Abstract
The choice of the 2,6-diphenylpiperidine moiety as the N ,N -dialkylamino auxiliary in simple aliphatic dialkylhydrazones and the use of scandium triflate as the catalyst in aqueous media appear as the key strategies that enable the highly diastereoselective nucleophilic addition of ketene silyl acetals and thioacetals. The reaction proceeds to afford the expected adducts in high yields (88-98%) and diastereomeric ratios of up to 99:1. N-N bond cleavage of adducts affords enantiomerically pure β-amino esters.
Key words
asymmetric synthesis - hydrazones - ketene silyl acetals - ketene silyl thioacetals - diastereoselectivity
References
1 Enantioselective Synthesis of β-Amino Acids
Juaristi E.
Soloshonok VA.
Wiley-VCH;
New York:
2005. 2nd edition
2 Kobayashi S.
Ishitani H.
Chem. Rev.
1999,
99:
1069
3a Ishitani H.
Ueno M.
Kobayashi S.
J. Am. Chem. Soc.
1997,
119:
7153
3b Kobayashi S.
Ishitani H.
Ueno M.
J. Am. Chem. Soc.
1998,
120:
431
3c Müller R.
Goesmann H.
Waldmann H.
Angew. Chem. Int. Ed.
1999,
38:
184
3d Akiyama T.
Itoh J.
Yokota K.
Fuchibe K.
Angew. Chem. Int. Ed.
2004,
43:
1566
4a Kobayashi S.
Hamada T.
Manabe K.
J. Am. Chem. Soc.
2002,
124:
5640
4b Kobayashi S.
Matsubara R.
Nakamura Y.
Kitagawa H.
Sugiura M.
J. Am. Chem. Soc.
2003,
125:
2507
4c Hamada T.
Manabe K.
Kobayashi S.
J. Am. Chem. Soc.
2004,
126:
7768
5 Ishitani H.
Ueno M.
Kobayashi S.
J. Am. Chem. Soc.
2000,
122:
8180
6 Kobayashi S.
Hasegawa Y.
Ishitani H.
Chem. Lett.
1998,
1131
7 Josephsohn NS.
Snapper ML.
Hoveyda AH.
J. Am. Chem. Soc.
2004,
126:
3734
8a Fernández R.
Lassaletta JM.
Synlett
2000,
1228
8b Lassaletta JM.
Vázquez J.
Prieto A.
Fernández R.
Raabe G.
Enders D.
J. Org. Chem.
2003,
68:
2698
9 Lassaletta JM.
Alcarazo M.
Fernández R.
Chem. Commun.
2004,
298
10a Fernández R.
Ferrete A.
Lassaletta JM.
Llera JM.
Monge A.
Angew. Chem. Int. Ed.
2000,
39:
2893
10b Fernández R.
Ferrete A.
Lassaletta JM.
Llera JM.
Martín-Zamora E.
Angew. Chem. Int. Ed.
2002,
114:
859
10c Díez E.
Fernández R.
Marqués-López E.
Martín-Zamora E.
Lassaletta JM.
Org. Lett.
2004,
6:
2749
10d Martín-Zamora E.
Ferrete A.
Llera JM.
Muñoz JM.
Pappalardo RR.
Fernández R.
Lassaletta JM.
Chem. Eur. J.
2004,
10:
6111
11 Enders D.
Reinhold U.
Tetrahedron: Asymmetry
1997,
8:
1895
12a Enders D.
Schubert H.
Nübling C.
Angew. Chem., Int. Ed. Engl.
1986,
25:
1109
12b Denmark SE.
Weber T.
Piotrowski DW.
J. Am. Chem. Soc.
1987,
109:
2224
12c Molander GA.
Chem. Rev.
1992,
29
12d Enders D.
Tiebes J.
Liebigs Ann. Chem.
1993,
173
12e Denmark SE.
Edwards JP.
Nicaise O.
J. Org. Chem.
1993,
58:
569
12f Nicaise O.
Denmark SE.
Bull. Soc. Chim. Fr.
1997,
134:
395
12g Enders D.
Nübling C.
Schubert H.
Liebigs Ann./Recl.
1997,
1089
13 Kobayashi S.
Manabe K.
Acc. Chem. Res.
2002,
35:
209
14 Yield of compound 10 increases to 81% when 4 equivalents of 8 and 0.4 M THF-H2 O (9:1) were used.
15 Recently we have found out that N ,N -dialkylhydrazones from enolizable aldehydes react with nitroalkenes, through the tautomeric ‘ene-hydrazine’ form, in the presence of thioureas as H-bonding catalysts: Pettersen, D.; Herrera, R. P.; Bernardi, L.; Fini, F.; Sgarzani, V.; Fernández, R.; Lassaletta, J. M.; Ricci, A., Synlett 2006, in press.
16 Fernández R.
Ferrete A.
Llera JM.
Magriz A.
Martín-Zamora E.
Díez E.
Lassaletta JM.
Chem. Eur. J.
2004,
10:
737
17 These compounds proved to be rather unstable and did not resist purification by column chromatography but the crude products were obtained with a high degree of purity.
18 16 exhibits an axial N-N bond in the solid state. This characteristic has also been observed in other structures of compounds containing the 2,6-diphenylpiperidine auxiliary: Alcarazo M.
Ph.D. Thesis
University of Seville;
Seville:
2005.
19 Evans DA.
Kozlowski MC.
Murry JA.
Burgey CS.
Campos KR.
Connell BT.
Staples RJ.
J. Am. Chem. Soc.
1999,
121:
669
20 Sheldrick G.
SADABS
Bruker AXS, Inc.;
Madison, Wisconsin:
1999.
21 SIR2002: The Program , see: Burla MC.
Camalli B.
Carrozzini M.
Cascarano GL.
G iacovazzo C.
Polidori G.
Spagna R.
J. Appl. Cryst.
2003,
36:
1103
22 SHELXTL 6.14
Bruker AXS, Inc.;
Madison, Wisconsin:
2000-2003.
23 CCDC 289555 contains the supplementary crystallographic data for 16 . These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB21EZ, UK; fax: +44(1223)336033; or deposit@ccdc.cam.ac.uk].
