References
<A NAME="RG0440203TX-1">1</A> For an excellent compilation
of catalytic, enantioselective processes see: Comprehensive
Asymmetric Catalysis
Jacobsen EN.
Pfaltz A.
Yamamoto H.
Springer;
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For reviews see:
<A NAME="RG0440203TX-2A">2a</A>
Palomo C.
Oiarbide M.
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Johnson JS.
Evans DA.
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<A NAME="RG0440203TX-2D">2d</A>
Carreira EM.
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Yamamoto H.
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<A NAME="RG0440203TX-2E">2e</A>
Gröger H.
Vogel EM.
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Yoshikawa N.
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List B.
Lerner RA.
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<A NAME="RG0440203TX-4B">4b</A> Review:
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Synlett
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Trost BM.
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<A NAME="RG0440203TX-9A">9a</A>
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<A NAME="RG0440203TX-9B">9b</A>
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<A NAME="RG0440203TX-10">10</A>
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A slightly different approach
was pursued by Feringa, Alexakis, and Krische who investigated catalytic, enantioselective
conjugate additions to enones followed by a diastereoselective aldol
reaction, see:
<A NAME="RG0440203TX-11A">11a</A>
Feringa BL.
Pineschi M.
Arnold LA.
Imbos R.
de
Vries AHM.
Angew. Chem.,
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2620 ; Angew. Chem. 1997, 109, 2733
<A NAME="RG0440203TX-11B">11b</A>
Alexakis A.
Trevitt GP.
Bernardinelli G.
J.
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<A NAME="RG0440203TX-11C">11c</A>
Cauble DF.
Gipson JD.
Krische MJ.
J. Am. Chem. Soc.
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1110
<A NAME="RG0440203TX-12">12</A>
Mascarenhas CM.
Miller SP.
White PS.
Morken JP.
Angew.
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<A NAME="RG0440203TX-13">13</A>
Schneider C.
Hansch M.
Chem. Commun.
2001,
1218
<A NAME="RG0440203TX-14A">14a</A>
Simpura I.
Nevalainen V.
Angew.
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Nevalainen V.
Simpura I.
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<A NAME="RG0440203TX-15">15</A> Evans et al. have established
metal-catalyzed, highly anti-diastereoselective
Tishchenko reductions of β-hydroxy ketones, see:
Evans DA.
Hoveyda AH.
J.
Am. Chem. Soc.
1990,
112:
6447
<A NAME="RG0440203TX-16">16</A> For a comprehensive review about
synthesis and various applications of tartaric acid-derived TADDOLs
as chiral ligands and auxiliaries see:
Seebach D.
Beck AK.
Heckel A.
Angew.
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<A NAME="RG0440203TX-17">17</A>
All new products were fully characterized
by 1H and 13C NMR,
IR, MS and elemental analysis. Representative spectroscopic data: 3a: [α]D
20 = +8.9° (c = 1.0, CHCl3, 47% ee);
IR (film): 3452, 2969, 2936, 2878, 1731, 1272, 1202, 1163, 1072
cm-1; 1H (200 MHz,
CDCl3): δ = 0.94 (d, J = 7.0 Hz,
6 H, i-Pr), 1.19 (d, J = 7.0
Hz, 3 H, CH3) 1.22 (d, J = 7.0 Hz,
6 H, i-Pr), 1.56 (m, 2 H, CH2),
1.81 [m, 1 H, CH(CH3)2], 2.61 [sept, J = 7.0 Hz, 1 H, CH(CH3)2],
3.02 (br s, 1 H, OH), 3.58 (m, 1 H, CHOH),
4.88 (m, 1 H, CHOCOR); 13C
(50 MHz, CDCl3): δ = 17.61, 18.87,
19.14, 19.23, 22.91, 32.16, 34.39, 41.61, 63.25, 75.49, 178.6; MS
(200 eV, DCI/NH3): m/z = 422(1) [2M + NH4
+],
237(3) [M + NH3 + NH4
+], 220(100) [M + NH4
+],
202(8) [M + H+];
Calculated for C11H22O3 (202.29):
C 65.31, H 10.96; Found C 65.22, H 11.02; 10b: [α]D
20 = +11.5 (c = 0.85, CHCl3,
57% ee); IR (film): 3518, 2967, 2876, 1714, 1389, 1267,
1204, 1163, 1070, 1011 cm-1; 1H
(200 MHz, CDCl3): δ = 0.89 (s, 9 H, t-Bu), 0.93 (d, J = 7.0
Hz, 6 H, i-Pr), 1.20 (d, J = 7.0 Hz, 6 H, i-Pr), 1.28-1.72 (m, 2 H, CH2),
1.75-1.95 [m, 1 H, CH(CH3)2],
2.50 (br s, 1 H, OH), 2.61 [sept, J = 7.0
Hz, 1 H, CH(CH3)2],
3.00 (dd, J = 10.5, 2.0 Hz,
1 H, CHOH), 4.95 (ddd, J = 10.5
Hz, 5.0 Hz, 2.0 Hz, 1 H, CHOCOR); 13C
(50 MHz, CDCl3): δ = 17.63, 18.97,
19.20, 19.26, 25.94, 32.37, 33.96, 34.41, 34.42, 74.73, 75.81, 178.4;
MS (200 eV, DCI/NH3): m/z = 279 (1) [M + NH3 + NH4
+],
262 (100) [M + NH4
+].
Calculated for C14H28O3 (244.37):
C 68.81, H 11.55; Found: C 69.08, 11.29.
<A NAME="RG0440203TX-18A">18a</A> The
diols derived from the aldol-Tishchenko products 3a, 3b, and 10b were
independently synthesized through anti-diastereoselective
(Me4N)BH(OAc)3-reduction of the corresponding
aldol products which were obtained according to the following references:
List B.
Lerner RA.
Barbas CF.
J. Am. Chem. Soc.
2000,
122:
2395
<A NAME="RG0440203TX-18B">18b</A> In addition see:
Trost BM.
Silcoff ER.
Ito H.
Org. Lett.
2001,
3:
2497
<A NAME="RG0440203TX-18C">18c</A> Also see:
Ramachandran PV.
Xu W.
Brown HC.
Tetrahedron Lett.
1996,
37:
4911
<A NAME="RG0440203TX-18D">18d</A> The absolute configuration
of the diol derived from 9b was assigned
based upon the known rotation value, see:
Marinetti A.
Genet J.-P.
Jus S.
Blanc D.
Ratovelomanana-Vidal V.
Chem.-Eur.
J.
1999,
5:
1160
<A NAME="RG0440203TX-18E">18e</A>
The absolute configuration
of all other products was assigned in analogy to these experiments
<A NAME="RG0440203TX-19">19</A>
The following Zr-BINOLate complexes
were tested in the reaction of 1a and 2a under otherwise identical reaction conditions:
Zr(t-BuO)4/(R)-BINOL: 31% yield (28% ee); Zr(t-BuO)4/(R)-6,6′-Br2-BINOL:
35% yield (25% ee); Zr(t-BuO)4/(R)-3,3′-Br2-BINOL:
62% yield (0% ee); Zr(t-BuO)4/(R)-3,3′-Ph2-BINOL:
89% yield (28% ee).
<A NAME="RG0440203TX-20">20</A>
Prepared by the l-proline-catalyzed
aldol addition of acetone and isobutyraldehyde according to ref.
[4]
<A NAME="RG0440203TX-21">21</A> For an excellent review about
nonlinear effects see:
Girard C.
Kagan HB.
Angew. Chem. Int. Ed.
1998,
37:
2922 ; Angew. Chem. 1998, 110, 3089