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M. Amador et al. / Tetrahedron Letters 51 (2010) 935–938
16. Relative configurations of cyclic carbamates 4 were readily determined by 1H
chromatography (hexane/AcOEt 7:3) to afford 6c (1.790 g, 78%). Colorless oil; Rf
(CH2Cl2): 0.48; ½a D20
ꢄ
+32.0 (c 1.0 in CHCl3); 1H NMR (400 MHz, CDCl3): d 0.84 (t,
NMR NOE experiments.
J = 6.8 Hz, 3H, CH3), 0.90 (t, J = 7.0 Hz, 3H, CH3), 1.22–1.37(m, 10H, CH2), 1.38–
1.45 (m, 2H, CH2), 1.51–1.59 (m, 2H, CH2), 1.62–1.69 (m, 2H, CH2), 2.36 (br s,
2H, OH), 4.70 (dt, J = 8.8, 6.8 Hz, 1H, @CH–CH–OH), 4.74 (dd, J = 8.0, 5.2 Hz, 1H,
@CPh–CH–OH), 5.58 (d, J = 8.8 Hz, 1H, CH@), 7.28–7.35 (m, 5H, Ar); 13C NMR
(CDCl3, 101 MHz): d 13.9 and 14.0 (CH3), 22.5, 22.6, 25.3, 25.8, 31.6, 31.8, 36.6,
and 37.8 (CH2), 67.6 (@CHCH–OH), 72.8 (CPhCH–OH), 127.3, 127.8, 127.8,
128.1 and 128.1 (Ar), 134.2 (CH@), 141.4 (Ar), 146.0 (CPh@); IR (film): mmax
3388, 2956, 2931, 2860, 1493, 1459, 1028.
17. For very recent reviews on microwave synthesis, see: (a) Caddick, S.;
Fitzmaurice, R. Tetrahedron 2009, 65, 3325–3355; (b) Polshettiwar, V.;
Varma, R. S. Acc. Chem. Res. 2008, 41, 629–639; (c) Kappe, C. O. Chem. Soc.
Rev. 2008, 37, 1127–1139; (d) Dallinger, D.; Kappe, C. O. Chem. Rev. 2007, 107,
2563–2591.
18. Typical procedure: To a solution of [NiCl2(PPh3)2] (19 mg, 28.6
lmol) in dry THF
(0.6 mL) was added i-PrMgCl (29 L, 57.2 mol, 2.0 M solution in Et2O) at 0 °C
l
l
under Ar. After 10 min the color of the solution changed from green to brown.
Then the mixture was transferred via cannula to a flask containing a solution of
dicarbamate (S,S)-3c (100 mg, 0.143 mmol) in THF (0.6 mL) under Ar and the
mixture was heated in a microwave oven for 2 h to 120 °C (inside pressure was
5–6 bars). Then, the solvent was removed and the crude was filtered through a
short pad of Celite (AcOEt). The solvent was removed and the residue was
purified by flash chromatography (hexane/AcOEt 8:2) to afford a 92:8 mixture
of 4c/40c (40 mg, 0.083 mmol, 58%). (b) Compound 4c: white solid, mp 84–
7. A series of experiments performed with 3a showed even worse regio- and
stereoselectivities.
8. For a recent review on molybdenum-catalyzed asymmetric allylic alkylations,
see: Belda, O.; Moberg, C. Acc. Chem. Res. 2004, 37, 159–167.
9. For a very recent review on iridium-catalyzed asymmetric allylic substitutions,
see: (a) Helmchen, G. In Iridium Complexes in Organic Synthesis; Oro, L. A.,
Claver, C., Eds.; Wiley-Interscience: Weinheim, 2009; pp 211–250; (b)
Takeuchi, R.; Kashio, M. J. Am. Chem. Soc. 1998, 120, 8647–8655; (c) Takeuchi,
R.; Ue, N.; Tanabe, K.; Yamashita, K.; Shiga, N. J. Am. Chem. Soc. 2001, 123, 9525–
9534; For examples of Ir-catalysed intramolecular N-alkylations, see: (d)
Miyabe, H.; Yoshida, K.; Kobayashi, Y.; Matsumura, A.; Takemoto, Y. Synlett
2003, 1031–1033; (e) Welter, C.; Dahnz, A.; Brunner, B.; Streiff, S.; Dübon, P.;
Helmchen, G. Org. Lett. 2005, 7, 1239–1242.
10. (a) Yamamoto, T.; Ishizu, J.; Yamamoto, A. J. Am. Chem. Soc. 1981, 103, 6863–
6869; (b) Cuvigny, T.; Julia, M. J. Organomet. Chem. 1986, 317, 383–408. and
references therein; (c) Cuvigny, T.; Julia, M. J. Organomet. Chem. 1983, 250, C21–
C24.
11. In contrast to the situation with Pd, allylic alkylation takes place mostly at the
more substituted carbon atom when unsymmetrical substrates are used. See,
for instance: Co, T. T.; Paek, S. W.; Shim, S. C.; Cho, C. S.; Kim, T.-J.; Choi, D. W.;
Kang, S. O.; Jeong, J. H. Organometallics 2003, 22, 1475–1482; For a review on
structure–reactivity relationship in allyl complexes of group 10 metals, see:
Kurosawa, H.; Ogoshi, S. Bull. Chem. Soc. Jpn. 1988, 71, 973–984.
12. The use of [Mo(CO)4(bpy)] showed similar trends. This dipyridyl-ligated
molybdenum complex was prepared by the simple ligand exchange between
2,20-bipyridyl (bpy) and Mo(CO)6: Stiddardt, M. H. B. J. Chem. Soc. 1962, 4712–
4715.
85 °C; Rf (hexane/AcOEt 7:3): 0.47; ½a D20
ꢄ
ꢃ47.0 (c 0.6 in CHCl3); 1H NMR
(400 MHz, CDCl3): d 0.80 (t, J = 6.8 Hz, 3H, CH3), 0.92 (t, J = 7.2 Hz, 3H, CH3),
1.15–1.20 (m, 6H, CH2), 1.33–1.40 (m, 6H, CH2), 1.49–1.54 (m, 2H, CH2), 2.25–
2.31 (m, 2H, CH2), 2.42 (s, 3H, CH3–Ar), 4.44 (dd, J = 10.0, 2.8 Hz, 1H, CH–O),
5.92 (dt, J = 15.6, 1.4 Hz, 1H, CH@CHCH2), 6.18 (dt, J = 15.6, 6.8 Hz, 1H, CH@CH–
CH2), 7.23 (d, J = 8.4 Hz, 2H, Ar), 7.39–7.49 (m, 5H, Ar), 7.63 (d, J = 8.4 Hz, 2H,
Ar). 13C NMR (CDCl3, 101 MHz): d 13.8 (CH3), 14.0 (CH3), 21.6 (CH3-Ar), 22.2,
22.4, 25.5, 28.5, 28.9, 31.3, 31.4 and 32.7 (CH2), 74.1 (CPh–NTs), 87.9 (CH–O),
123.5 (TsNCPh–CH@), 127.6, 128.5, 129.0, 129.1, 129.2 and 135.8 (Ar), 137.1
(CH2CH@), 138.9 (C(Ar)), 145.0 (C(Ar)–SO2)), 152.5 (C@O).; IR (KBr): mmax
2929–2860, 1781, 1175, 1090.
19. Experiments performed with 3c and DBU in the presence of 20 mol % of
Sc(OTf)2 (THF, rt or 60 °C) caused the degradation of starting material. The use
of PtCl2 led to the recovery of starting dicarbamate. In THF no reaction was
observed.
20. Lei, A.; Liu, G.; Lu, X. J. Org. Chem. 2002, 67, 974–980.
21. (a) Albert, J.; Granell, J.; Luque, A.; Minguez, J.; Moragas, R.; Font-Bardia, M.;
Solans, X. J. Organomet. Chem. 1996, 522, 87–95; (b) Albert, J.; Granell, J.;
Zafrilla, J.; Font-Bardia, M.; Solans, X. J. Organomet. Chem. 2005, 690, 422–429;
(c) Albert, J.; D’Andrea, L.; Granell, J.; Tavera, R.; Font-Bardia, M.; Solans, X. J.
Organomet. Chem. 2007, 692, 3070–3080.
13. In THF no reaction was observed.
14. (a) Moberg, C. Tetrahedron Lett. 1980, 21, 4539–4542; (b) Bricout, H.;
Carpentier, J.-F.; Mortreux, A. J. Chem. Soc., Chem. Commun. 1995, 1863–1864;
(c) Bricout, H.; Carpentier, J.-F.; Mortreux, A. Tetrahedron 1998, 54, 1073–1084;
(d) Berkowitz, D. B.; Bose, M.; Choi, S. Angew. Chem., Int. Ed. 2002, 41, 1603–
1607; (e) Berkowitz, D. B.; Maiti, G. Org. Lett. 2004, 6, 2661–2664.
15. A series of experiments were performed in which we changed the amount of
catalyst (0.1–0.4 mol % of [Ni(COD)2]), in the presence or absence of base
(LiHMDS), ligands (PPh3, BINAP), and temperatures (rt to MW heating to
120 °C) gave poor and/or erratic results.
22. For a very recent review on palladacycles, see Dupont, J.; Consorti, C. S.;
Spencer, J. Chem. Rev. 2005, 105, 2527–2572.
23. Dalcanale, E.; Montanari, F. J. Org. Chem. 1986, 51, 567–569.
24. Carlsen, H. J.; Katsuki, T.; Martin, V. S.; Sharpless, K. B. J. Org. Chem. 1981, 46,
3936–3938.
25. For very recent reviews on stereoselective construction of
-amino acids, see: (a) Ohfune, Y.; Shinada, T. Eur. J. Org. Chem. 2005, 5127–
5143; (b) Byun, H.-S.; Lu, X.; Bittman, R. Synthesis 2006, 2447–2474.
a,a-disubstituted
a