 5.14 (1H, d, Jˆ7.2 Hz, O±CHH±O),
4.93 (1H, d, Jˆ7.4 Hz, O±CHH±O), 4.85 (1H, dt, Jˆ0.5,
6.0 Hz, ArC(4)H), 3.46 (3H, s, OMe), 1.71±148 (6H, m,
CH2CH3), 1.45±1.23 (6, H, m, SnCH2CH2), 1.12 (6H, t,
Jˆ9.2 Hz, SnCH2), 0.90 (9H, t, Jˆ7.2 Hz, CH2CH3); dC
(75 MHz) 144.4 (ArC(1)±O), 102.7 (ArC(3)H), 95.7 (O±
CH2±O), 94.8 (ArC(4)H), 89.9 (ArC(2)±Sn), 87.2
(ArC(5)H), 78.5 (ArC(6)H), 56.8 (OMe), 28.9 (SnCH2CH2),
27.3 (CH2CH3), 13.6 (SnCH2), 0.8 (CH2CH3) m/z (CI) 564
(M11H), 507 (M12Bu1H), 393 (M122£CO22£Bu).
Found: M11H 564.0998. C23H37CrO5Sn requires:
564.0990.
(^)-h6-[2-Trimethylstannyl(methoxymethoxy)benzene]-
tricarbonylchromium(0) (17a). This complex was
prepared from h6-(methoxymethoxybenzene)tricarbonyl-
chromium(0) (7a, 0.350 g, 1.28 mmol) in ether (25 mL)
with a trimethyltin chloride (2 equiv., 0.514 g, 2.55 mmol)
quench. FCC (eluent: 2% ether/hexane) gave the complex
(17a) was obtained as bright yellow crystals (0.539 g,
1.23 mmol, 95%), mp 80±828C (Found: C, 38.66; H, 4.27.
C14H18O5CrSn requires: C, 38.48; H, 4.15%). nmax (CHCl3)/
cm21 1963vs, 1886vs. dH (270 MHz) 5.59 (1H, ddd, Jˆ1.5,
6.1, 6.7 Hz, ArC(5)H), 5.50 (1H, dd, Jˆ1.5, 5.9 Hz,
ArC(3)H), 5.32 (1H, dd, Jˆ0.7, 6.7 Hz, ArC(6)H), 5.15
(1H, d, Jˆ7.2 Hz, O±CHH±O), 4.94 (1H, d, Jˆ7.2 Hz,
O±CHH±O), 4.85 (1H, ddd, Jˆ0.7, 5.9, 6.1 Hz,
ArC(4)H), 3.46 (3H, s, OMe), 0.36 (9H, Sn(Me)3); dC
(68 MHz) 234.1 (CO), 144.5 (ArC(1)±O), 102.5
(ArC(3)H), 95.8 (O±CH2±O), 94.8 (ArC(5)H), 87.1
(ArC(4)H), 89.0 (ArC(2)Sn), 78.4 (ArC(6)H), 56.9 (OMe),
28.2 (Sn(Me)3). m/z (FAB1) 119Sn 438 (M1), 382
(M122£CO), 354 (M123£CO); 117Sn 438 (M1), 380
(M122£CO), 352 (M123£CO). Found: M1 437.9598.
C14H18CrO5Sn requires: 437.9581.
(^)-h6-[2-Hydroxymethyl(methoxymethoxy)benzene)-
tricarbonylchromium(0) (19a). This complex was
prepared from h6-(methoxymethoxybenzene)tricarbonyl-
chromium(0) (7a, 0.27 g, 1.00 mmol), treated as described
except that the temperature of the solution was raised to
2428C for a quench with paraformaldehyde (5 equiv.,
0.15 g, 5.00 mmol). FCC (eluent: 60±80% ether/hexane)
and recrystallisation (from DCM/hexane) furnished the
complex (19a) as bright yellow crystals (0.16 g,
0.53 mmol, 53%), mp 44±468C. (Found: C, 47.28; H,
3.68. C12H12CrO6 requires: C, 47.36; H, 3.94%). nmax
(Nujol)/cm21 3400brs (OH), 1964vs, 1865vs, 666s. dH
(270 MHz) 5.73 (1H, dd, Jˆ1.2, 6.2 Hz, ArC(3)H), 5.50±
5.41 (2H, m, ArC(5,6)H), 5.16 (1H, d, Jˆ6.9 Hz, O±
CHHO), 5.06 (1H, d, Jˆ6.9 Hz, O±CHH±O), 4.96 (1H,
dt, Jˆ1.2, 6.2 Hz, ArC(4)H), 4.64 (1H, dd, Jˆ6.7,
13.4 Hz, Ar±CH2), 4.41 (1H, dd, Jˆ5.9, 13.4 Hz, Ar±
CH2), 3.52 (3H, s, OMe), 1.97 (1H, t, Jˆ6.4 Hz, OH); dC
(75 MHz) 139.1 (ArC(1)±O), 100.3 (ArC(2)±CH2), 95.7
(O±CH2±O), 94.4 (ArC(5)H), 93.7 (ArC(3)H), 86.3
(ArC(4)H), 78.6 (ArC(6)H), 59.6 (Ar±CH2), 57.1 (OMe).
m/z(EI) 304 (M1), 248 (M122£CO), 220 (M123£CO,
189 (2202 CH2OH), 159 (2202OCH2OMe). Found: M1
304.0038. C12H12CrO6 requires: 304.0039.
(^)-h6-[2-Trimethylstannyl-4-triisopropylsiloxymethyl-
(methoxymethoxy)benzene]tricarbonylchromium(0)
(17b). This complex was prepared from h6-[4-triisopropyl-
siloxymethyl(methoxymethoxy)benzene]tricarbonylchro-
mium(0) (7b, 1.0 g, 2.16 mmol) in 20 mL THF was treated
as described, quenching over night with a solution of chloro-
trimethyltin (2 equiv., 0.86 g, 4.32 mmol) in 5 mL THF.
The reaction was worked-up with saturated potassium ¯uo-
ride solution (10 mL). Chromatography (eluent: 5% ether/
hexane) furnished the title complex (17b) as a bright yellow
crystalline solid (0.96 g, 1.54 mmol, 72%) mp 318C.
(Found: C, 46.27; H, 6.67. C24H40CrO6SiSn requires: C,
46.15; H, 6.46%). nmax (KBr)/cm21 3104w, 2943s, 2866s,
1957vs, 1877vs, 1457m, 1259m, 1159s, 1082s, 981s, 811s,
668s, 534s. dH (270 MHz) 5.70 (1H, d, Jˆ6.2 Hz,
ArC(5)H), 5.63 (1H, s, ArC(3)H), 5.33 (1H, d, Jˆ6.6 Hz,
ArC(6)H), 5.13 (1H, d, Jˆ7.1 Hz, O±CHH±O), 4.93 (1H, d,
Jˆ6.9 Hz, O±CHH±O), 4.39 (2H, s, Ar±CH2), 3.45 (3H, s,
OMe), 1.16±0.97 (21H, m, TIPS), 0.36 (9H, s, TMS); dC
(68 MHz) 234.1 (CO), 144.9 (ArC(1)±O), 105.9 (ArC(4)±
(^)-h6-[2-Hydroxymethyl-4-triisopropylsiloxymethyl-
(methoxymethoxy)benzene]tricarbonylchromium(0) (19b).
This complex was prepared from h6-[4-triisopropylsiloxy-
methyl(methoxymethoxy)benzene]tricarbonylchromium(0)
(7b, 300 mg, 0.65 mmol with a paraformaldehyde (5 equiv.,
97 mg, 3.24 mmol) quench. The reaction was worked up
with water (10 mL). FCC (eluent: 60% ether/hexane)

6130
I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
furnished the complex (19b) as a bright yellow crystalline
solid (228 mg, 0.47 mmol, 72%) mp 41±428C. (Found: C,
54.07; H, 6.55. C22H34CrO7Si requires: C, 53.86; H, 6.99%).
nmax (KBr)/cm21 3265w. 2944s, 2866s, 1936vs, 1874vs,
1858vs, 1466s, 1240s, 1158s, 989s, 670s, 538m, dH
(270 MHz) 5.77 (1H, s, ArC(3)H), 5.58 (1H, d, Jˆ6.7 Hz,
ArC(5)H), 5.44 (1, H, d, Jˆ6.9 Hz, ArC6)H), 5.12 (1H, d,
Jˆ7.0 Hz, O±CHH±O), 5.03 (1H, d, Jˆ6.6 Hz, O±CHH±
O), 4.67 (1H, s, Ar±CH2), 4.63 (1H, s, Ar±CH2), 4.48 (1H,
d, Jˆ12.9 Hz, Ar±CH2±OH), 4.41 (1H, d, Jˆ12.9 Hz, Ar±
CH2±OH), 3.49 (3, H, s, OMe), 1.97 (1H, s, OH), 1.32±0.83
(21H, m, TIPS; dC (68 MHz) 233.0 (CO), 138.2 (ArC(1)±
O), 105.7 (ArC(4)±CH2), 99.8 (ArC(2)±CH2±OH), 95.9
(O±CH2±O), 92.5 (ArC(5)H), 91.4 (ArC(3)H), 78.2
(ArC(6)H), 63.0 (Ar±CH2), 59.9 (Ar±CH2±OH), 57.1
(OMe), 18.0 (TIPS±Me), 11.9 (Si±CH). m/z(CI) 490 (M1),
473 (M12OH), 406 (M123£CO), 337 (4732Cr(CO)3).
Found: M1 490.1442. C22H34CrO7Si requires: 490.1478.
138.4 (Ph(C)±COH), 128.4±127.2 (Ph(C)H), 108.9
(ArC(4)±CH2), 102.1 (ArC(2)±COH), 96.7 (ArC(3)H),
94.8 (O±CH2±O), 92.8 (ArC(5)H), 80.4 (C±OH), 75.9
(ArC(6)H), 63.1 (Ar±CH2), 56.5 (OMe), 18.0 (TIPS±Me),
11.9 (Si±CH). m/z(FAB1) 642 (M1), 625 (M12OH), 558
(M123£CO), 541 (62523£CO), 489 (6252Cr(CO)3).
Found: M1 642.2108. C34H42CrO7Si requires: 642.2105.
(^)-h6-[2-(Di-4-methoxyphenylhydroxymethyl)(methoxy-
methoxy)benzene]tricarbonylchromium(0) (21a). This
complex was prepared from h6-(methoxymethoxybenzene)-
tricarbonyl-chromium(0) (7a, 0.350 g, 1.28 mmol) in ether
(25 mL) with a 4-40-dimethoxybenzophenone (5 equiv.,
1.547 g, 6.40 mmol) quench. FCC (eluent: 50% ether/
hexane) gave the complex (21a) as yellow crystals
(0.608 g, 1.177 mmol, 92%), mp 170±1728C. (Found: C,
60.47; H, 4.54. C26H24CrO8 requires: C, 60.47; H, 4.68%).
nmax (CHCl3)/cm21 3423w, 1970vs, 1897vs, 1251s. dH
(270 MHz) 7.30±7.21 (4H, m, PhC(2,6)H), 6.84 (4H, t,
Jˆ8.5 Hz, PhC(3,5)H), 5.55 (1H, t, Jˆ6.3 Hz, ArC(5)H),
5.27 (1H, d, Jˆ6.3 Hz, ArC(3)H), 4.97 (1H, d, Jˆ7.2 Hz,
O±CHH±O), 4.79 (1H, d, Jˆ7.2 Hz, O±CHH±O), 4.78
(1H, d, Jˆ6.3 Hz, ArC(6)H), 4.61 (1H, t, Jˆ6.3 Hz,
ArC(4)H), 4.50 (1H, s, OH), 3.79 (6H, s, PhOMe), 3.10
(3H, s, OMe); dC (68 MHz) 232.7 (CO), 159.3, 158.8
(PhC±OMe), 139.0, 138.2 (PhC±C), 135.2 (ArC(1)±O),
129.7, 128.3, 113.2, 113.1 (PhC±H), 109.6 (ArC(2)±C),
98.3 (ArC(3)H), 95.0 (O±CH2±O), 94.7 (ArC(5)H), 83.2
(ArC(4)H), 79.7 (C±OH), 76.6 (ArC(6)H), 56.8 (OMe),
55.3 (PhOMe). m/z (FAB1) 516 (M1), 499 (M12OH),
432 (M123£CO), 415 (M123£CO2OH). Found:
516.0879. C26H24CrO8 requires: 516.0876.
(^)-h6-[2-(Diphenylhydroxymethyl)(methoxymethoxy)-
benzene]tricarbonylchromium(0) (20a). This complex
was prepared from h6-(methoxymethoxybenzene)tricarbo-
nylchromium(0) (7a, 0.350 g, 1.28 mmol) in ether (25
mL) with a benzophenone (5 equiv., 0.465 g, 6.40 mmol)
quench. FCC (eluent: 15% ether/hexane) gave the complex
(20a) as yellow crystals (0.546 g, 1.196 mmol, 94%), mp
164±1668C. (Found: C, 63.27; H, 4.67. C24H20CrO6
requires: C, 63.16; H, 4.42%). nmax (CHCl3)/cm21 3386m,
1971vs, 1898vs, 1265s. dH (270 MHz) 7.23±7.42 (10H, m,
PhH), 5.55 (1H, dt, Jˆ1.2, 6.3 Hz, ArC(5)H), 5.26 (1H, dd,
Jˆ1.2, 6.8 Hz, ArC(3)H), 4.97 (1H, d, Jˆ6.9 Hz, O±CHH±
O) 4.78 (1H, d, Jˆ7.2 Hz, O±CHH±O), 4.77 (1H, d,
Jˆ5.9 Hz, ArC(6)H), 4.60 (1H, dt, Jˆ1.0, 6.3, Hz,
ArC(4)H), 4.51 (1H, s, OH), 3.03 (3H, s, OMe); dC
(68 MHz) 232.5 (CO), 146.5 (PhC±C), 142.3 (PhC±C),
138.1 (ArC(1)±O), 128.4, 128.1, 128.0, 127.5, 127.1
(PhCH), 108.95 (ArC(2)±C), 98.2 (ArC(3)H), 94.8 (O±
CH2±O), 94.7 (ArC(5)H), 82.87 (ArC(4)H), 80.13 (C±
OH), 76.59 (ArC(6)H), 56.58 (C, OMe). m/z (FAB1) 456
(M1), 372 (M123£CO), 355 (M123£CO2OH), 327
(^)-h6-[2-(Phenylhydroxymethyl)methoxymethoxyben-
zene]tricarbonylchromium(0) (22a). This complex was
prepared from h6-(methoxymethoxy)benzenetricarbonyl-
chromium(0) (7a, 0.350 g, 1.28 mmol) in ether (25 mL)
with a benzaldehyde (5 equiv., 0.650 mL, 6.40 mmol)
quench. FCC (eluent: 80% ether/hexane) gave the complex
(22a) as yellow crystals (0.354 g, 0.931 mmol, 73%), mp
127±1298C. (Found: C, 56.72; H, 4.19. C18H16CrO6
requires: C, 56.85; H, 4.24%). nmax (CHCl3)/cm21 3597br,
1969vs, 1888vs, 1263s. dH (270 MHz) 7.56±7.32 (5H, m,
PhH), 5.94 (1H, s, ArC(2)±C±H), 5.47 (1H, t, Jˆ6.2 Hz,
ArC(5)H), 5.33 (1H, d, Jˆ6.2 Hz, ArC(3)H), 5.22 (1H, d,
Jˆ6.9 Hz, O±CHH±O), 5.12 (1H, d, Jˆ6.9 Hz, O±CHH±O),
5.03 (1H, d, Jˆ6.2 Hz, ArC(6)H), 4.73 (1H, t, Jˆ6.2 Hz,
ArC(4)H), 3.53 (3H, s, OMe); dC (68 MHz) 232.5 (CO),
140.1 (PhC(1)±C), 139.0 (ArC(1)±O), 128.4, 128.3, 127.0
(PhCH), 103.2 (ArC(2)±C), 96.0 (ArC(3)H), 95.1 (O±CH2±
O), 94.5 (ArC(5)H), 85.1 (ArC(4)H), 77.2 (ArC(6)H), 70.8
(C±OH), 57.3 (Me). m/z (FAB1) 380 (M1), 363 (M12OH),
296 (M123£CO). Found: M1 380.0362. C18H16CrO6
requires: 380.0352.
(M123£CO2CH2OCH3).
Found:
M1
456.0671.
C24H20CrO6 requires 456.0665.
(^)-h6-[2-(Diphenylhydroxymethyl)-4-triisopropylsiloxy-
methyl(methoxymethoxy)benzene]tricarbonylchromium(0)
(20b). This complex was prepared from h6-[4-triisopropyl-
siloxymethyl(methoxymethoxy)benzene]tricarbonylchro-
mium(0) (7b, 300 mg, 0.65 mmol) with a quench with a
solution of benzophenone (5 equiv., 594 mg, 3.24 mmol)
in 3 mL THF. The reaction was worked-up with water
(10 mL). FCC (eluent: 10% ether/hexane) furnished the
complex (20b) as a bright yellow crystalline solid
(349 mg, 0.55 mmol, 84%) mp 108±1098C. (Found: C,
63.52; H, 6.73. C34H42CrO7Si requires: C, 63.53; H,
6.59%). nmax (KBr)/cm21 3557m, 3060w, 2943s, 2865s,
1965vs, 1882vs, 1459s, 1160s, 1086s, 964m, 757s, 701s,
666s, 475m. dH (270 MHz) 7.62±7.23 (10H, m, PhH),
5.68 (1H, dd, Jˆ1.7, 6.7 Hz, ArC(5)H), 5.27 (1H, d,
Jˆ6.7 Hz, ArC(6)H), 4.95 (1H, d, Jˆ6.9 Hz, O±CHH±O),
4.92 (1H, d, Jˆ1.7 Hz, ArC(3)H), 4.75 (1H, d, Jˆ7.2 Hz,
O±CHH±O), 4.60 (1H, s, OH), 4.23 (2H, s, Ar±CH2), 3.02
(3H, s, OMe), 1.03±0.95 (21H, m, TIPS); dC (68 MHz)
232.6 (CO), 147.2 (ArC(1)±O), 142.4 (Ph(C)±COH),
Crystal data for (22a): C18H16O6Cr, Mˆ380.3, monoclinic,
space group P21/c (no. 14), aˆ12.488(1), bˆ13.908(1),
Ê
Ê 3
cˆ10.017(1) A, bˆ92.05(1)8, Vˆ1738.6(3) A , Zˆ4,
Dcˆ1.453 g cm23, m(Mo-Ka)ˆ6.88 cm21, F(000)ˆ784,
Tˆ293 K; yellow blocks, 0.37£0.35£0.33 mm3, Siemens
P4/PC diffractometer, v-scans, 3059 independent re¯ec-
tions. The structure was solved by direct methods and the
non-hydrogen atoms were re®ned anisotropically using full

I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
6131
matrix least-squares based on F2 to give R1ˆ0.046,
wR2ˆ0.107 for 2199 independent observed re¯ections
[uFou.4s(uFou), 2uˆ508] and 218 parameters.
PhH), 7.78±7.75 (2H, m, PhH), 6.04 (1H, d, Jˆ4.1 Hz,
ArC(2)±C±H), 5.52 (1H, dt, Jˆ1.1, 6.4 Hz, ArC(5)H),
5.35 (1H, dd, Jˆ1.1, 6.4 Hz, ArC(3)H), 5.23 (1H, d,
Jˆ6.9 Hz, O±CHH±O), 5.14 (1H, d, Jˆ6.9 Hz, O±CHH±
O), 4.99 (1H, dd, Jˆ1.1, 6.4 Hz, ArC(6)H), 4.76 (1H, dt,
Jˆ1.1, 6.4 Hz, ArC(4)H), 3.54 (3H, s, OMe), 3.09 (1H, d,
Jˆ4.1 Hz, OH); dC (68 MHz) 232.6 (CO), 146.3 (PhC(4)±
N), 139.9 (PhC(1)±C), 132.8 (ArC(1)±O), 127.2 (PhCH),
123.9 (PHCH), 105.8 (ArC(2)±C), 95.6 (O±CH2±O), 94.2
(ArC(3)H), 91.4 (ArC(5)H), 86.0 (ArC(4)H), 77.4
(ArC(6)H), 67.9 (C±OH), 57.2 (OMe). m/z (FAB1) 435
(M1), 341 (M123£CO). Found: M1 425.0203.
C18H15CrNO8 requires: 425.0202.
(^)-h6-[2-(4-Methoxyphenylhydroxymethyl)(methoxy-
methoxy)benzene]tricarbonylchromium(0) (23a). This
complex was prepared from h6-(methoxymethoxy)benzene-
tricarbonyl-chromium(0) (7a, 0.350 g, 1.28 mmol) in ether
(25 mL) with a 4-methoxybenzaldehyde (5 equiv., 0.77 mL,
6.40 mmol) quench. FCC (eluent: 80% ether/hexane) gave
the complex (23a) was obtained as yellow crystals (0.436 g,
1.062 mmol, 83%), mp 118±1208C. (Found: C 55.70, H
4.36. C19H18CrO7 requires: C 55.61, H 4.42%). nmax
(CDCl3)/cm21 3584br, 1969, 1894, 1252. dH (270 MHz3)
7.45 (2H, d, Jˆ8.7 Hz, PhH), 6.94 (2H, d, Jˆ8.7 Hz,
PhH), 5.89 (1H, d, Jˆ3.5 Hz, ArC(2)±C±H), 5.45 (1H, dt,
Jˆ1.2, 6.4 Hz, ArC(5)H), 5.33 (1H, d, Jˆ6.4 Hz, ArC(3)H),
5.21 (1H, d, Jˆ6.9 Hz, O±CHH±O), 5.11 (1H, d, Jˆ6.9 Hz,
O±CHH±O), 5.02 (1H, dd, Jˆ1.1, 6.4 Hz, ArC(6)H), 4.74
(1H, t, Jˆ6.4 Hz, ArC(4)H), 3.81 (3H, s, PhOMe), 3.53 (3H,
s, OMe), 3.04 (1H, d, Jˆ3.5 Hz, ±OH); dC (68 MHz) 232.6
(CO), 159.5 (PhC(4)±C), 140.2 (PhC(1)±C), 131.1
(ArC(1)±O), 128.2 (PhCH), 113.8 (PhCH), 103.8
(ArC(2)±C), 96.0 (ArC(3)H), 95.0 (O±CH2±O), 94.5
(ArC(5)H), 85.3 (ArC(4)H), 77.3 (ArC(6)H), 70.5 (C±
OH), 57.3 (OMe), 55.4 (PhOMe). m/z (FAB1) 410 (M1),
393 (M12OH), 326 (M123£CO). Found: M1 410.0458
C19H18CrO7 requires: 410.0473.
(^)-h6-[2-(N,N-Dimethylaminomethyl)-4-triisopropyl-
siloxymethyl(methoxymethoxy)benzene]tricarbonyl-
chromium(0) (26b). This complex was prepared from
h6-[4-triisopropylsiloxymethyl(methoxymethoxy)benzene]-
tricarbonylchromium(0) (7b, 300 mg, 0.65 mmol) with a
quench with Eschenmoser salt (300 mg, 1.62 mmol). The
reaction was worked up with water (10 mL). FCC (eluent:
30% ether/hexane) furnished the complex (26b), as a yellow
oil (209 mg, 0.40 mmol, 61%). nmax (neat)/cm21 3101w,
2944s, 2866s, 2775m, 1962vs, 1881vs, 1464s, 1197s,
1082s, 977s, 882s, 667s, 532m. dH (270 MHz) 5.69 (1H,
d, Jˆ1.7 Hz, ArC(3)H), 5.53 (1H, dd, Jˆ1.5, 6.9 Hz,
ArC(5)H), 5.43 (1H, d, Jˆ6.9 Hz, ArC(6)H), 5.08 (1H, d,
Jˆ6.9 Hz, O±CHH±O), 5.00 (1H, d, Jˆ6.9 Hz, O±CHH±
O), 4.47 (1H, s, Ar±CH2), 4.43 (1H, s, Ar±CH2), 3.47 (3H,
s, OMe), 3.04 (1H, s, CH2±N), 2.99 (1H, s, Ar±CH2±N),
2.31 (6H, s, N(Me)2), 1.17±1.03 (21H, m, TIPS); dC
(68 MHz) 233.3 (CO), 138.3 (ArC(1)±O), 106.3 (ArC(4)±
CH2), 97.8 (ArC(2)±CH2±N), 95.8 (ArC(3)H), 94.5 (O±
CH2±O), 91.3 (ArC(5)H), 78.4 (ArC(6)H), 63.1 (Ar±
CH2), 57.1 (CH2±N), 56.9 (OMe), 45.7 (N(Me)2), 18.0
(TIPS±Me), 11.9 (Si±CH). m/z (FAB1) 518 (M11H),
490 (M12CO), 433 (M123£CO), 403, 389, 162, 58.
Found, M11H: 518.2035. C21H40CrNO6Si requires:
518.2030.
(^)-h6-[2-(2,6-Dimethoxyphenylhydroxymethyl)(methoxy-
methoxy)benzene]tricarbonylchromium(0) (24a). This
complex was prepared from h6-(methoxymethoxy)benzene-
tricarbonylchromium(0) (7a, 0.350 g, 1.28 mmol) in ether
(25 mL) with a 2,6-dimethoxybenzaldehyde (5 equiv.,
1.063 g, 6.40 mmol) quench. FCC (eluent: 50% Et2O:
50% hexane) gave the complex (24a) as yellow crystals
(0.452 g, 1.028 mmol, 80%), mp 145±1478C. (Found: C,
54.51; H, 4.48. C20H20CrO8 requires: C, 54.55; H, 4.58%).
nmax (CHCl3)/cm21 3533br, 1965vs, 1884vs, 1233s. dH
(270 MHz) 7.29 (1H, t, Jˆ8.4 Hz, PhH), 6.65 (2H, d,
Jˆ8.4 Hz, PhH), 6.10 (1H, s, ArC(1)±C±H), 5.52 (1H, t,
Jˆ6.2 Hz, ArC(5)H), 5.36 (1H, d, Jˆ6.2 Hz, ArC(3)H),
5.31 (1H, d, Jˆ6.9 Hz, O±CHH±O), 5.27 (1H, d,
Jˆ6.9 Hz, O±CHH±O), 5.16 (1H, d, Jˆ6.2 Hz, ArC(6)H),
4.60 (1H, t, Jˆ6.2 Hz, ArC(4)H), 3.89 (6H, s, PhOMe, 3.56
(3H, s, OMe); dC (68 MHz) 232.9 (CO), 157.9 (PhC±C),
142.0 (ArC(1)±O), 129.7 (PhCH), 114.4 (PhC±O), 104.2,
103.9 (PhCH), 98.8 (ArC(2)±C), 96.3 (ArC(3)H), 95.8 (O±
CH2±O), 95.5 (ArC(5)H), 83.2 (ArC(4)H), 77.1 (ArC(6)H),
64.3 (C±OH), 57.1 (OMe), 55.6 (PhOMe). m/z (FAB1): 440
(M1), 423 (M12OH), 384 (M122£CO), 356 (M12
3£CO). Found: M1 440.0563 C20H20CrO8 requires:
440.0563.
(^)-h6-[2-(N-Phenyl-a-aminobenzyl)(methoxymethoxy)-
benzene]tricarbonylchromium(0) (27a). This complex
was prepared from h6-(methoxymethoxy)benzenetricarbo-
nylchromium(0) (7a, 0.350 g, 1.28 mmol) in ether (25 mL)
with a N-benzylideneaniline (5 equiv., 1.159 g, 6.40 mmol)
quench. FCC (eluent: 25±30% ether/hexane) gave the
complex (27a) as yellow crystals (0.555 g, 1.22 mmol,
95%), mp 162±1648C. (Found: C, 63.57; H, 4.70; N, 3.06.
C24H21CrNO5 requires: C, 63.29; H, 4.65; N, 3.08%). nmax
(CHCl3)/cm21 3423, 1969, 1894, 1248. dH (270 MHz)
7.32±7.62 (5H, m, C±PhCH), 7.14±6.53 (5H, m, N±
PhH), 5.61 (1H, s, N±H), 5.50 (1H, t, Jˆ6.3 Hz,
ArC(5)H), 5.29 (1H, d, Jˆ6.3 Hz, ArC(3)H), 5.25 (1H, d,
Jˆ6.3 Hz, ArC(6)H), 5.16 (1H, d, Jˆ7.1 Hz, O±CHH±O),
5.02 (1H, d, Jˆ7.1 Hz, O±CHH±O), 4.72 (1H, t, Jˆ6.3 Hz,
ArC(4)H), 4.21 (1H, s, ArC(2)±CH), 3.41 (3H, s, OMe); dC
(68 MHz) 232.5 (CO), 147.2 (PhC(1)±N), 140.0 (PhC(1)±
C), 139.6 (ArC(1)±O), 129.2, 128.7, 127.8 (PhC±C), 128.0,
118.2, 113.7 (PhC±N), 103.7 (ArC(2)±C), 96.1 (ArC(3)H),
95.4 (O±CH2±O), 95.0 (ArC(5)H), 84.3 (ArC(4)H),
76.4(ArC(6)H), 57.1 (ArC(2)±C±H), 56.5 (OMe). m/z
(FAB1) 455 (M1), 371 (M123£CO). Found: M1
455.0831. C24H21CrNO5 requires: 455.0825.
(^)-h6-{2-[4-Nitrophenyl)hydroxymethyl](methoxymeth-
oxy)benzene}tricarbonylchromium(0)
(25a).
This
complex was prepared from h6-(methoxymethoxy)benzene-
tricarbonylchromium(0) (7a, 0.350 g, 1.28 mmol) in ether
(25 mL) with a 4-nitrobenzaldehyde (5 equiv., 0.963 g,
6.40 mmol) quench. FCC (80% ether/hexane) gave the
complex (25a) as orange crystals (0.375 g, 0.088 mmol,
69%), mp 176±1788C. nmax (CHCl3)/cm21 3425br,
1973vs, 1902vs, 1384s. dC (270 MHz) 8.26±8.32 (2H, m,

6132
I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
(^)-h6-[-2-Iodo(methoxymethoxy)benzene]tricarbonyl-
chromium(0) (28a). This complex was prepared from
h6-(methoxymethoxy)benzenetricarbonylchromium(0) (7a,
0.27 g, 1.00 mmol) in ether (10 mL) with a quench of a
solution of 1,2-diiodoethane (1.2 equiv., 0.34 g,
1.20 mmol) in ether (1 mL). The reaction was worked-up
with saturated aqueous sodium thiosulphate (5 mL)
followed immediately with FCC (eluent: 5±10% ether/hex-
ane) and recrystallisation (from DCM/hexane) to furnish the
complex (28a) as bright yellow crystals (0.33 g, 0.83 mmol,
83%), mp 107±1098C. nmax (Nujol)/cm21 2923vs, 1953vs,
1893vs, 1086m, 723w. dH (300 MHz) 5.92 (1H, dd, Jˆ0.99,
6.18 Hz, ArC(3)H), 5.48±5.39 (2H, m, ArC(5,6)H), 5.21
(1H, d, Jˆ6.93 Hz, O±CHH±O), 5.10 (1H, d, Jˆ6.93 Hz,
O±CHH±O), 4.82 (1H, dt, Jˆ1.24, 5.56 Hz, ArC(4)H), 3.56
(3H, s, OMe); dC (75 MHz) 138.8 (ArC(1)±O), 102.8
(ArC(3)H), 96.2 (O±CH2±O), 92.8 (ArC(5)H), 87.6
(ArC(4)H), 80.6 (ArC(2)±I), 77.9 (ArC(6)H), 57.2 (OMe).
m/z(EI) 400 (M1), 368 (M12MeOH), 316 (M123£CO),
264 (M12Cr(CO)3), 52 (Cr), 28 (CO). Found: M1
399.8906. C11H9CrIO5 requires: 399.8900.
95.2 (O±CH2±O), 94.4 (ArC(3)H), 92.2 (ArC(5)H), 84.6
(ArC(4)H), 86.2 (ArC(2)±C), 76.4 (ArC(6)H), 66.0 (O±
CH2), 15.0 (Me). m/z: (FAB1) 316 (M1), 232
(M123£CO). Found: M1 316.0038. C13H12CrO6 requires
316.0039.
(^)-h6-[2-Formyl-4-triisopropylsiloxymethyl(ethoxy-
methoxy)benzene]tricarbonylchromium(0) (29b). This
complex was prepared from h6-[4-(triisopropylsiloxy-
methyl)(ethoxymethoxy)benzene]tricarbonylchromium(0)
(8b, 308 mg, 0.65 mmol) in ether (10 mL) with a DMF
(2 equiv., 0.13 mL, 1.3. mmol) quench. The reaction was
worked-up with water (10 mL). FCC (eluent: 20% ether/
hexane) furnished the complex (29b) as a bright orange
crystalline solid (200 mg, 0.40 mmol, 62%) mp 72±748C.
(Found: C, 55.09; H, 7.00. C23H34CrO7Si requires: C, 54.96;
H, 6.82%). nmax (KBr)/cm21 2943s, 2866s, 1988vs, 1913vs,
1896vs, 1677s, 1468s, 1236s, 1084s, 948s, 665s, 518m. dH
(270 MHz) 10.04 (1H, s, CHO), 6.26 (1H, d, Jˆ2.0 Hz,
ArC(3)H), 5.96 (1H, dd, Jˆ2.0, 6.9 Hz, ArC(5)H), 5.41
(1H, d, Jˆ6.9 Hz, ArC(6)H), 5.27 (1H, d, Jˆ7.4 Hz, O±
CHH±O), 5.17 (1H, d, Jˆ7.4 Hz, O±CHH±O), 4.48 (1H,
d, Jˆ12.9 Hz, Ar±CH2), 4.42 (1H, d, Jˆ12.9 Hz, Ar±CH2),
3.75 (2H, q, Jˆ7.2 Hz, O±CH2), 1.24 (3H, t, Jˆ7.2 Hz,
Me), 1.23±1.01 (21H, m, TIPS); dC (68 MHz) 230.8 (CO),
185.7 (CHO), 141.1 (ArC(1)±O), 104.0 (ArC(4)±CH2),
94.4 (O±CH2±O), 93.4 (ArC(3)H), 90.0 (ArC(5)H), 86.2
(ArC(2)±CHO), 75.7 (ArC(6)H), 65.9 (Ar±CH2), 62.8
(O±CH2), 18.0 (TIPS±Me), 14.9 (Me), 11.9 (Si±CH). m/z
(CI) 520 (M11NH4), 503 (M11H), 418 (M123£CO), 381,
367 (5032Cr(CO)3), 337, 329, 271. Found: M11H
503.1551. C23H35CrO7Si requires: 503.1557.
(^)-h6-[2-(Iodo(4-triisopropylsiloxymethyl)(methoxy-
methoxy)benzene]tricarbonylchromium(0) (28b). This
complex was prepared from h6-[(4-triisopropylsiloxy-
methyl)(methoxymethoxy)benzene]tricarbonylchromium(0)
(7b, 2 g, 4.32 mmol) with an overnight quench with a solu-
tion of 1,2-diiodoethane (1.2 equiv., 1.5 g, 5.32 mmol) in
4 mL THF. The reaction was worked-up with saturated
aqueous sodium thiosulphate (20 mL). FCC (eluent: 1%
ether/hexane) furnished the complex (28b) as a bright
yellow crystalline solid (2.40 g, 4.07 mmol, 95%). mp
62±638C. (Found: C, 43.45; H, 5.25. C21H31CrIO6Si
requires: C, 43.01; H, 5.33%). nmax (KBr)/cm21 3106w,
3074w, 2943s, 2864s, 1969vs, 1893vs, 1865vs, 1466s,
1083s, 970s, 801m, 619s, 531m. dH (270 MHz) 5.99 (1H,
s, ArC(3)H), 5.45±5.43 (2H, m, ArC(5,6)H), 5.16 (1H, d,
Jˆ6.9 Hz, O±CHH±O), 5.07 (1H, d, Jˆ6.9 Hz, O±CHH±
O), 4.44 (1H, s, Ar±CH2), 4.43 (1H, s, Ar±CH2), 3.52 (3H,
s, OMe), 1.16±0.97 (21H, m, TIPS); dC (68 MHz) 232.5
(CO), 138.1 (ArC(1)±O), 107.2 (ArC(4)±CH2), 100.9
(ArC(3)H), 96.4 (O±CH2±O), 90.7 (ArC(5)H), 80.2
(ArC(2)±I), 77.5 (ArC(6)H), 62.6 (Ar±CH2), 57.2 (OMe),
18.0 (TIPS±Me), 11.9 (Si±CH). m/z(CI) 604 (M11NH4),
587 (M11H), 586 (M1), 460 (M11H2I). Found: M1
586.0343. C21H31CrIO6Si requires: 586.0339.
(^)-h6-[2-(Diphenylhydroxymethyl)(ethoxymethoxy)-
benzene]tricarbonylchromium(0) (30a). This complex
was prepared from h6-[(ethoxymethoxy)benzene]tricarbo-
nylchromium(0) (8a, 0.369 g, 1.28 mmol) in ether
(25 mL) with a benzophenone (5 equiv., 1.16 g, 6.40
mmol) quench. FCC (eluent: 15% ether/hexane) gave the
complex (30a) as yellow crystals (0.492 g, 1.048 mmol,
82%), mp 168±1708C (Found: C, 63.97; H, 4.78.
C25H22CrO6 requires: C, 63.83; H, 4.71%). nmax (CHCl3)/
cm21 3151 br, 1971vs, 1898vs, 1261s. dH (270 MHz) 7.39±
7.24 (10H, m, PhH), 5.56 (1H, t, Jˆ6.3 Hz, ArC(5)H), 5.30
(1H, d, Jˆ6.3 Hz, ArC(3)H), 4.99 (1H, d, Jˆ7.1 Hz, O±
CHH±O), 4.85 (1H, d, Jˆ7.1 Hz, O±CHH±O) 4.76 (1H,
d, Jˆ6.3 Hz, ArC(6)H), 4.61 (1H, t, Jˆ6.3 Hz, ArC(4)H),
4.61 (1H, s, OH), 3.31 (1H, m, O±CH2), 3.08 (1H, m, O±
CH2), 1.01 (3H, t, Jˆ7.1 Hz, Me); dC (68 MHz) 232.6 (CO),
146.6, 142.42 (PhC±C), 138.3 (ArC(1)±O), 128.5, 128.2,
128.0, 127.9, 127.5, 127.1 (PhC±H), 109.0 (ArC(2)±C),
98.3 (ArC(3)H), 94.8 (O±CH2±O), 93.4 (ArC(5)H), 83.0
(ArC(4)H), 80.2 (C±OH), 76.6 (ArC(6)H), 65.2 (O±CH2),
14.8 (Me). m/z (FAB1) 470 (M1), 453 (M12OH), 386
(M123£CO). Found: M1 470.0818. C25H22CrO6 requires:
470.0821.
(^)-h6-[2-Formyl(ethoxymethoxy)benzene]tricarbonyl-
chromium(0) (29a). This complex was prepared from
h6-(ethoxymethoxybenzene)tricarbonylchromium(0) (8a,
0.369 g, 1.28 mmol) in ether (25 mL) with a DMF
(5 equiv., 0.53 mL, 6.40 mmol) quench. FCC (eluent: 50%
ether/hexane) gave the complex (29a) as bright red crystals
(0.332 g, 1.049 mmol, 82%), mp 76±788C. (Found: C,
49.55; H, 3.81. C13H12CrO6 requires: C, 49.38; H, 3.82%).
nmax (CHCl3)/cm21 1984vs, 1917vs, 1682s, 1265s. dH
(270 MHz) 10.03 (1H, s, CHO), 6.21 (1H, dd, Jˆ1.5,
6.4 Hz, ArC(3)H), 5.80 (1H, ddd, Jˆ1.5, 6.4, 6.9 Hz,
ArC(5)H), 5.40 (1H, d, Jˆ6.9 Hz, ArC(6)H), 5.28 (1H, d,
Jˆ7.2 Hz, O±CHH±O), 5.19 (1H, d, Jˆ7.2 Hz, O±CHH±
O), 4.98 (1H, t, Jˆ6.4 Hz, ArC(4)H), 3.76 (2H, q,
Jˆ7.1 Hz, O±CH2), 1.24 (3H, t, Jˆ7.1 Hz, Me); dC
(68 MHz) 230.7 (CO), 185.5 (CHO), 143.8 (ArC(1)±O),
(^)-h6-[2-(Diphenylhydroxymethyl)-4-triisopropylsiloxy-
methyl(ethoxymethoxy)benzene]tricarbonylchromium(0)
(30b). This complex was prepared from h6-[4-triisopropyl-
siloxymethyl(ethoxymethoxy)benzene]tricarbonylchro-
mium(0) (8b, 308 mg, 0.65 mmol) with a quench of
benzophenone (5 equiv., 594 mg, 3.24 mmol) in THF

I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
6133
(3 mL). The reaction was worked up with water (10 mL).
FCC (eluent: 10% ether/hexane) furnished the complex
(30b) as a bright yellow crystalline solid (390 mg,
0.55 mmol, 92%) mp 82±848C. (Found: C, 64.18; H, 6.87.
C35H44CrO7Si requires: C, 64.00; H, 6.75%). nmax (KBr)/
cm21 3555w, 3086w, 3063w, 3026w, 2943m, 2865m,
1958vs, 1882vs, 1460m, 1101s, 667s, 481m. dH
(270 MHz) 7.42±7.25 (10H, m, PhH), 5.67 (1H, dd, Jˆ
1.7, 6.9 Hz, ArC(5)H), 5.30 (1H, d, Jˆ6.9 Hz, ArC(6)H),
4.96 (1H, d, Jˆ7.2 Hz, O±CHH±O), 4.91 (1H, d, Jˆ1.7 Hz,
ArC(3)H), 4.83 (1H, d, Jˆ7.2 Hz, O±CHH±O), 4.64 (1H, s,
OH), 4.24 (2H, s, Ar±CH2), 3.34±3.25 (1H, m, O±CH2),
3.12±3.04 (1H, m, O±CH2), 1.06±0.93 (24H, m, TIPS, Me);
dC (68 MHz) 232.6 (CO), 146.8 (ArC(1)±O), 142.4
ArC(6)H), 4.94 (1H, d, Jˆ13.9 Hz, Ar±CH2), 4.73 (1H, d,
Jˆ13.9 Hz, Ar±CH2), 4.05±3.95 (2H, m, O±CH2), 3.67
(2H, t, Jˆ4.7 Hz, CH2±O), 3.40 (3H, s, OMe), 1.20±1.01
(21H, m, TIPS); dC (68 MHz) 231.4 (CO), 189.5 (CHO),
138.8 (ArC(1)±O), 108.9 (ArC(4)±CH2), 93.5 (ArC(3)±
CHO), 90.9 (ArC(5)H), 82.1 (ArC(2)H), 78.8 (ArC(6)H),
70.4 (CH2±O), 68.8 (O±CH2), 61.2(Ar±CH2), 59.9
(OMe), 18.0 (TIPS±Me), 11.9 (Si±CH). m/z(FAB1) 502
(M1), 367, 346, 329, 210, 52. Found: M1 502.1484.
C23H34CrO7Si requires: 502.1478.
Further elution gave the complex (32b) as a bright orange
crystalline solid (240 mg, 0.48 mmol, 72%) mp 42±448C.
(Found: C, 55.02; H, 6.99. C23H34CrO7Si requires: C, 54.96;
H, 6.82%). nmax (KBr)/cm21 2943m, 2866m, 1971vs, 1931s,
1891vs, 1666s, 1539m, 1463m, 1354m, 1239m, 1118s,
655s, 520w. dH (270 MHz) 10.07 (1H, s, CHO), 6.29 (1H,
d, Jˆ1.7 Hz, ArC(3)H), 5.97 (1H, dd, Jˆ1.7, 6.9 Hz,
ArC(5)H), 5.07 (1H, d, Jˆ6.9 Hz, ArC(6)H), 4.49 (1H, d,
Jˆ12.6 Hz, Ar±CH2), 4.42 (1H, d, Jˆ12.6 Hz, Ar±CH2),
4.21±4.03 (2H, m, O±CH2), 3.72±3.61 (2H, m, CH2±O),
3.41 (3H, s, OMe), 1.23±1.01 (21H, m, TIPS); dC (68 MHz)
230.8 (CO), 185.6 (CHO), 144.9 (ArC(1)±O), 104.0
(ArC(4)±CH2), 93.2 (ArC(3)H), 90.2 (ArC(5)H), 85.4
(ArC(2)±CHO), 72.7 (ArC(6)H), 70.3 (CH2±O), 68.9 (O±
CH2), 62.7 (Ar±CH2), 59.9 (OMe), 18.0 (TIPS±Me), 11.9
(Si±CH). m/z (FAB1) 503 (M11H), 446 (M122£CO), 418
(M123£CO), 390, 375, 359, 347, 277. Found: M1
502.1476. C23H34CrO7Si requires: 502.1478.
(Ph(C)±COH),
137.7
(Ph(C)±COH),
128.4±127.2
(Ph(C)H), 108.6 (ArC(4)±CH2), 102.1 (ArC(2)±COH),
96.7 (ArC(3)H), 93.5 (O±CH2±O), 92.8 (ArC(5)H), 80.4
(C±OH), 76.1 (ArC(6)H), 65.1 (O±CH2), 63.1 (Ar±CH2),
18.0 (TIPS±Me), 14.8 (Me), 11.9 (Si±CH). m/z (CI) 674
(M11NH4), 656 (M1), 639 (M11H2OH), 572
(M123£CO), 503 (6392Cr(CO)3), 483, 444, 271, 183,
105, 59, 52 (Cr). Found: M1 656.2272. C35H44CrO7Si
requires 656.2261.
(^)-h6-[2-(Di-4-methoxyphenylhydroxymethyl)(ethoxy-
methoxy)benzene]tricarbonylchromium(0) (31a). This
complex was prepared from h6-(ethoxymethoxy)benzene-
tricarbonylchromium(0) (8a, 0.369 g, 1.28 mmol) in ether
(25 mL) with a 4,40-dimethoxybenzophenone (5 equiv.,
1.239 g, 6.40 mmol) quench. FCC (eluent: 50% ether/
hexane) gave the complex (31a) as yellow crystals
(0.542 g, 1.022 mmol, 80%), mp 132±1348C. (Found: C,
61.03; H, 5.03. C27H26CrO8 requires: C, 61.13; H, 4.94%).
nmax (CHCl3)/cm21 3399 br, 1971vs, 1896vs, 1250s. dH
(270 MHz) 7.30±7.20 (4H, m, PhH), 6.80±6.87 (4H, t,
Jˆ8.7 Hz, PhH), 5.55 (1H, t, Jˆ6.3 Hz, ArC(5)H), 5.30
(1H, d, Jˆ6.3 Hz, ArC(3)H), 4.99 (1H, d, Jˆ7.4 Hz, O±
CHH±O), 4.86 (1H, d, Jˆ7.4 Hz, O±CHH±O), 4.77 (1H,
d, Jˆ6.3 Hz, ArC(6)H), 4.61 (1H, t, Jˆ6.3 Hz, ArC(4)H),
4.53 (1H, s, OH), 3.79 (6H, s, PhOMe), 3.37 (1H, m, O±
CH2), 3.17 (1H, m, O±CH2), 1.05 (3H, t, Jˆ7.2, Me); dC
(68 MHz) 232.7 (CO), 159.3, 158.8 (PhC±OMe), 138.7,
135.8 (PhC±C), 132.3 (ArC(1)±O), 129.7, 128.3, 127.8,
113.9, 113.7 (PhC±H), 109.6 (ArC(2)±C), 98.3
(ArC(3)H), 94.8 (O±CH2±O), 93.6 (ArC(5)H), 83.2
(ArC(4)H), 79.8 (C±OH), 77.0 (ArC(6)H), 65.2 (O±CH2),
55.6, 56.4 (Ph±OMe), 14.9 (Me). m/z (FAB1) 530 (M1),
513 (M12OH), 446 (M123£CO). Found: M1 530.1042.
C27H26CrO8 requires: 530.1033.
(1)-h6-[2-(Diphenylhydroxymethyl)-4-triisopropylsiloxy-
methyl(2-methoxyethoxy)benzene]tricarbonylchromium(0)
(33b). This complex was prepared from h6-[4-triisopropyl-
siloxymethyl(2-methoxyethoxy)benzene]tricarbonylchro-
mium(0) (9b, 308 mg, 0.65 mmol with a quench of
benzophenone (5 equiv., 594 mg, 3.24 mmol) in THF
(3 mL). The reaction was worked up with water (10 mL).
FCC (eluent: 10% ether/hexane) furnished the complex
(33b) as a bright yellow crystalline solid (301 mg,
0.47 mmol, 72%) mp 36±388C. (Found: C, 64.20; H, 6.58.
C35H44CrO7Si requires: C, 64.00; H, 6.75%). nmax (KBr)/
cm21 3490m, 3060w, 3026w, 2943s, 2865s, 1964vs,
1889vs, 1447s, 1240m, 1100s, 667s, 537m. dH
(270 MHz3) 7.37±7.23 (10H, m, PhH), 5.61 (1H, dd, Jˆ
1.7, 4.0 Hz, ArC(5)H), 5.27 (1H, d, Jˆ4.0 Hz, ArC(6)H),
4.86 (1H, d, Jˆ6.7 Hz, OH), 4.86 (1H, d, Jˆ1.7 Hz,
ArC(3)H), 4.27 (1H, d, Jˆ12.6 Hz, Ar±CH2±O), 4.21
(1H, d, Jˆ12.6 Hz, Ar±CH2), 3.95- 3.79 (2H, m, O±CH2),
3.47±3.28 (2H, m, CH2±O), 3,3 (3H, s, OMe), 1.19±0.84
(21H, m, TIPS); dC (68 MHz) 232.5 (CO), 152.2 (ArC(1)±
O), 147.4 (Ph(C)±COH), 137.4 (Ph(C)±COH), 128.4±
127.1 (Ph(C)H), 108.4 (ArC(4)±CH2), 101.9 (ArC(2)±
COH), 96.8 (ArC(3)H), 91.9 (ArC(5)H), 76.5 (C±OH),
72.8 (ArC(6)H), 69.7 (CH2±O), 68.7(O±CH2), 63.1 (Ar±
CH2), 58.9 (OMe), 18.0 (TIPS±Me), 11.9 (Si±CH). m/z
(CI) 674 (M11NH4), 639 (M11H±OH), 572
(M123£CO), 520 (M12Cr(CO)3), 503 (6392Cr(CO)3),
477, 429, 331, 301, 200. Found: M11NH4 674.2601.
C35H48CrNO7Si requires 674.2605.
(^)-h6-[2-Formyl-4-triisopropylsiloxymethyl(2-methoxy-
ethoxy)benzene]tricarbonylchromium(0) (32b). This
complex was prepared from h6-[4-triisopropylsiloxymethyl
(2-methoxyethoxy)benzene]tricarbonylchromium(0) (9b,
308 mg, 0.65 mmol) in ether (10 mL) with over night
DMF (1.7 equiv., 0.08 mL, 1.11 mmol) quench. The
reaction was worked up with water (10 mL). FCC (eluent:
20% ether/hexane) furnished the meta-substituted complex
(32c) as a red crystalline solid. (60 mg, 0.12 mmol, 18%),
mp 38±408C. nmax (KBr)/cm21 2944s, 2866s, 1971vs,
1888vs, 1687s, 1543s, 1276s, 1127s, 653s. dH (270 MHz)
9.81 (1H, s, CHO), 5.73 (1H, d, Jˆ7.2 Hz, ArC(5)H), 5.64
(1H, d, Jˆ2.2 Hz, ArC(2)H), 5.53 (1H, dd, Jˆ2.2, 7.2 Hz,
(1)-h6-[2-Formyl-4-triisopropylsiloxymethyl(methoxy-
ethoxymethoxy)benzene]tricarbonylchromium(0) (34b).
This complex was prepared from h6-[4-triisopropylsiloxy-

6134
I. K. Sebhat et al. / Tetrahedron 56 (2000) 6121±6134
methyl(methoxy-ethoxymethoxy)benzene]tricarbonylchro-
mium(0) (10b, 328 mg, 0.65 mmol) with a quench with
DMF (2 equiv., 0.10 mL, 1.30 mmol). FCC (eluent: 50%
ether/hexane) furnished the complex (34b) as a red oil
(254 mg, 0.46 mmol, 73%). (Found: C, 53.81, H, 6.78.
C24H36CrO8Si requires: C, 54.12; H, 6.81%). nmax (neat)/
cm21 2945s, 2868s, 1978vs, 1903vs, 1682s, 1466s, 1109s,
660s. dH (270 MHz) 10.03 (1H, s, CHO), 6.26 (1H, d,
Jˆ1.7 Hz, ArC(3)H), 5.95 (1H, dd, Jˆ1.7, 6.9 Hz,
ArC(S)H), 5.42 (1H, d, Jˆ6.9 Hz, ArC(6)H), 5.31 (1H, d,
Jˆ7.2 Hz, O±CHH±O), 5,22 (1H, d, Jˆ7.2 Hz, O±CHH±
O), 4.47 (1H, d, Jˆ12.6 Hz, Ar±CH2), 4.40 (1H, d,
Jˆ12.6 Hz, Ar±CH2), 3.88±3.83 (2H, M, O±CH2), 3.58±
3.53 (2H, m, CH2±O), 3.37 (3H, s, OMe), 1. 17±0.97 (21H,
m, TIPS); dC (68 MHz) 230.8 (CO), 185.6 (CHO), 143.1
(ArC(1)±O), 104.3 (ArC(4)±CH2), 94.7 (O±CH2±O), 93.4
(ArC(3)H), 89.9 (ArC(5)H), 85.2 (ArC(2)±CHO), 75.9
(ArC(6)H), 7±1.4 (CH2±O), 69.2 (O±CH2), 62.8 (Ar±
CH2), 59.1 (OMe), 18.0 (TIPS±Me), 11.9 (Si±CH). m/z
(CI) 550 (M11NH4), 533 (M11H), 504 (M1-CO), 448
(M123£CO), 414, 280, 182. Found: M1 532.1584.
C24H36CrO8Si requires: 532.1585.
References
Â
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(1)-h6-[2-Trimethylsilyl-N-Boc-aniline)tricarbonylchro-
mium(0) (35a). This complex was prepared from
h6-(N-Boc-aniline)tricarbonylchromium(0) (11a, 0.32 g,
1.00 mmol) with
a
chlorotrimethylsilane (5 equiv.,
10. Gould, S. J.; Eisenberg, R. L. J. Org. Chem. 1991, 56, 6666.
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0.63 mL, 5.00 mmol) quench. FCC (eluent: 2±5% ether/
hexane) and recrystallisation (from DCM/hexane) furnished
the complex (35a) as bright yellow crystals (0.24 g,
0.77 mmol, 77%), mp 83±858C. nmax (Nujol)/cm21 3456w
(NH), 2924vs, 1948vs, 1878vs, 1749s, 1456s, 629s. dH
(270 MHz) 6.03±6.00 (2H, m, NH, ArC(5)H), 5.50 (1H,
dd, Jˆ1.2, 6.5 Hz, ArC(6)H), 4.90 (1H, t, Jˆ6.2 Hz,
ArC(4)H), 1.49 (9H, s, CMe3), 0.40 (9H, s, TMS); dC
(75 MHz) 152.6 (COO), 121.8 (ArC(1)±N), 100.2
(ArC(3)H), 96.2 (ArC(5)H), 89.4 (ArC(2)±Si), 86.8
(ArC(4)H), 85.8 (ArC(6)H), 8.19 (CMe3), 28.1 (Me), 20.2
(TMS). m/z(CI) 419 (M1186.8 (ArC(4)H), 85.8 (ArC(6)H),
8.19 (CMe3), 28.1 (Me), 20.2 (TMS). m/z(CI) 419
(M11NH4), 402(M11H), 346 (40222£CO), 328
(M12OtBu, M12TMS), 227 (3282TMS, 3282OtBu),
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20. Schaper, U. A. Synthesis 1981, 10, 794.
193 (3281H2Cr(CO)3). Found: M1
402.0832.
C17H24CrNO5Si requires 402.0829.
21. Gonzalez, A. G.; Rosa, R. D. L.; Trujillo, J. M. Tetrahedron
1986, 42, 3899.
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Acknowledgements
We thank the Engineering and Physical Sciences Research
Council and the Government of Singapore for ®nancial
support.
26. Bennett, F.; Knight, D. W.; Fenton, G. J. J. Chem. Soc., Perkin
Trans. 1 1991, 1543.