Erratum: "enantioselective protonation of prochiral enolates in the asymmetric synthesis of (S)-naproxen": [Tetrahedron Lett. 44 (2003) 2023] (Tetrahedron Letters (2003) 44 (2023) DOI: 10.1016/S0040-4039(03)00217-X)

Full text of DOI:10.1016/j.tetlet.2004.12.106

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 1221–1222
Corrigendum
Corrigendum to ‘‘Enantioselective protonation of prochiral
enolates in the asymmetric synthesis of (S)-naproxen’’
[Tetrahedron Lett. 44 (2003) 2023]
*
´
Roberto Melgar-Fernandez and Eusebio Juaristi
´ ´ ´
Departamento de Quımica, Centra de Investigacion y de Estudios Avanzados del Instituto Politecnico National,
´
Apartado postal 14-740, 07000 Mexico, D.F., Mexico
A central section in the above manuscript describes the
yl)-N,N-bis(1S-a-phenylethyl)acetamide (S,S)-11, by
refluxing 3H-benzofuran-2-one and (S,S)-bis-a-
phenylethylamine in toluene. By contrast, a-phenylethyl-
amine does react with 3H-benzofuran-2-one to give
(S)-10 in 95% yield under mild conditions
(Scheme 2).1,2
treatment of racemic naproxen ester derivatives ( )-2,
( )-3 and ( )-4 with achiral base LDA to give the corre-
sponding prochiral enolates 2-Li, 3-Li and 4-Li, which
were then reprotonated with the novel chiral Brønsted
acids (S)-10 and (S,S)-11 (Scheme 1).
Recently, we were unable to reproduce the described
procedure1,2 for the preparation of 2-(2-hydroxyphen-
We have now developed a successful route for the
synthesis of chiral phenol (S,S)-11,3 whose correct
CH3
CH3
OR
LDA
Toluene
CO2R
O
Li
CH3O
CH3O
2-4-Li
A*-H
( )-2, R = CH3
( )-3, R = i-Pr
( )-4, R = t-Bu
enantioenriched 2-4 ?
A*-H =
CH3
O
Ph
Ph
H
N
CH3
CH3
N
O
Ph
OH
(S)-10
OH
(S,S)-11
Scheme 1.
DOI of original article: 10.1016/S0040-4039(03)00217-X
*
Corresponding author. Tel.: +52 55 5061 3722; fax: +52 55 5747 7132; e-mail: juaristi@relaq.mx
0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.12.106

1222
Corrigendum / Tetrahedron Letters 46 (2005) 1221–1222
H
N
CH3
CH3
5 min, rt
(a)
(b)
+
H2N
O
O
O
Ph
toluene
OH
Ph
95 % yield
(S)-10
CH3
Ph
Ph
CH3
Ph
CH3
N
∆
+
HN
O
O
O
toluene
OH
(S,S)-11
2
Scheme 2.
(s, 1H). 13C NMR (CDCl3, 100.5 MHz): d 21.7, 41.1, 49.7,
118.0, 120.5, 121.7, 126.2, 127.7, 128.9, 129.3, 130.7, 142.4,
156.1, 172.7. IR (KBr) m (cmꢁ1): 3317, 1620, 1546, 1456,
1265, 1234. MS m/z (%): 255 (M+, 59), 151 (42), 134 (40),
105 (100), 79 (8). Anal. Calcd for C16H17NO2 (255.32): C,
75.27; H, 6.71; N, 5.49. Found: C, 75.05; H, 6.74; N, 5.85.
2-(2-Hydroxyphenyl)-N,N-bis(1S-a-phenylethyl)acetamide,
analytical data are presented in Ref. 4 below. These data
must replace those reported in Ref. 12 of the title article.
Regarding the protonation reaction of enolates 2–4-Li
with chiral Brønsted acids (S)-10 and (S,S)-11 (Scheme
1),5 contrary to the information provided in Table 3 of
the article being reexamined, we found no enantiomeric
excess in the recovered esters 2–4.5–7
20
(S,S)-11. Mp 119–120 °C. ½aꢀD ꢁ184.1 (c 1.0, CHCl3).
1H NMR (CDCl3, 400 MHz): d 1.73 (d, J = 7.3 Hz, 3H),
1.92 (d, J = 7.0 Hz, 3H), 3.39 (d, J = 14.5 Hz, 1H), 3.55 (d,
J = 14.5 Hz, 1H), 4.97 (q, J = 6.9 Hz, 1H), 5.94 (br s, 1H),
6.10 (br s, 1H), 6.60 (t, J = 7.3 Hz, 1H), 6.85–6.97 (m, 13H),
7.12 (dt, J1 = 8.1 Hz, J2 = 1.4 Hz, 1H), 7.18–7.40 (m, 9H),
10.8 (s, 1H). 13C NMR (CDCl3, 100.5 MHz): d 17.9, 20.9,
39.9, 52.5, 53.5, 118.5, 119.8, 121.9, 126.6, 127.9, 128.5,
128.8, 129.0, 129.2, 129.3, 131.0, 140.1, 141.5, 157.6, 175.3.
IR (KBr) m (cmꢁ1): 3086, 1616, 1589, 1455, 1336, 1168. MS
m/z (%): 359 (M+, 5), 255 (100), 210 (19), 105 (97), 91 (13).
Anal. Calcd for C24H25NO2 (359.47): C, 80.19; H, 7.01; N,
3.90. Found: C, 79.84; H, 7.35; N, 3.98.
Acknowledgements
We are grateful to Dr. Charles Vandenbossche, Sepra-
cor Inc., for the exchange of relevant information.
References and notes
1. Mun˜oz-Mun˜iz, O.; Juaristi, E. J. Org. Chem. 2003, 68,
3781.
2. Mun˜oz-Mun˜iz, O.; Juaristi, E. Tetrahedron 2003, 59, 4223.
´
3. Melgar-Fernandez, R.; Juaristi, E., submitted for
publication.
5. The general protocol developed by Fehr et al. was followed:
Fehr, C.; Galindo, J.; Farris, I.; Cuenca, A. Helv. Chim.
Acta 2004, 87, 1737.
6. HPLC analysis using a Chiralcel OD column, 254 nm UV
detector, 1.0 mL/min. Hexane–i-PrOH, 99:1.
7. In the title article, enantiopure (S)-4 (R = t-Bu in Table 1) is
4. 2-(2-Hydroxyphenyl)-N-(1S-a-phenylethyl)acetamide, (S)-
20
1
10. Mp 118–119 °C. ½aꢀD ꢁ72.2 (c 1.0, CHCl3). H NMR
(CDCl3, 400 MHz): d 1.45 (d, J = 6.9 Hz, 3H), 3.55 (dd,
J1 = 14.3 Hz, J2 = 4.1 Hz, 2H), 5.06 (dq, J1 ffi J2 = 7.3 Hz,
1H), 6.56 (d, J = 6.9 Hz, 1H), 6.80–7.32 (m, 9H), 9.87
28
reported as a wax with ½aꢀD +27.1 (c 1.0, CHC13). The
20
correct physical properties of (S)-4 (this work) are: mp
90–92 °C, ½aꢀD +22.6 (c 1.0, CHCl3).