The reaction was quenched (NH Cl solution) and worked up in the normal
4
way to afford pure 3 after silica chromatography (see electronic supporting
information for details).
8 Use of PhZnCl in Rh-catalysed 1,4-additions: (a) N. Tokunaga and
T. Hayashi, Tetrahedron: Asymmetry, 2006, 17, 607; (b) A. Kina,
K. Ueyama and T. Hayashi, Org. Lett., 2005, 7, 5889 and references
therein. Recently, a single example of an asymmetric 1,2-addition of
PhZnCl was reported as a by-product (17% yield, 36% ee) in a 1,4 study;
(c) N. Tokunaga and T. Hayashi, Tetrahedron: Asymmetry, 2006, 17,
607–613.
§
A modified transition state where the carbonyl oxygen is coordinated to
…
the aluminium (i.e. an additional O Al contact in C) is also consistent
with the present experimental data and predicts the same stereochemical
outcome.
"
Equimolar solutions of PhZnBr and AlMe
3
were mixed. Ambient
temperature C NMR spectra indicated the presence of two, time averaged
broad methyl signals (d 27.8, 210.4) assigned to mixtures of species
9 Use of RZnBr in asymmetric Negishi couplings: (a) F. O. Arp and
G. C. Fu, J. Am. Chem. Soc., 2005, 127, 10482; (b) C. Fischer and
G. C. Fu, J. Am. Chem. Soc., 2005, 127, 4594.
13
C
containing both AlMe and ZnMe. Analysis of the phenyl region is
complicated by the low intensity of the ipso-Ph signals and the presence of
secondary exchanges.
10 Use of IZnCH CO R in asymmetric Reformansky reactions:
2
2
P. G. Cozzi, Angew. Chem., Int. Ed., 2007, 46, 2568 and references
therein.
1 A. J. Blake, J. Shannon, J. C. Stephens and S. Woodward, Chem.–Eur.
1
J., 2007, 13, 2462.
2 C. Bolm, N. Hermanns, J. P. Hildebrand and K. Mu n˜ iz, Angew. Chem.,
1
Reviews: (a) V. Dimitrov and K. Kostova, Lett. Org. Chem., 2006, 3,
76; (b) L. Pu and H.-B. Yu, Chem. Rev., 2001, 101, 757; (c) Organozinc
1
1
Int. Ed., 2000, 39, 3465.
13 Specifically, using ent-L1 (i.e. 2R configuration) ZnEt
Reagents, ed. P. Knochel and P. Jones, Oxford University Press,
Oxford, UK, 1999.
2
adds to the Si
2
3
4
5
Date of search: 6 June 2007 [ZnC* + HC(LO)C* to give an alcohol
product; an asterisk indicates a position of free valency].
Review of B–Zn exchange: E. Hupe, M. I. Calaza and P. Knochel,
J. Organomet. Chem., 2003, 680, 136.
(a) Review of Zr–Zn exchange: P. Wipf and C. Kendall, Chem.–Eur. J.,
2002, 8, 1778.
(a) Direct I–Zn exchange: P. Knochel, in Handbook of Organopalladium
Chemistry for Organic Synthesis, ed. E. Negishi, John Wiley & Sons,
Inc., Hoboken, USA, 2002, Vol. 1, pp. 1651–1659; see also pp. 77–99 in
reference 1c; (b) Li–Zn exchange: J. G. Kim and P. J. Walsh, Angew.
Chem., Int. Ed., 2006, 45, 4175; (c) Mg–Zn exchange: J. L. von
dem Bussche-Hunnefeld and D. Seebach, Tetrahedron, 1992, 48, 5719.
Over 200 different commercial RZnX reagents are available, see:
www.sial.com.
(a) Review: E. Negishi, X. Zeng, Z. Tan, M. Qian, Q. Hu and Z. Huang,
in Metal-Catalyzed Cross-Coupling Reactions, ed. A. De Meijere and
F. Diederich, Wiley-VCH, Weinheim, Germany, 2nd edn, 2004, Vol. 2,
pp. 815–889; (b) the use of RZnX reagents in other processes, e.g.
carbometallation, has been reported, see: E. Lorthiois, I. Marek and
J. F. Normant, J. Org. Chem., 1998, 63, 566 and references therein.
face of PhCHO and ZnPh adds to the Si face of 4-MeOPhCHO. In all
2
these cases (and those of Scheme 1) the CIP priority of the incoming
nucleophile is less than that of the aldehyde substituent. (a) I. Sato,
T. Saito and K. Soai, Chem. Commun., 2000, 2471; (b) K. Soai,
Y. Kawase and A. Oshio, J. Chem. Soc., Perkin Trans. 1, 1991, 1613.
14 B. Wu and H. S. Mosher, J. Org. Chem., 1986, 51, 1904.
15 (a) Review: P. Knochel, W. Dohle, M. Gommermann, F. F. Kneisel,
F. Kop, T. Korn, I. Sapountzis and V. A. Vu, Angew. Chem., Int. Ed.,
2003, 42, 4302; (b) Selected recent result: X. Wang, X. Sun, L. Zhang
and Y. Xu, Org. Lett., 2006, 8, 305. It is the presence of polar solvent
additives and/or the presence of lithium cations which is often
detrimental to secondary asymmetric processes; (c) For a very recent
successful application see: A. Alexakis, S. El Hajjaji, D. Polet and
X. Rathgeb, Org. Lett., 2007, 9, 3393.
16 T. Rasmussen and P.-O. Norrby, J. Am. Chem. Soc., 2001, 123, 2464
and references therein.
17 I. Shiina, K. Konishi and Y. Kuramoto, Chem. Lett., 2002, 164. These
studies were carried out with ent-L2 (i.e. 2R configuration).
18 K. Biswas, O. Prieto, P. Goldsmith and S. Woodward, Angew. Chem.,
Int. Ed., 2005, 44, 2232.
6
7
This journal is ß The Royal Society of Chemistry 2007
Chem. Commun., 2007, 3945–3947 | 3947