36
D. Enders et al.
LETTER
(9) By aldol-type reaction of an anion to nitrogen with a
carbonyl compound or pinacol-type reaction of imino- or
oximino compounds with a carbonyl compound.
washed with sat. NaCl solution, dried over anhyd Na2SO4
and concentrated in vacuo. After the isomer ratio was
determined, flash column chromatography of the residue on
silica gel eluting with pentane–Et2O gave 7a.
(10) Sequential addition of the heteroatoms to olefins leads to
trans product. Simultanous introduction gives cis product.
(11) Most common method is the addition of an amino equivalent
(azide or carbamate) to oxygen containing substrates.
(12) For recent examples, see: (a) Jordá-Gregori, J. M.;
González-Rosende, M. E.; Cava-Montesinos, P.; Sepúlveda-
Arques, J.; Galeazzi, R.; Orena, M. Tetrahedron: Asymmetry
2000, 11, 3769. For a recent example of one-pot-preparation
of trans oxazolidin-2-ones, see: (b)Barta, N. S.; Sidler, D.
R.; Somerville, K. B.; Weissman, S. A.; Larsen, R. D.;
Reider, P. J. Org. Lett. 2000, 2, 2821. (b) Hakogi, T.;
Monden, Y.; Iwama, S.; Katsumura, S. Org. Lett. 2000, 2,
2627. (c) Tomasini, C.; Vecchione, A. Org. Lett. 1999, 1,
2153. (d) Bergmeier, S. C.; Stanchina, D. M. J. Org. Chem.
1999, 64, 2852. (e) Sakamoto, Y.; Shiraishi, A.; Seonhec, J.;
Nakata, T. Tetrahedron Lett. 1999, 40, 4203. (f) Zhao, H.;
Thurkauf, A. Synlett 1999, 1280. (g) Agami, C.; Amiot, F.;
Couty, F.; Dechoux, L.; Kaminsky, C.; Venier, O.
(19) Larson, G. L.; Klesse, R. J. Org. Chem. 1985, 50, 3627.
(20) Connor, D. S.; Klein, G. W.; Taylor, G. N. Org. Synth. 1972,
16.
(21) Same configuration of the generated stereogenic center as in
7a–d, but change of priority ranking leads to (R)-
nomenclature.
(22) Typical Procedure of 1,2-Addition to Glycol Aldehyde
SAMP-hydrazone, Cyclization and N,N-Cleavage to
Oxazolidin-2-ones: A solution of t-butyllithium (1.6 M) in
hexane (9.6 mmol) was slowly added to a solution of 7a (4.8
mmol) in anhyd THF (24 mL) at –100 °C. In case of freshly
prepared RLi reagent (entry 6, 7) the hydrazone solution was
added. The solution was stirred for 15 h and allowed to warm
up to –30 °C. After cooling down to –78 °C MOCCl (48
mmol) was rapidly added. After being stirred at that
temperature for 15 h, the reaction mixture was quenched
with sat. NaHCO3 solution (15 mL). The aq portion was
extracted with Et2O (3 15 mL), the combined organic
layers were washed with brine, dried over anhyd Na2SO4 and
concentrated in vacuo. After filtration through silicia gel
washing with pentane–Et2O the crude product was dissolved
in dry THF (15 mL) and TBAF (1 M) in THF (14.4 mmol)
was added at r.t. After being stirred for 4 d at that
Tetrahedron: Asymmetry 1998, 9, 3955.
(13) (a) Enders, D.; Reinhold, U. Angew. Chem., Int. Ed. Engl.
1995, 34, 1219; Angew. Chem. 1995, 107, 1332. (b)Enders,
D.; Reinhold, U. Liebigs Ann. Chem. 1996, 11.
(14) Ridder, A.; Enders, D. RWTH Aachen, unpublished results,
2000. For the ozonolysis of the silyl-protected 1,4-
dihydroxy-cis-2-butene see also: Nicolaou, K. C.; Liu, J.-J.;
Yang, Z.; Ueno, H.; Sorensen, E. J.; Claiborne, C. F.; Guy,
R. K.; Hwang, C.-H.; Nakada, M.; Nantermet, P. G. J. Am.
Chem. Soc.; 1995, 117, 634; the resulting aldehyde was
allowed to react with the hydrazine without further
purification.
(15) (a) Enders, D.; Klatt, M. In Encyclopedia of Reagents for
Organic Synthesis, Vol. 1; Paquette, L. A., Ed.; John Wiley
and Sons: Chichester, 1995, 178. (b) Enders, D. In
Asymmetric Synthesis, Vol. 3; Morrison, J. D., Ed.;
Academic Press: New York, 1984, 275. (c) Enders, D.; Fey,
P.; Kipphardt, H. Org. Synth. 1987, 65, 173 and 183.
(16) For a short review on the synthesis of alkaloids, see: Enders,
D.; Thiebes, C. Pure Appl. Chem. 2001, 73, 573.
(17) For reviews on the 1,2-addition of organometallic reagents,
see: (a) Denmark, S. E.; Nicaise, O. J.-C. Chem. Commun.
1996, 999. (b) Enders, D.; Reinhold, U. Tetrahedron:
Asymmetry 1997, 8, 1895. (c) Bloch, R. Chem. Rev. 1998,
98, 1407. (d) Kobayashi, S.; Ishitani, H. Chem. Rev. 1999,
99, 1069. (e) Merino, P.; Franco, S.; Merchan, F. L.; Tejero,
T. Synlett 2000, 442.
(18) General Procedure of -Alkylation of Glycol Aldehyde
SAMP-hydrazone 6: A solution of 6 (10 mmol) in anhyd
THF (5 mL) was slowly added to a solution of 2.0 equiv
LDA (freshly prepared from n-butyllithium and
temperature, the reaction mixture was concentrated in vacuo
at 35 °C. The residue was filtered through silica gel washing
with pentane–Et2O. The crude product was dissolved in THF
(15 mL) and added to a solution of Li (48 mmol) in NH3 (125
mL) at –78 °C. The solution was allowed to warm up to –
33 °C. After being stirred at the temperature for 40 min, the
reaction mixture was quenched with NH4Cl (2.5 g). NH3 was
removed at r.t. and the residue was extracted with CH2Cl2
(3 10 mL). The combined organic layers were washed with
brine and dried over anhyd Na2SO4 and concentrated in
vacuo. After the isomer ratio was determined, flash column
chromatography of the residue on silica gel eluting with
pentane–Et2O gave the desired product 10b.
(23) For some examples higher temperature of up to 35 °C was
necessary to reduce the reaction time.
(24) (a) Negishi, E.; Swanson, D. R.; Rousset, C. J. J. Org. Chem.
1990, 55, 5406. (b) Bailey, W. F.; Punzalan, E. R. J. Org.
Chem. 1990, 55, 5404.
(25) (a) Cainelli, G.; Panunzio, M.; Contento, M.; Giacomini, D.;
Mezzina, E.; Giovagnoli, D. Tetrahedron 1993, 49, 3809.
(b) Zietlow, A.; Steckhan, E. J. Org. Chem. 1994, 59, 5658.
(26) Up to > 98% de according to ref.13.
(27) Major diastereomer isolated by flash chromatography.
Relative configuration of the two generated centers at the
oxazolidinone ring towards the configurationally known
auxiliary (S’)-center gives the absolute configuration of 9a.
(28) (a) Nübling, C. Dissertation; RWTH Aachen: Germany,
1987. (b) Denmark, S. E.; Nicaise, O.; Edwards, J. P. J. Org.
Chem. 1990, 55, 6219. (c) Enders, D.; Teschner, P.;
Gröbner, R.; Raabe, G. Synthesis 1999, 247. (d) Enders, D.;
Teschner, P.; Raabe, G. Heterocycles 2000, 52, 733.
diisopropylamine) in anhyd THF (20 mL) at –78 °C. After
being stirred at that temperature for 15 h, methyl iodide (30
mmol) was added at –100 °C. The solution was stirred for 1
h at that temperature and then allowed to warm up to r.t.
within 20 h. The reaction mixture was quenched with sat.
NH4Cl solution (15 mL). The aq portion was extracted with
Et2O (3 10 mL), and the combined organic layers were
Synlett 2002, No. 1, 33–36 ISSN 0936-5214 © Thieme Stuttgart · New York