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M. Pucheault et al. / Tetrahedron Letters 45 (2004) 4729–4732
11. Unpublished results.
References and notes
12. For a racemic version: (a) Navarre, L.; Darses, S.; Genet,
J.-P. Eur. J. Org. Chem. 2004, 1, 69; For tandem 1,4-
addition-enantioselective protonation: (b) Navarre, L.;
Darses, S.; Genet, J.-P. Angew. Chem., Int. Ed. 2004, 43,
719.
1. For reviews on enantioselective conjugate additions see:
(a) Perlmutter, P. Conjugate Addition in Organic Synthesis;
Pergamon: Oxford, 1992; (b) Schmalz, H.-G. In Compre-
hensive Organic Synthesis; Trost, B. M., Flemming, I.,
Eds.; Pergamon: Oxford, 1991; Vol. 4, Chapter 1–5;
13. Navarre, L.; Darses, S.; Genet, J.-P. Chem. Commun. 2004
€
(c) Krause, N.; Hoffmann-Roder, A. Synthesis 2001, 171;
14. General procedure for the 1,4-addition of potassium
trifluoro(organo)borates on a,b-unsaturated amides (entry
4): A mixture of potassium trifluoro(3-methoxyphen-
yl)borate (198 mg, 1 mmol), N-benzylbut-2-enamide
(87.5 mg, 0.5 mmol), Rh(cod)2PF6 (7.0 mg, 3mol %) and
(R)-Binap (10.3mg, 3.3mol %) were charged in a flask
then a degassed toluene/water mixture (2:0.5 mL) was
added at room temperature. The flask was placed in a
preheated oil bath at 105–110 °C until completion of the
reaction (followed by GC analysis). Direct purification by
silica gel chromatography afforded 3ca as a white solid
(104 mg, 93% yield). Mp ¼ 76 °C. Rf (cyclohexane/ethyl
(d) Sibi, M. P.; Manyem, S.. Tetrahedron 2000, 56, 8033.
2. Alexakis, A.; Benhaim, C. Eur. J. Org. Chem. 2002,
3221.
3. Takaya, Y.; Ogasawara, M.; Hayashi, T.; Sakai, M.;
Miyaura, N. J. Am. Chem. Soc. 1998, 120, 5579.
4. Reviews: (a) Hayashi, T. Synlett 2001, 879; (b) Hayashi,
T.; Yamasaki, K. Chem. Rev. 2003, 103, 2829.
5. For a study on the mechanism see: Hayashi, T.; Taka-
hashi, M.; Takaya, Y.; Ogasawara, M. J. Am. Chem. Soc.
2002, 124, 5052.
6. (a) Cuvigny, T.; Normant, H. Bull. Soc. Chim. Fr. 1961,
2423; (b) Barbot, F.; Kadib-Elban, A.; Miginiac, P.
Tetrahedron Lett. 1983, 24, 5089; (c) Nagashima, H.;
Ozaki, N.; Washiyama, M.; Itoh, K. Tetrahedron Lett.
1985, 26, 657; (d) Liao, S.; Han, Y.; Qiu, W.; Bruck, M.;
Hruby, V. J. Tetrahedron Lett. 1996, 37, 7917, and
references cited therein.
7. Sakuma, S.; Miyaura, N. J. Org. Chem. 2001, 66, 8944.
8. Senda, T.; Ogasawara, M.; Hayashi, T. J. Org. Chem.
2001, 66, 6852.
1
acetate: 3/2) ¼ 0.30. H NMR (200 MHz, CDCl3, d) 1.33
(3H, d, J ¼ 7:0 Hz, CH3), 2.47 (2H, d, J ¼ 7:6 Hz,
CH2CO), 3.32 (1H, app hex, J ¼ 7:0 Hz, CHAr), 3.79
(3H, s, OCH3), 4.29 (1H, dd, J ¼ 5:8 Hz, J ¼ 14:8 Hz,
NCH2), 4.41 (1H, dd, J ¼ 5:8 Hz, J ¼ 14:8 Hz, NCH2),
5.56 (1H, br s, NH), 6.75–6.86 (3H, m, HAr), 7.06 (2H, dd,
J ¼ 7:0 Hz, J ¼ 2:6 Hz, HAr), 7.19–7.31 (4H, m, HAr). 13C
NMR (50 MHz, CDCl3, d): 21.8, 37.1, 43.4, 45.7, 55.1,
111.6, 112.8, 119.1, 127.3, 127.5, 128.6, 129.6, 138.1, 147.5,
9. For review on potassium organotrifluoroborates chemis-
try see: Darses, S.; Genet, J.-P. Eur. J. Org. Chem. 2003,
4313.
10. (a) Pucheault, M.; Darses, S.; Genet, J.-P. Tetrahedron
Lett. 2002, 43, 6155; (b) Pucheault, M.; Darses, S.; Genet,
J.-P. Eur. J. Org. Chem. 2002, 3552.
159.8, 171.4. MS (IE, m=z): 283(43%, M þÁ), 148 (100%), 91
28
(48%). ½aꢀ þ35.3 (c 0.8, CHCl3). HPLC (Chiralcel OD-H,
D
n-hexane/propan-2-ol: 95/5, 1 mL minꢁ1): t1 ¼ 54:5 min,
t2 ¼ 59:9 min. C18H21NO2 calcd: C: 76.29; H: 7.47; N:
4.94; found: C: 76.17; H: 7.51; N: 4.87.