Chemo- and diastereoselective Bi(OTf)3-catalyzed benzylation of silyl nucleophiles

Article abstract of DOI:10.1016/j.tetlet.2007.12.092

The direct alkylation of silyl enol ethers with para-methoxybenzylic alcohols or their corresponding acetates was efficiently catalyzed by Bi(OTf)₃ in CH₃NO₂ as the solvent. The reaction provided the α-benzylated carbonyl

Full text of DOI:10.1016/j.tetlet.2007.12.092

Available online at www.sciencedirect.com
Tetrahedron Letters 49 (2008) 1305–1309
Chemo- and diastereoselective Bi(OTf)3-catalyzed benzylation
of silyl nucleophiles
Philipp Rubenbauer, Thorsten Bach *
Lehrstuhl fu¨r Organische Chemie I, Technische Universita¨t Mu¨nchen, Lichtenbergstr. 4, 85747 Garching, Germany
Received 6 November 2007; revised 11 December 2007; accepted 19 December 2007
Abstract
The direct alkylation of silyl enol ethers with para-methoxybenzylic alcohols or their corresponding acetates was efficiently catalyzed
by Bi(OTf)3 in CH3NO2 as the solvent. The reaction provided the a-benzylated carbonyl compounds in high yields after short reaction
times using 1–2.5 mol % of the catalyst. Benzylic acetates other than para-methoxybenzylic acetates also underwent the reaction. High
facial diastereoselectivities were observed with acetates derived from chiral a-branched para-methoxybenzylic alcohols. In addition, a
catalytic reduction with Et3SiH as the reducing agent is reported.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Bi catalysis; Benzylic alcohols; Silyl enol ether; Facial diastereoselectivity; Triethylsilane
The counterpart of the conventional enolate alkylation
under basic conditions is the acid-promoted alkylation of
silyl enol ethers.1,2 The latter reaction is most frequently
applied to substrates which allow for a facile SN1-type sub-
stitution. Important examples include tert-alkylation3 and
benzylation4 reactions, which have been extensively studied
in recent years.2 Our interest in the benzylation and more
specifically in the methoxybenzylation of silyl enol ethers
stems from previous work, in which we studied the Frie-
del–Crafts alkylation of various arenes with chiral a-
branched para-methoxybenzylic alcohols.5 We envisioned
that silyl enol ethers could serve as possible nucleophiles
for related reactions under catalytic reaction conditions.
It turned out that bismuth tris(trifluoromethanesulfonate)
(Bi(OTf)3) is a very efficient catalyst6 for these reactions
and we report in this Letter on our preliminary results in
this area.
by Rueping et al.7,8 Given the high temperatures (55–
100 °C) required in these benzylation reactions, it was a
pleasant surprise to note that the methoxybenzylation of
silyl enol ethers can be achieved at ambient temperature
in nitromethane as the solvent (Scheme 1, Table 1).
Sterically more congested para-methoxyphenyl-1-etha-
nol (1) was used in a first set of experiments as the alkyl-
ating agent (instead of the parent methoxybenzylalcohol)
to mimic the situation in a-branched para-methoxybenzylic
alcohols (vide infra). Silyl enol ethers 2 were prepared
according to known procedures.9 Reactions proceeded
smoothly and provided the desired products10 in high
yields (73–96%, entries 1–8). The only exception was
observed with the a,a0-disubstituted silyl ketene acetal 2i
(entry 9), which gave only a mediocre result. All reactions
OH
1 mol-% Bi(OTf)3
r.t. (CH3NO2)
The suitability of Bi(OTf)3 to activate benzylated alco-
hols for nucleophilic attack has been demonstrated earlier
O
OSiMe3
X
R
X
+
see table 1
R
R1
R1
MeO
MeO
*
1
2
3
Corresponding author. Tel.: +49 (0)89 289 13330; fax: +49 (0)89 289
13315.
Scheme 1.
E-mail address: thorsten.bach@ch.tum.de (T. Bach).
0040-4039/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.12.092

1306
P. Rubenbauer, T. Bach / Tetrahedron Letters 49 (2008) 1305–1309
Table 1
Reaction of alcohol 1 with different silyl enol ethers 2 (cf. Scheme 1)
Entry
1
Enol ether
OSiMe3
Product
MeO
Time (h)
4
Yielda (%)
89b
O
O
Ph
3a
2a
Ph
OSiMe3
Ph
2
3
4
5
6
7
3
5
4
4
2
1
76
Ph
3b11
2b
MeO
O
O
O
O
OSiMe3
tBu
tBu
79
2c
3c
MeO
MeO
MeO
MeO
MeO
OSiMe3
StBu
StBu
77
2d
3d
OSiMe3
OMe
73
OMe
2e
3e
OSiMe3
2f
OSiMe3
91c
96c
3f
O
O
2g
3g
OSiMe3
8
1
96c
2h
3h
MeO
MeO
MeO
OSiMe3
CO2Me
9
0.5
48
3i
2i
a
Yield of isolated product after column chromatography.
Diasteromeric ratio (1H NMR) dr = 69:31.
Diasteromeric ratio (1H NMR) dr = 50:50.
b
c
O
2.5 mol-% Bi(OTf)3
were run at room temperature with the initially clear solu-
tion becoming slightly turbid after ca. 15 min.
2f, rt, 15 h (CH3NO2)
OH
It was shown in a second set of experiments (Scheme 2)
with silyl enol ether 2f as the nucleophile that other meth-
oxybenzylic alcohols can be equally well employed as elec-
trophile precursors. The parent alcohol 4 yielded the
substitution product ketone 512 and ortho-methoxy-
phenyl-1-ethanol (6) gave with the same silyl nucleophile
product 7 (Scheme 2). Yields were high but a larger amount
of Bi(OTf)3 had to be employed for full conversion and
reaction times were required to be longer.
81%
MeO
MeO
4
5
2.5 mol-% Bi(OTf)3
2f, rt, 10 h (CH3NO2)
O
OMe OH
OMe
81%
6
7
Scheme 2.

P. Rubenbauer, T. Bach / Tetrahedron Letters 49 (2008) 1305–1309
1307
2.5 mol-% Bi(OTf)3
in these transformations are, of course, dependent on the
substitution pattern at the stereogenic center.5
O
OAc
2f, rt, 4 h (CH3NO2)
The nitro-substituted substrate 10 delivered ketone anti-
11 with almost perfect stereoselectivity while the selectivity
in the reaction of cyanoacetate 12 (to ketone anti-13) was
lower. Phosphonate 14 delivered a major diastereoisomer
to which the syn-configuration syn-15 was assigned. This
and the other assignments are based on the close analogy
to the previously studied diastereoselective arylation reac-
tions.5b In the case of product syn-15, the configuration
91%
MeO
MeO
MeO
MeO
8
3f
O
2.5 mol-% Bi(OTf)3
O
2f, rt, 2 h (CH3NO2)
2
86%
9
5
Scheme 3.
1
assignment was further supported by H and 13C NMR
data.13 Aldol-derived acetate 16 gave product anti-17 with
excellent diastereoselectivity (dr = 94:6). In all the cases,
1–5 mol % of the catalyst was required to achieve full con-
version. The substrate dr is given in brackets for every ace-
tate, which was used (Scheme 4). As expected for SN1 type
reactions, the diastereomeric composition of the starting
materials did not influence the product diastereoselectivity.
The reactions proceeded in a stereoconvergent fashion.
Other benzyl acetates but para-methoxybenzyl were
identified as suitable benzylation reagents in combination
with Bi(OTf)3. While the corresponding alcohols, from
which acetates 18 and 20 are derived, did not undergo a
benzylation reaction, the corresponding acetates did. The
product ketones 19 and 21 were obtained in very good
yields (Scheme 5). Benzylic alcohols without an electron
releasing substituent at the phenyl ring, for example, the
parent benzylic alcohol (BnOH), or their acetates did not
react.
Given the mechanistic similarity of the SN1-type substi-
tution by silyl enol ethers and the acid-catalyzed reduction
by hydrosilanes,14 we briefly looked into a possible
Bi(OTf)3-catalyzed reduction of para-methoxybenzylic
alcohols.15 We were pleased to find that the reactions of
this type proceeded smoothly employing Et3SiH16 as the
hydride source (Scheme 6). Benzylic alcohol 1 was con-
verted into the corresponding hydrocarbon 2217 using
2.5 mol % Bi(OTf)3. The aldol addition product 23 was
readily reduced to para-methoxyphenylpropionate 2418
employing as little as 1 mol % of the catalyst.
Further, electrophile variation revealed that acetate 8 of
alcohol 1 was also an appropriate starting material for the
alkylation reaction delivering ketone 3f in 91% yield
(Scheme 3). In the experiments with alcohol 4 (Scheme 2),
it appeared as if the corresponding dibenzylether 9 was
formed as side product/intermediate, which was consumed
in the further course of the reaction. Indeed, we could show
that this ether is an equally efficient starting material in the
methoxybenzylation providing ketone 5 in 86% yield.
While dibenzylether formation is reversible, crossover
experiments clearly established that the formation of prod-
ucts 3 is irreversible. Stirring of ketone 3c or 3d in the pres-
ence of catalytic quantities of Bi(OTf)3 and of excess silyl
enol ether 2f, for example, did not give a hint for the for-
mation of ketone 3f.
Various precursors were screened to optimize the reac-
tions of para-methoxybenzylic alcohols with a stereogenic
center in a-position.5b Acetates proved to be the best choice
providing the desired ketones in high yield with good facial
diastereoselectivity (Scheme 4).13 The selectivities achieved
O
2.5 mol-% Bi(OTf)3
OAc
tBu
NO2
2b, rt, 16 h (CH3NO2)
NO2
84% dr = 95/5
MeO
MeO
10 (dr = 65/35)
anti-11
O
2.5 mol-% Bi(OTf)3
OAc
CN
Ph
CN
2c, rt, 20 h (CH3NO2)
In summary, we have shown that Bi(OTf)3 can be an
efficient catalyst to promote C–C bond forming reactions
between methoxybenzylic alcohols and silyl enol ethers.
The reactions proceed under mild conditions in very good
yields. Related cation precursors, such as acetates and
89% dr = 81/19
MeO
MeO
12 (dr = 60/40)
anti-13
O
5 mol-% Bi(OTf)3
OAc
tBu
PO(OEt)2
2b, rt, 16 h (CH3NO2)
PO(OEt)2
2.5 mol-% Bi(OTf)3
O
OAc
83% dr = 93/7
MeO
2f, rt, 1 h (CH3NO2)
MeO
74%
14 (dr = 75/25)
syn-15
18
19
O
1 mol-% Bi(OTf)3
OAc
tBu
COOMe
2.5 mol-% Bi(OTf)3
2f, rt, 1 h (CH3NO2)
OAc
2b, rt, 5 h (CH3NO2)
COOMe
O
78% dr = 94/6
88%
MeO
MeO
16 (dr = 52/48)
anti-17
20
21
Scheme 4.
Scheme 5.

1308
P. Rubenbauer, T. Bach / Tetrahedron Letters 49 (2008) 1305–1309
9. 2a, 2b, 2d, 2e, 2i: (a) Bach, T.; Jo¨dicke, K. Chem. Ber. 1993, 126,
2.5 mol-% Bi(OTf)3
Et3SiH, rt, 4 h
(CH3NO2)
OH
2457–2466; 2c, 2f, 2g, 2h: (b) Cazeau, P.; Duboudin, F.; Moulines, F.;
Babot, O.; Dunogues, J. Tetrahedron 1987, 43, 2075–2088.
10. General procedure: para-methoxyphenyl-1-ethanol (1, 76 mg,
0.5 mmol) and a silyl enol ether 2 (1.0 mmol) were dissolved in
nitromethane (2 mL). At ambient temperature Bi(OTf)3ꢀxH2O
(1 < x < 4)6a (8 mg, 12.5 lmol) was added in one portion and the
solution was stirred for the indicated time. The reaction was quenched
by the addition of EtOAc/water (10:10 mL) and the aqueous layer
was extracted with ethyl acetate (2 ꢁ 20 mL). The combined organic
layers were washed with water (20 mL) and brine (20 mL), dried over
Na2SO4 and the solvent was removed under reduced pressure. The
crude product was purified by flash chromatography (cyclohexane/
ethyl acetate 40:1). Analytical data for some selected compounds:
Compound 3c: Rf: 0.11 (cyclohexane/EtOAc 40:1); IR (film):
~m ¼ 2964 cmꢂ1 ðsÞ, 2834 (m), 1706 (vs), 1612 (m), 1513 (vs), 1464
(m), 1249 (vs), 1178 (m), 1039 (s), 829 (m). 1H NMR (360 MHz,
CDCl3): d = 1.05 (s, 9H), 1.21 (d, 3J = 7.0 Hz, 3H), 2.66 (dd,
2J = 17.1 Hz, 3J = 7.7 Hz, 1H), 2.73 (dd, 2J = 17.1 Hz, 3J = 6.3 Hz,
1H), 3.33 (pseudo sextet, 3J ffi 7.0 Hz, 1H), 3.78 (s, 3H), 6.82 (d,
3J = 8.7 Hz, 2H), 7.13 (d, 3J = 8.7 Hz, 2H). 13C NMR (90.6 MHz,
CDCl3): d = 21.9 (q), 26.3 (q), 34.3 (d), 44.2 (s), 45.7 (t), 55.4 (q),
113.9 (d), 127.9 (d), 139.1 (s), 158.0 (s), 214.5 (s). HRMS (C15H22O2):
calcd.: 234.1620, found: 234.1616.
MeO
82%
MeO
1
22
24
1 mol-% Bi(OTf)3
Et3SiH, rt, 12 h
(CH3NO2)
OH
CO2Me
CO2Me
MeO
75%
MeO
23 (dr = 52/48)
Scheme 6.
ethers, can be employed and a diastereoselective reaction is
feasible with appropriately substituted substrates. In addi-
tion, C–H bond formation is possible under similar condi-
tions using Et3SiH as the reducing agent.
Acknowledgments
Compound ꢂ31e: Rf: 0.09 (cyclohexane/EtOAc 40:1); IR (film):
This work was supported by the Deutsche Forschungs-
gemeinschaft, by the graduate college NanoCat (scholarship
to P.R.) and by the Fonds der Chemischen Industrie.
~
m ¼ 2972 cm ðsÞ, 2835 (m), 1731 (vs), 1611 (w), 1513 (vs), 1461
(m), 1249 (vs), 1133 (s), 1036 (m), 833 (m). 1H NMR (360 MHz,
CDCl3): d = 1.05 (s, 3H), 1.10 (s, 3H), 1.22 (d, 3J = 7.2 Hz, 3H), 3.11
3
(q, J = 7.2 Hz, 1H), 3.64 (s, 3H), 3.79 (s, 3H), 6.81 (d, 3J = 8.7 Hz,
2H), 7.08 (d, 3J = 8.7 Hz, 2H). 13C NMR (90.6 MHz, CDCl3):
d = 16.2 (q), 20.9 (q), 23.9 (q), 45.9 (s), 46.7 (d), 51.7 (q), 55.3 (q),
113.3 (d), 130.1 (d), 134.7 (s), 158.4 (s), 178.4 (s). HRMS (C14H20O3):
calcd.: 236.1412, found: 236.1412.
References and notes
1. Review: Reetz, M. T. Angew. Chem., Int. Ed. 1982, 21, 96–108.
2. For a recent review on silyl enol ether chemistry, see: Kobayashi, S.;
Manabe, K.; Ishitani, H.; Matsuo, J.-I. In Science of Synthesis.
Houben-Weyl Methods of Molecular Transformations; Fleming, I.,
Ed.; Thieme: Stuttgart, 2002; Vol. 4, pp 317–369.
3. (a) Chan, T. H.; Paterson, I.; Pinsonnault, J. Tetrahedron Lett. 1977,
18, 4183–4186; (b) Reetz, M. T.; Maier, W. F. Angew. Chem., Int. Ed.
1978, 17, 48–49; (c) Reetz, M. T.; Maier, W. F.; Chatziiosifidis, I.;
Giannis, A.; Heimbach, H.; Lo¨we, U. Chem. Ber. 1980, 113, 3741–
3757.
Compounds 3h (50:50 mixture of diastereoisomers): Rf: 0.09 (cyclo-
hexane/EtOAc 40:1); IR (film): ~m ¼ 2935 cmꢂ1 (s), 2835 (m), 1703 (vs),
1610 (w), 1513 (vs), 1455 (m), 1247 (vs), 1180 (s), 1031 (m), 832 (s). 1H
NMR (360 MHz, CDCl3): d = 0.87 (s, 1.5H), 0.92 (s, 1.5H), 1.10 (d,
3J = 7.2 Hz, 1.5H), 1.23 (d, 3J = 7.1 Hz, 1.5H), 1.20–1.28 (m, 0.5H),
1.45–1.51 (m, 0.5H), 1.60–1.71 (m, 2H), 1.74–1.87 (m, 2H), 1.97–2.10
(m, 1H), 2.33–2.43 (m, 1H), 2.49–2.60 (m, 1H), 3.36–3.45 (m, 1H),
3.77 (s, 1.5H), 3.80 (s, 1.5H), 6.79 (d, 3J = 8.6 Hz, 1H), 6.84 (d,
3J = 8.6 Hz, 1H), 7.05 (d, 3J = 8.6 Hz, 1H), 7.13 (d, 3J = 8.6 Hz, 1H).
13C NMR (90.6 MHz, CDCl3): d = 15.8 (q), 16.1 (q), 17.9 (q), 20.7 (t),
21.2 (t), 22.2 (q), 26.6 (t), 28.2 (t), 34.2 (t), 38.1 (t), 39.3 (t), 39.5 (t),
40.4 (d), 42.5 (d), 52.4 (s), 52.8 (s), 55.3 (q), 55.4 (q), 113.3 (d), 113.3
(d), 129.9 (d), 130.3 (d), 134.0 (s), 135.0 (s), 158.2 (s), 158.4 (s), 215.5
(s), 216.2 (s). Anal. Calcd for C16H22O2: C, 78.01; H, 9.00. Found: C,
78.13; H, 9.36.
4. (a) Paterson, I. Tetrahedron Lett. 1979, 20, 1519–1520; (b) Reetz, M.
T.; Huttenhain, S.; Walz, P.; Lo¨we, U. Tetrahedron Lett. 1979, 20,
¨
4971–4974; (c) Reetz, M. T.; Walz, P.; Hubner, F.; Huttenhain, S. H.;
¨
¨
Heimbach, H.; Schwellnus, K. Chem. Ber. 1984, 117, 322–335; (d)
Mukaiyama, T.; Matsui, S.; Homma, K.; Kobayashi, S. Bull. Chem.
Soc. Jpn. 1990, 63, 2687–2690; (e) Grieco, P. A.; Handy, S. T.
Tetrahedron Lett. 1997, 38, 2645–2648.
11. Singhal, N.; Koner, A. L.; Mal, P.; Venugopalan, P.; Nau, W. M.;
Moorthy, J. N. J. Am. Chem. Soc. 2005, 127, 14375–14382.
12. Wu, Y.; Li, Y.; Wu, Y.-L. Helv. Chim. Acta 2001, 84, 163–171.
13. Analytical data of compound anti-13: Rf: 0.37 (cyclohexane/EtOAc
3:1); IR (film): ~m ¼ 2936 cmꢂ1 ðsÞ, 2836 (w), 1687 (vs), 1612 (m), 1514
(vs), 1448 (m), 1252 (vs), 1180 (m), 1033 (m), 831 (w). 1H NMR
(360 MHz, CDCl3): d = 1.23 (d, 3J = 7.1 Hz, 3H), 2.94 (pseudo
quintet, 3J ffi 7.1 Hz, 1H), 3.50–3.62 (m, 3H), 3.76 (s, 3H), 6.83 (d,
5. (a) Stadler, D.; Muhlthau, F.; Rubenbauer, P.; Herdtweck, E.; Bach,
¨
T. Synlett 2006, 2573–2576; (b) Stadler, D.; Bach, T. Chem. Asian J.
2008, in press; doi:10.1002/asia.200700241; see also: (c) Mu¨hlthau, F.;
Stadler, D.; Goeppert, A.; Olah, G. A.; Prakash, G. K. S.; Bach, T. J.
Am. Chem. Soc. 2006, 128, 9668–9675.
6. Reviews: (a) Gaspard-Iloughmane, H.; Le Roux, C. Eur. J. Org.
Chem. 2004, 2517–2532; (b) Leonard, N. M.; Wieland, L. C.; Mohan,
R. S. Tetrahedron 2002, 58, 8373–8397.
3
3J = 8.7 Hz, 2H), 7.18 (d, J = 8.7 Hz, 2H), 7.42–7.46 (m, 2H), 7.53–
7.57 (m, 1H), 7.89–7.92 (m, 2H). 13C NMR (90.6 MHz, CDCl3):
d = 16.7 (q), 32.0 (d), 42.3 (t), 43.3 (d), 55.4 (q), 114.3 (d), 122.2 (s),
128.2 (d), 128.8 (d), 128.9 (d), 132.3 (s), 133.4 (d), 136.9 (s), 159.0 (s),
197.3 (s). Anal. Calcd for C19H19NO2: C, 77.79; H, 6.53; N, 4.77.
Found: C, 77.86; H, 6.44; N, 4.68.
Analytical data of compound syn-15: Rf: 0.39 (EtOAc); IR (film):
~m ¼ 3462 cmꢂ1 ðbrÞ, 2980 (s), 2836 (w), 2360 (w), 1682 (s), 1581 (m),
1514 (vs), 1391 (s), 1251 (s), 1029 (m), 957 (m), 836 (w). 1H NMR
(360 MHz, CDCl3): d = 1.15–1.32 (m, 9H), 2.18 (dqd,
3JHP = 21.5 Hz, 3J = 7.4 Hz, 3J = 3.4 Hz, 1H), 3.45–3.56 (m, 2H),
3.75 (s, 3H), 3.82–3.94 (m, 1H), 3.99–4.12 (m, 4H), 6.79 (d,
7. (a) Rueping, M.; Nachtsheim, B. J.; Ieawsuwan, W. Adv. Synth.
Catal. 2006, 348, 1033–1037; (b) Rueping, M.; Nachtsheim, B. J.;
Kuenkel, A. Org. Lett. 2007, 9, 825–828.
8. For related work, see: (a) Rubin, M.; Gevorgyan, V. Org. Lett. 2001,
3, 2705–2707; (b) Baba, A.; Yasuda, M.; Saito, T.; Ueba, M. Angew.
Chem., Int. Ed. 2005, 43, 1414–1416; (c) De, S. K.; Gibbs, R. A.
Tetrahedron Lett. 2005, 46, 8345–8350; (d) Shibasaki, M.; Qin, H.;
Yamagiwa, N.; Matsunaga, S. Angew. Chem., Int. Ed. 2007, 46, 409–
413; (e) Ishii, K.; Noji, M.; Konno, Y. J. Org. Chem. 2007, 72, 5161–
5167; (f) Nadeau, E.; Ollevier, T. Org. Biomol. Chem. 2007, 5,
3126–3134.

P. Rubenbauer, T. Bach / Tetrahedron Letters 49 (2008) 1305–1309
1309
3
3J = 8.7 Hz, 2H), 7.17 (d, J = 8.7 Hz, 2H), 7.41–7.45 (m, 2H), 7.50–
G.; Dittman, W. R.; Silverman, S. B. J. Org. Chem. 1978, 43, 374–375;
(c) Larsen, J. W.; Chang, L. W. J. Org. Chem. 1979, 44, 1168–1170;
(d) Orfanopoulos, M.; Smonou, I. Synth. Commun. 1988, 18, 833–839;
(e) Yato, M.; Homma, K.; Ishida, A. Heterocycles 1995, 41, 17–20.
15. Recent work on acid-catalyzed hydrosilane reductions: (a) Ishida,
J.-y.; Suzuki, H.; Komatsu, N. Tetrahedron Lett. 1997, 38, 7219–7222;
(b) Gevorgyan, V.; Yamamoto, Y.; Liu, J.-X.; Rubin, M.; Benson, S.
Tetrahedron Lett. 1999, 40, 8919–8922; (c) Gevorgyan, V.; Yamam-
oto, Y.; Rubin, M.; Benson, S.; Liu, J.-X. J. Org. Chem. 2000, 65,
6179–6186; (d) Baba, A.; Yasuda, M.; Onishi, Y.; Ueba, M.; Miyai, T.
J. Org. Chem. 2001, 66, 7741–7744; (e) Nagayama, S.; Mizutani, K.;
Hiroi, R.; Miyoshi, N.; Wada, M. Chem. Lett. 2002, 248–250.
16. Fry, J. L. In Handbook of Reagents for Organic Synthesis: Oxidizing
and Reducing Agents; Burke, S. D., Danheiser, R. L., Eds.; Wiley:
Chichester, 1999; pp 479–482.
7.55 (m, 1H), 7.94–7.97 (m, 2H). 13C NMR (90.6 MHz, CDCl3):
2
3
d = 10.1 (dq, JCP = 3.8 Hz), 16.5 (dq, JCP = 5.9), 16.6 (dq,
1
2
3JCP = 5.6 Hz), 37.2 (dd, JCP = 137 Hz), 39.2 (dt, JCP = 1.9), 39.4
3
2
(dd, JCP = 1.8), 55.3 (q), 61.6 (dt, JCP = 7.1 Hz), 61.8 (dt,
2JCP = 7.0 Hz), 113.8 (d), 128.3 (d), 128.6 (d), 129.2 (d), 133.0 (d),
134.3 (d, JCP = 13.9 Hz), 137.3 (s), 158.4 (s), 198.9 (s). Anal. Calcd
for C22H29O5P: C, 65.33; H, 7.23. Found: C, 64.91; H, 7.06.
Configuration assignment by 1H and 13C NMR data. 3J(P–
Car) = 13.8 Hz ()anti-periplanar); 3J(P–C1) = 1.9 Hz ()syn-clinal);
3J(H2–H3) = 3.4 Hz ()syn-clinal).
3
Ph
C1
1
O
Me
Car
2
3
PO(OEt)2
(EtO)2OP
H2
OMe
H3
17. Chauhan, B. P. S.; Rathore, J. S.; Bandoo, T. J. Am. Chem. Soc. 2004,
126, 8493–8500.
18. Orfanopoulos, M.; Smonou, I. Synth. Commun. 1990, 20, 1387–
1397.
MeO
syn-15
15
14. (a) Fry, J. L.; Adlington, M. G.; Orfanopoulos, M. Tetrahedron Lett.
1976, 17, 2955–2958; (b) Fry, J. L.; Orfanopoulos, M.; Adlington, M.