Chiral P,O-ligands derived from N,O-phenylene prolinols for palladium-catalyzed asymmetric allylic alkylation

Article abstract of DOI:10.1016/j.tetlet.2007.01.057

CuI-catalyzed N,O-arylation of (S)-prolinols and 1-bromo-2-iodobenzene afforded cyclic N,O-(1,2-phenylene)prolinols, and subsequent ortho-lithiation and phosphination provided a new type of chiral P,O-ligands. Their palladium-complex-catalyzed asymmetric

Full text of DOI:10.1016/j.tetlet.2007.01.057

Tetrahedron Letters 48 (2007) 1703–1706
Chiral P,O-ligands derived from N,O-phenylene prolinols
for palladium-catalyzed asymmetric allylic alkylation
Biao Jiang* and Zuo-Gang Huang
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China
Received 23 November 2006; revised 9 January 2007; accepted 11 January 2007
Available online 14 January 2007
Abstract—CuI-catalyzed N,O-arylation of (S)-prolinols and 1-bromo-2-iodobenzene afforded cyclic N,O-(1,2-phenylene)prolinols,
and subsequent ortho-lithiation and phosphination provided a new type of chiral P,O-ligands. Their palladium-complex-catalyzed
asymmetric allylic alkylation of dimethyl malonate with 1,3-diphenyl 2-propenyl acetate gave high yields and good
enantioselectivities.
Ó 2007 Elsevier Ltd. All rights reserved.
The development of effective and versatile chiral P,N-
ligands with sterically and electronically unsymmetric
nature for transition metal catalysis has been a fruitful
endeavor,1 while the exploration for chiral P,O-ligands
has received much less attention.2 The oxygen function-
ality in a P,O-ligand was often regarded as the spectator
or a hemilabile coordinating site.3 For example, CAMP
1, MOP 2 and semi-ESPHOS 3 were used as chiral
mono-phosphine ligands with the methoxy groups being
nonchelating bystanders.4 In particular, X-ray studies
revealed that the palladium-complex of MOP-type
ligands showed unique C–Pd r-bonding, g2-binding,
or diene-bridging modes rather than the P,O-bidentate
coordination.5
Exceptionally, some mixed phosphine–phosphine oxi-
des6 and phosphinocarboxylic acids7 as ligands were
reported working in P,O-chelating mode. A few other
types of hemilabile bidentate P,O-ligands were also
documented. Examples are (S)-prolinol-derived amido-
mono-phosphine ligand 4 for a Rh-catalyzed addition
reaction,8 ligand 5 with a chiral amine auxiliary for a
Pd–catalyzed allylic alkylation,9 and semi-DuPHOS-
type ligand 6 for a Ni-catalyzed hydrovinylation.10
Recently, we reported an interesting compound of the
N,O-(1,2-phenylene)prolinol structure.11 We wonder
that ortho-lithiation of this compound, followed by
phosphination, would produce a chiral P,O-ligand for
asymmetric catalysis (Scheme 1). Our interest in (S)-
prolinol-derived chiral ligands promoted us to try the
CuI-catalyzed coupling of (S)-prolinols with 1-bromo-
2-iodobenzene.12 However, an unexpected intramolecu-
lar N,O-arylation was observed in addition to the
normal N-arylation (Scheme 2).13
MeO
MeO
N
OMe
PPh2
P
P
N
Me
Ar
1
2
3
6
Aux ∗
O
The results are shown in Table 1. In the presence of
2.5 mol % CuI and 2 equiv of NaOH, mixing of 7a
O
HN
O
N
PPh2
P
R
O
PPh2
4
5
N
N
N
Ph2PCl
BuLi
O
O
Li
O
PPh2
*
Corresponding author. Fax: +86 21 64166128; e-mail: jiangb@
mail.sioc.ac.cn
Scheme 1.
0040-4039/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.01.057

1704
B. Jiang, Z.-G. Huang / Tetrahedron Letters 48 (2007) 1703–1706
R
R
OH
Br
substitution of 1,3-diphenyl-2-propenyl acetates 12 with
13 in the presence of BSA/LiOAc.18 The details are
shown in Table 2.19 It is noteworthy that comparable re-
sults (quantitative yields and 56–58% ees) were obtained
in THF regardless of 2:1 or 4:1 ratios for the phosphine
to the dimeric palladium source, albeit reaction under
the latter conditions was slightly accelerated (entries 1
and 2). It is probable that the catalyst formed in situ
worked in a 1:1 bidentate P,O-ligand to palladium coor-
dination mode. Thus, a 1.5:1 ratio was used in the rest of
our study. The reaction carried out in CH2Cl2 gave 99%
yield with somewhat lowered 51% ee (entry 3). Inferior
results were obtained in PhMe and MeCN (entries 4
and 5). Much rapid conversion was observed in ether,
but the enantioselectivity was only 41% ee (entry 6).
The optical yield was increased to 66% ee after an 8 h
reaction time at 0 °C (entry 7). Switching the ligand to
11b, a quantitative yield and 83% ee for 14 were attained
in 3 h at rt, and it took 48 h to achieve 93% yield with
90% ee in THF at 0 °C (entries 8 and 9).
R
O
R
R
OH
I
CuI (2.5%)
N
N
NaOH (2 eq)
+
R
+
N
-PrOH, 90 oC
Br
H
i
8
7a, R = H 7b, R = Me
7c, R = Et 7d, R = Ph
9a, b, c, d
10a, b, c
Scheme 2.
Table 1. CuI-catalyzed N-arylation and N,O-arylation
Entry Prolinol Time (h) Yield of 9a (%) Yield of 10a (%)
1
2
3b
4
5
6
7
8
7a
7a
7a
7b
7c
7c
7d
7d
12
24
12
24
24
50
3
23
5
62
78
13
31
57
36
50
—
60
75
3
c
25
None
None
20
a Isolated yields.
b NaOH (1 equiv).
All products are determined as (R)-configuration by
optical rotation measurement and chiral HPLC analy-
sis.20 On the basis of this output, a plausible mechanism
is proposed (Scheme 4). The P,O-ligand 11b has a rela-
tively rigid conformation. Upon analysis of the stereo-
electronics, the phenolic ether oxygen has two
discriminable lone pairs of electrons. The axial-oriented
lone pair tends to be in conjunction with the benzene
c Debromation occurred.
and 8 in i-PrOH with heating for 12 h afforded the nor-
mal N-arylation product 9a in 23% yield along with 62%
yield of a cyclic compound 10a (entry 1).14 As expected,
the yield of 10a was increased after longer reaction time,
while a shorter duration and using less base decreased
the N,O-arylation (entries 2 and 3). The N,O-arylation
product 10b was obtained in 31% yield (entry 4). Despite
the hindrance of cyclization to 10c, a 25% yield could be
attained with prolonged reaction time, albeit debroma-
tion occurred in the meantime (entries 5 and 6). The
N-arylation of 7d was much rapid, affording 60% yield
in 3 h, but the diphenyl substituted tertiary alcohol
was totally inert toward intramolecular O-arylation
(entries 7 and 8).
Table 2. Pd-catalyzed asymmetric allylic alkylationa
Ph
Ph
CO2Me
cat. [Pd]/L*
BSA, LiOAc
Ph
Ph
+
OAc
CO2Me
MeO2C
14
CO2Me
12
13
Entry Solvent Temperature Time (h) Yieldb (%) eec (%)
1d
2e
3
4
5
THF
THF
CH2Cl2 rt
PhMe rt
MeCN rt
Et2O
THF
THF
THF
rt
rt
3
1
3
24
24
0.5
8
3
48
99
99
99
75
86
98
99
99
93
56
58
51
43
37
41
66
83
90
Next we performed ortho-lithiation and phosphination
of the cyclic N,O-(1,2-phenylene)prolinols. It was
known that the alkyloxy substituent on the aromatic
ring (ROAr) was a superior directing group than an
alkylamino moiety (R2NAr).15 The oxygen-directed
ortho-lithiation of 10a–c with n-BuLi/TMEDA, fol-
lowed by addition of Ph2PCl, afforded the phosphin-
ation products 11a and 11b in 34% and 44% yields,
respectively, with 40–50% recovery of 10a and 10b
(Scheme 3).16 Unfortunately, the lithiation and phosph-
ination of 10c were unsuccessful. Only the starting mate-
rial was recovered upon quenching the reaction.17
6
rt
0 °C
rt
7
8f
9f
0 °C
a [Pd(g3-C3H5)Cl]2/11a/LiOAc/12/13/BSA = 2:6:4:100:300:300.
b Isolated yields.
c Determined by chiral HPLC, and all the products are (R)-
configuration.
d [Pd(g3-C3H5)Cl]2/11a = 2:4.
e [Pd(g3-C3H5)Cl]2/11a = 2:8.
With 11a and 11b in hand, we set out to investigate their
application as chiral P,O-ligands in Pd-catalyzed allylic
f Compound 11b as ligand.
R
O
R
O
Ph
Ph
n
-BuLi/TMEDA
Ph2PCl
N
N
R
R
Ph
MeO2C
Ph
Me
P
Pd
ether, -78 oC
-78-0 oC
O
N
CO2Me
Ph
Nu-
PPh2
Ph
Me
(R)-14
10a, R = H (49% recovered)
10b, R = Me (43% recovered)
11a (34%)
11b (44%)
H
Scheme 3.
Scheme 4.

B. Jiang, Z.-G. Huang / Tetrahedron Letters 48 (2007) 1703–1706
1705
Okada, Y.; Minami, T.; Umezu, Y.; Nishikawa, S.; Mori,
R.; Nakayama, Y. Tetrahedron: Asymmetry 1991, 2, 667–
682.
backbone, while the quasi-equatorial lone pair might ex-
hibit distinct donating and coordinating characteristics.
Assuming a bidentate chelating mode, the preferential
attack of deprotonated malonate trans to the phospho-
rous atom at a W-type 1,3-diphenyl allyl complex would
lead to an (R)-product.
8. (a) Kuriyama, M.; Nagai, K.; Yamada, K.-I.; Miwa, Y.;
Taga, T.; Tomioka, K. J. Am. Chem. Soc. 2002, 124, 8932–
8939; Arylation: (b) Kuriyama, M.; Soeta, T.; Hao, X.;
Chen, Q.; Tomioka, K. J. Am. Chem. Soc. 2004, 126,
8128–8129.
To conclude, the chiral P,O-ligands have been derived
from N,O-(1,2-phenylene)prolinols, which have been
generated by the N,O-arylation of (S)-prolinols and 1-
bromo-2-iodo-benzene with CuI-catalysis. Their use in
Pd-catalyzed asymmetric allylic alkylation of malonate
with 1,3-dipenyl 2-propenyl acetate has been demon-
strated, and a P,O-bidentate working mode is proposed
to rationale the stereochemical outcome.
9. (a) Kim, Y. K.; Lee, S. J.; Ahn, K. H. J. Org. Chem. 2000,
65, 7807–7813; (b) Lee, Y.-H.; Kim, Y. K.; Son, J.-H.;
Ahn, K. H. Bull. Korean Chem. Soc. 2003, 24, 225–228; (c)
Mino, T.; Kashihara, K.; Yamashita, M. Tetrahedron:
Asymmetry 2001, 12, 287–291; Similar atropisomeric P,O-
ligands: (d) Clayden, J.; Johnson, P.; Pink, J. H.; Helliwell,
M. J. Org. Chem. 2000, 65, 7033–7040; (e) Dai, W.-M.;
Yeung, K. K. Y.; Liu, J.-T.; Zhang, Y.; Williams, I. D.
Org. Lett. 2002, 4, 1615–1618; Application in Heck
reaction: (f) Dai, W.-M.; Yeung, K. K. Y.; Wang, Y.
Tetrahedron Lett. 2004, 60, 4425–4430.
10. (a) Zhang, A.; RajanBabu, T. V. Org. Lett. 2004, 6, 1515–
1517; (b) Zhang, A.; RajanBabu, T. V. Org. Lett. 2004, 6,
3159–3161; (c) Zhang, A.; RajanBabu, T. V. J. Am. Chem.
Soc. 2006, 128, 54–55; MOP-type Ligands: (d) Nomura,
N.; Jin, J.; Park, H.; RajanBabu, T. V. J. Am. Chem. Soc.
1998, 120, 459–460; (e) RajanBabu, T. V.; Nomura, N.;
Jin, J.; Radetich, B.; Park, H.; Nandi, M. Chem. Eur. J.
1999, 5, 1963–1968; (f) Nandi, M.; Jin, J.; RajanBabu, T.
V. J. Am. Chem. Soc. 1999, 121, 9899–9900; (g) Rajan-
Babu, T. V.; Nomura, N.; Jin, J.; Nandi, M.; Park, H.;
Sun, X. J. Org. Chem. 2003, 68, 8431–8446.
Acknowledgement
We thank the National Natural Science Foundation of
China and Shanghai Municipal Committee of Science
and Technology for financial support.
References and notes
1. (a) Pfaltz, A.; Drury, W. J., III. Proc. Natl. Acad. Sci.
U.S.A. 2004, 101, 5723–5726; (b) Guiry, P. J.; Saunders,
C. P. Adv. Synth. Catal. 2004, 346, 497–537; (c) Vyskocil,
S.; Smrcina, M.; Hanus, V.; Polasek, M.; Kocovsky, P. J.
Org. Chem. 1998, 63, 7738–7748.
2. (a) Takahashi, Y.; Yamamoto, Y.; Katagiri, K.; Danjo,
H.; Yamaguchi, K.; Imamoto, T. J. Org. Chem. 2005, 70,
9009–9012; (b) Terfort, A.; Brunner, H. J. Chem. Soc.,
Perkin Trans. 1 1996, 1467–1479; (c) Mateus, N.; Routa-
boul, L.; Daran, J.-C.; Manoury, E. J. Organomet. Chem.
2006, 691, 2297–2310.
3. (a) Lagasse, F.; Kagan, H. B. Chem. Pharm. Bull. 2000, 48,
315–324; (b) Hayashi, T. Acc. Chem. Res. 2000, 33, 354–
362; (c) Bader, A.; Lindner, E. Coord. Chem. Rev. 1991,
108, 27–110.
4. (a) Knowles, W. S. Angew. Chem., Int. Ed. 2002, 41, 1998–
2007; (b) Hayashi, T.; Iwamura, H.; Naito, M.; Matsu-
moto, Y.; Uozumi, Y.; Miki, M.; Yanagi, K. J. Am. Chem.
Soc. 1994, 116, 775–776; (c) Edwards, C. W.; Shipton, M.
R.; Alcock, N. W.; Clase, H.; Wills, M. Tetrahedron 2003,
59, 6473–6480.
5. (a) Kumar, P. G. A.; Dotta, P.; Hermatschweiler, R.;
Pregosin, P. S.; Albinati, A.; Rizzato, S. Organometallics
2005, 24, 1306–1314; (b) Kocovsky, P.; Vyskocil, S.;
Cisarova, I.; Sejbal, J.; Tislerova, I.; Smrcina, M.; Lloyd-
Jones, G. C.; Stephen, S. C.; Butts, C. P.; Murray, M.;
Langer, V. J. Am. Chem. Soc. 1999, 121, 7714–7715.
6. (a) Grushin, V. V. Chem. Rev. 2004, 104, 1629–1662; (b)
Cote, A.; Boezio, A. A.; Charette, A. B. Proc. Natl. Acad.
Sci. U.S.A. 2004, 101, 5405–5410; (c) Boezio, A. A.;
Pytkowicz, J.; Cote, A.; Charette, A. B. J. Am. Chem. Soc.
2003, 125, 14260–14261; (d) Faller, J. W.; Grimmond, B.
J.; D’Alliessi, D. J. J. Am. Chem. Soc. 2001, 123, 2525–
2529; (e) Marshall, W. J.; Grushin, V. V. Organometallics
2003, 22, 555–562.
11. Jiang, B.; Huang, Z.-G.; Cheng, K.-J. Tetrahedron:
Asymmetry 2006, 17, 942–951.
12. Buchwald et al. reported that great selectivity (N/O >50/1)
was achieved by choice of NaOH and i-PrOH or DMSO/
H2O as the base and solvent in CuI-catalyzed C–N or C–O
bond formation between amino alcohols and iodoarenes:
(a) Job, G. E.; Buchwald, S. L. Org. Lett. 2002, 4, 3703–
3706; (b) Lu, Z.; Twieg, R. J.; Huang, S. D. Tetrahedron
Lett. 2003, 44, 6289–6292.
20
13. Compound 9b: ½aꢀD +75 (c 0.70, CHCl3). IR: 3464, 2972,
2871, 1584, 1473, 1301, 1157, 1134, 1112, 1027, 952,
1
755 cmꢁ1. H NMR (300 MHz, CDCl3): d 7.57 (dd, 1H,
J = 1.0, 7.6 Hz), 7.28–7.23 (m, 2H), 6.94–6.89 (m, 1H),
3.78 (dd, 1H, J = 6.6, 8.1 Hz), 3.69–3.61 (m, 1H), 2.83–
2.75 (m, 1H), 2.67 (s, 1H), 2.10–1.78 (m, 4H), 1.14 (s, 3H),
0.90 (s, 3H). 13C NMR (75 MHz): d 151.7, 133.4, 128.2,
124.8, 123.8, 122.6, 72.7, 69.3, 57.7, 29.1, 28.0, 25.9, 25.2.
EIMS: 284 ([M+H]+, 10.2%), 286 (8.6%), 224 (83%), 226
(100%); HRMS: [M+H]+ calcd for C13H19NOBr+
20
284.0645, found 284.0648. Compound 9c: ½aꢀD +56.5 (c
0.99, CHCl3). IR: 3481, 2968, 1584, 1472, 1302, 1130,
1027, 959, 755 cmꢁ1. 1H NMR: d 7.57 (d, 1H, J = 7.8 Hz),
7.26–7.22 (m, 2H), 6.95–6.89 (m, 1H), 3.88 (t, 1H,
J = 7.5 Hz), 3.62–3.54 (m, 1H), 2.81–2.74 (m, 1H), 2.76
(s, 1H), 2.08–2.00 (m, 2H), 1.88–1.74 (m, 2H), 1.63–1.53
(m, 1H), 1.40–1.33 (m, 1H), 1.25–1.01 (m, 2H), 0.85 (t, 3H,
J = 7.5 Hz), 0.62 (t, 3H, J = 7.6 Hz). 13C NMR: d 152.0,
133.3, 128.0, 124.8, 123.7, 122.8, 76.2, 65.9, 58.0, 29.3,
27.3, 25.9, 25.7, 7.9, 7.7. EIMS: 312 ([M+H]+, 1.9%), 314
(1.8%), 224 (85%), 226 (100%); HRMS: [M+H]+ calcd for
C15H23NOBr+ 312.0958, found 312.0970. Compound 9d:
20
Mp: 155–156 °C. ½aꢀD +112.5 (c 1.07, CHCl3). IR: 3385,
3057, 2841, 1659, 1599, 1587, 1493, 1473, 1449, 1373, 1027,
1
704, 695 cmꢁ1. H NMR: d 7.59–7.56 (m, 2H), 7.36–7.29
(m, 4H), 7.24–7.13 (m, 2H), 7.09 (d, 1H, J = 7.5 Hz), 6.98
(t, 1H, J = 7.6 Hz), 6.86 (t, 2H, J = 7.8 Hz), 6.78–6.68 (m,
2H), 4.94 (dd, 1H, J = 4.4, 8.9 Hz), 4.64 (s, 1H), 3.64–3.59
(m, 1H), 2.79 (m, 1H), 2.17–2.12 (m, 1H), 1.97–1.82 (m,
3H). 13C NMR: d 148.86, 145.96, 145.72, 132.40, 130.03,
7. (a) Inoue, H.; Nagaoka, Y.; Tomioka, K. J. Org. Chem.
2002, 67, 5864–5867; (b) You, S.-L.; Luo, Y.-M.; Deng,
W.-P.; Hou, X.-L.; Dai, L.-X. J. Organomet. Chem. 2001,
637, 845–849; (c) Knuhl, G.; Sennhenn, P.; Helmchen, G.
J. Chem. Soc., Chem. Commun. 1995, 1845–1846; (d)

1706
B. Jiang, Z.-G. Huang / Tetrahedron Letters 48 (2007) 1703–1706
128.02, 127.76, 127.11, 126.28, 125.76, 125.57, 125.53,
136.85, 136.71, 134.52, 134.47, 133.89, 133.85, 133.63,
133.59, 128.31, 128.30, 128.19, 128.15, 128.10, 128.06,
123.48, 123.34, 121.83, 121.80, 120.19, 112.83, 68.3, 55.2,
47.8, 28.3, 23.7. 31P NMR (121 MHz): d ꢁ15.8. HRMS:
[M+H]+ calcd for C23H23NOP+ 360.1512, found
125.48, 123.77, 78.6, 68.7, 58.0, 29.5, 25.5. EIMS: 389
([MꢁH2O]+, 0.5%), 391 (0.4%), 224 (75%), 226 (100%).
Anal. Calcd for C23H22NOBr: C, 67.65; H, 5.43; N, 3.43.
Found: C, 67.86; H, 5.35; N, 3.11. Compound 10b:
20
20
½aꢀD +27 (c 0.5, CHCl3). IR: 2976, 2840, 1686, 1607,
360.1522. Compound 11b: ½aꢀD +124 (c 0.95, CHCl3). IR:
1
1508, 1372, 1236, 1141, 740 cmꢁ1. H NMR: d 6.87–6.79
3005, 1714, 1589, 1477, 1437, 1363, 1223, 1093, 913,
(m, 2H), 6.59 (t, 1H, J = 7.5 Hz), 6.49 (d, 1H, J = 7.8 Hz),
3.41–3.34 (m, 2H), 3.23 (dd, 1H, J = 5.5, 9.7 Hz), 2.09–
1.95 (m, 3H), 1.57–1.50 (m, 1H), 1.38 (s, 3H), 1.05 (s, 3H).
13C NMR: d 141.9, 134.4, 121.1, 116.5, 116.0, 110.8, 74.2,
63.4, 46.9, 28.1, 26.0, 23.2, 19.0. HRMS: [M+Na]+ calcd
for C13H17NONa+ 226.1202, found 226.1210. Compound
734 cmꢁ1 1H NMR: d 7.42–7.31 (m, 10H), 6.73 (t, 1H,
.
J = 7.6 Hz), 6.49 (d, 1H, J = 7.2 Hz), 6.06–6.02 (m, 1H),
3.36 (dd, 2H, J = 5.5, 7.3 Hz), 3.20 (dd, 1H, J = 5.5,
9.7 Hz), 2.06–1.92 (m, 3H), 1.48–1.21 (m, 1H), 1.16 (s,
3H), 0.66 (s, 3H). 13C NMR: d 143.5 (d, J = 14.9 Hz),
137.34, 137.21, 137.14, 137.01, 134.40, 134.12, 133.98,
133.73, 128.39, 128.08, 128.06, 128.04, 127.99, 127.94,
123.99, 123.85, 120.86, 120.83, 120.34, 120.30, 111.48,
74.6, 63.3, 47.0, 27.9, 25.6, 23.3, 18.5. 31P NMR: d -14.9.
HRMS: [M+H]+ calcd for C25H27NOP+ 388.1825, found
388.1822.
20
10c: ½aꢀD ꢁ12 (c 0.90, CHCl3). IR: 2974, 1602, 1512, 1463,
1
1269, 946, 750 cmꢁ1. H NMR: d 6.86–6.81 (m, 2H), 6.59
(t, 1H, J = 7.6 Hz), 6.48 (d, 1H, J = 7.5 Hz), 3.44–3.37 (m,
1H), 3.35–3.30 (m, 1H), 2.08–1.85 (m, 4H), 1.67–1.55 (m,
2H), 1.52–1.42 (m, 1H), 1.38–1.26 (m, 1H), 1.00 (t, 3H,
J=7.6 Hz), 0.85 (t, 3H, J = 7.5 Hz). 13C NMR: d 142.1,
121.0, 116.4, 116.1, 110.7, 77.2, 61.0, 46.6, 28.3, 27.5, 23.4,
22.4, 7.8, 6.7. HRMS: 231.1623 calcd for C15H22NO+,
found 231.1624.
17. No racemization occurred in this process as evidenced by
the optical purity measurement of the recovered 10a–c.
18. (a) Trost, B. M. Acc. Chem. Res. 1980, 13, 385–393; (b)
Tsuji, J. Tetrahedron 1986, 42, 4361–4401; (c) Consiglio,
G.; Waymouth, R. M. Chem. Rev. 1989, 89, 257–276; (d)
Frost, C. G.; Howarth, J.; Williams, J. M. J. Tetrahedron:
Asymmetry 1992, 3, 1089–1122; (e) Reiser, O. Angew.
Chem., Int. Ed. 1993, 32, 547–549; (f) Trost, B. M. Acc.
Chem. Res. 1996, 29, 355–364; (g) Trost, B. M.; van
Vruken, D. L. Chem. Rev. 1996, 96, 395–422; (h) Williams,
J. M. J. Synlett 1996, 705–710; (i) Johannsen, M.;
Jørgensen, K. A. Chem. Rev. 1998, 98, 1689–1708; (j)
Helmchen, G. J. Organomet. Chem. 1999, 576, 203–214;
(k) Pfaltz, A. Chimia 2001, 55, 708–714; (l) Hayashi, T. J.
Organomet. Chem. 1999, 576, 195–202; (m) Dai, L.-X.; Tu,
T.; You, S.-L.; Deng, W.-P.; Hou, X.-L. Acc. Chem. Res.
2003, 36, 659–667; (n) Trost, B. M.; Crawley, M. L. Chem.
Rev. 2003, 103, 2921–2944; (o) Trost, B. M. J. Org. Chem.
2004, 69, 5813–5837.
14. Optical comparisons of 9a, 10a, and debrominated 9a with
those obtained in Ref. 11 indicate there is no racemization
for this technique.
15. (a) Snieckus, V. Chem. Rev. 1990, 90, 879–933; (b)
Schlosser, M. Eur. J. Org. Chem. 2001, 3975–3984; (c)
Mongin, F.; Queguiner, G. Tetrahedron 2001, 57, 4059–
4090; (d) Whisler, M. C.; MacNeil, S.; Snieckus, V.; Beak,
P. Angew. Chem., Int. Ed. 2004, 43, 2206–2225; (e)
Gschwend, H. W.; Rodriguez, H. R. Org. React. 1979,
26, 1–360; (f) Clayden, J. In The Chemistry of Organo-
lithium Compounds; Rappoport, Z., Marek, I., Eds.;
Wiley: Chichester, 2004; pp 495–646.
20
16. Compound 11a: Mp: 50–60 °C. ½aꢀD +27.3 (c 0.50, CHCl3).
IR: 2975, 2869, 1735, 1584, 1472, 1434, 1365, 1321, 1203,
999, 696 cmꢁ1 1H NMR: d 7.34–7.31 (m, 10H), 6.78 (t,
.
1H, J = 7.9 Hz), 6.59 (d, 1H, J = 7.8 Hz), 5.99 (t, 1H,
J = 6.3 Hz), 4.35 (dd, 1H, J = 3.0, 9.9 Hz), 3.55–3.45 (m,
2H), 3.32–3.17 (m, 2H), 2.08–1.95 (m, 3H), 1.44–1.34 (m,
1H). 13C NMR: d 144.41 (d, J = 16.6 Hz), 137.11, 136.98,
19. Following the procedure described in Ref. 11.
20. Trabesinger, G.; Albinati, A.; Feiken, N.; Kunz, R. W.;
Pregosin, P. S.; Tschoerner, M. J. Am. Chem. Soc. 1997,
119, 6315–6323.