Journal of the American Chemical Society
ARTICLE
(6) Clark, J. H. Chem. Rev. 1980, 80, 429–452.
is frequently used as a measure of inductive effects in substituted
benzene rings even if the substituent is not meta to the reactive
center. See: (a) Wheeler, S. E.; Houk, K. N. J. Am. Chem. Soc. 2008,
130, 10854–10855. (b) Wheeler, S. E.; McNeil, A. J.; M€uller, P.; Swager,
T. M.; Houk, K. N. J. Am. Chem. Soc. 2010, 132, 3304–3311.
(25) Pedragosa-Moreau, S.; Morisseau, C.; Zylber, J.; Archelas, A.;
Baratti, J.; Furstoss, R. J. Org. Chem. 1996, 61, 7402–7407.
(26) (a) Laird, R. M.; Parker, R. E. J. Am. Chem. Soc. 1961,
83, 4277–4281. (b) Blumenstein, J. J.; Ukachukwu, V. C.; Mohan,
R. S.; Whalen, D. L. J. Org. Chem. 1993, 58, 924–932. In contrast, ring-
opening reactions that follow a SN1-like pathway favor internal opening
and have large negative F values that correlate to σp.
(27) Ring opening by fluoride is irreversible under the reaction
conditions; thus, the ring-opening step (in which a prochiral epoxide is
transformedintochiralfluorohydrin, or in which one enantiomer of racemic
epoxide reacts selectively) is inherently the enantiodetermining step.
(28) Since the ee of the product changes over the course of kinetic
resolutions, a direct comparison of eeproduct vs eecat is not meaningful. See:
Johnson, D. W.; Singleton, D. A J. Am. Chem. Soc. 1999, 121, 9307–9312.
(29) Blackmond, D. G. J. Am. Chem. Soc. 2001, 123, 545–553.
(30) Blackmond, D. G. Acc. Chem. Res. 2000, 33, 402–411.
(31) For examples involving negative nonlinear effects and rate
amplification, see: (a) Kina, A.; Iwamura, H.; Hayashi, T. J. Am. Chem.
Soc. 2006, 128, 3904–3905. (b) Duan, W.-L.; Iwamura, H.; Shintani, R.;
Hayashi, T. J. Am. Chem. Soc. 2007, 129, 2130–2138. For an example
involving positive nonlinear effects and rate suppression, see: (c) Yamagiwa,
N.; Qin, H.; Matsunaga, S.; Shibasaki, M. J. Am. Chem. Soc. 2005,
127, 13419–13427.
(7) Kalow, J. A.; Doyle, A. G. J. Am. Chem. Soc. 2010, 132, 3268–3269.
(8) Katcher, M. H.; Doyle, A. G. J. Am. Chem. Soc. 2010, 132,
17402–17404. This report describes the palladium-catalyzed asym-
metric synthesis of allylic fluorides through SN2 attack of fluoride on a
π-allyl intermediate.
(9) (a) Bruns, S.; Haufe, G. J. Fluorine Chem. 2000, 104, 247–254.
(b) Haufe, G.; Bruns, S. Adv. Synth. Catal. 2002, 344, 165–171.
(10) Olah, G. A.; Welch, J. T.; Vankar, Y. D.; Nojima, M.; Kerekes, I.;
Olah, J. A. J. Org. Chem. 1979, 44, 3872–3881.
(11) Jacobsen, E. N. Acc. Chem. Res. 2000, 33, 421–431.
(12) (a) Hansen, K. B.; Leighton, J. L.; Jacobsen, E. N. J. Am. Chem.
Soc. 1996, 118, 10924–10925. (b) Konsler, R. G.; Karl, J.; Jacobsen, E. N.
J. Am. Chem. Soc. 1998, 120, 10780–10781.
(13) Nielsen, L. P. C.; Stevenson, C. P.; Blackmond, D. G.; Jacobsen,
E. N. J. Am. Chem. Soc. 2004, 126, 1360–1362.
(14) A number of oligomeric analogues of 2 have been discovered
that serve as excellent catalysts in ring-opening reactions by favoring
cooperative bimetallic interactions. For reviews, see: (a) Zhu, X.;
Venkatasubbaiah, K.; Weck, M.; Jones, C. W. ChemCatChem 2010,
2, 1252–1259. (b) Haak, R. M.; Wezenberg, S. J.; Kleij, A. W. Chem.
Commun. 2010, 46, 2713–2723.
(15) Blackmond, D. G. Angew. Chem., Int. Ed. 2005, 44, 4302–4320.
1
(16) Unlike H NMR, 19F NMR does not suffer significant peak
broadening in the presence of (salen)Co(III). Furthermore, 19F NMR
allowed the reaction to be performed in TBME, which is not readily
available as TBME-d12.
(17) Oxidation occurs readily in the presence of air and acid:
Jacobsen, E. N.; Kakiuchi, F.; Konsler, R. G.; Larrow, J. F.; Tokunaga,
M. Tetrahedron Lett. 1997, 38, 773–776. Additionally, (1) reactions
conducted under a N2 atmosphere exhibited an extended induction
period, and (2) product added to the reactions did not affect the reaction
rates, eliminating the possibility of product autocatalysis. See Supporting
Information.
(18) However, 4 decomposes over time to the catalytically inactive
lactam 40 (shown below) when exposed to ambient moisture. Therefore,
commercial 4 should be distilled from CaH2 and stored over activated 3
Å molecular sieves: Shaw, T. W.; Kalow, J. A.; Doyle, A. G. Org. Synth.
2012, 89, 9–18. Chiral isothiourea 3 does not exhibit hydrolysis under
ambient conditions.
(32) Girard, C.; Kagan, H. B. Angew. Chem., Int. Ed. 1998, 37,
2922–2959.
(33) K is a property of the catalyst and should be independent of the
substrate (for an exception, see Kitamura, M.; Suga, S.; Oka, H.; Noyori, R.
J. Am. Chem. Soc. 1998, 120, 9800–9809), but g is dependent on substrate.
(34) For a schematic explanation, see Scheme S1 (Supporting
Information).
(35) For an example in the Sharpless asymmetric epoxidation, see:
Puchot, C.; Samuel, O.; Dunach, E.; Zhao, S.; Agami, C.; Kagan, H. B.
J. Am. Chem. Soc. 1986, 108, 2353–2357.
(36) Nielsen, L. P. C. Ph.D. Thesis, Harvard University, 2006.
(37) (a) Wu, M. H.; Hansen, K. B.; Jacobsen, E. N. Angew. Chem., Int.
Ed. 1999, 38, 2012–2014. (b) Nakano, K.; Hashimoto, S.; Nozaki, K.
Chem. Sci. 2010, 1, 369–373. In the latter case, a heterochiral adipate-
bridged catalyst was found to be optimal.
(38) 8 does not undergo aerobic oxidation readily at these catalyst
loadings under the standard reaction conditions; t-BuOOH promotes
immediate oxidation without detrimental effects on yield or ee.
(39) An acetylated, C1-symmetric monomeric catalyst promotes
reaction more slowly than 2 does, suggesting that the rate acceleration
is not due to the electronic differences in the dicarboxylate-linked 8.
(40) The fluoride ring opening of (()-hexene oxide catalyzed by 2
also exhibits a first-order dependence on [2], consistent with the kinetic
data obtained using (R)-5; see Supporting Information.
(41) For representative examples, see: (a) Ng Cheong Chan, Y.;
Osborn, J. A. J. Am. Chem. Soc. 1990, 112, 9400–9401. (b) Mccleland,
B. W.; Nugent, W. A.; Finn, M. G. J. Org. Chem. 1998, 63, 6656–6666.
(c) Bandini, M.; Cozzi, P. G.; Umani-Ronchi, A. Tetrahedron 2001,
57, 835–843. (d) Rosner, T.; Le Bars, J.; Pfaltz, A.; Blackmond, D. G.
J. Am. Chem. Soc. 2001, 123, 1848–1855. (e) ref 31a. In (b) and (c),
resting-state tetramers and an active dimeric catalyst are proposed.
(42) A conceptually analogous scenario, for an enzymatic reaction
that exhibits overall first-order kinetics but is experimentally determined
to be bimolecular, has been described: Baker, G. M.; Weng, L. J. Theor.
Biol. 1992, 158, 221–229.
(19) We found that benzoyl fluoride stored under air undergoes slow
hydrolysis to provide small quantities of benzoic acid; the presence of
this impurity reduced reaction rates. Therefore, in these experiments, we
employed purified benzoyl fluoride. For synthetic applications, however,
this precaution is not necessary. See Supporting Information for details.
(20) Alternatively, unproductive H-bonding interactions between
HFIP and various Lewis basic components of the reaction could account
for this rate inhibition. HFIP is well known to have unique properties as a
solvent and additive: Shuklov, I. A.; Dobrovina, N. V.; B€orner, A.
Synthesis 2007, 2925–2943.
(21) Hammett, L. P. J. Am. Chem. Soc. 1937, 59, 96–136.
(22) All of the substrates employed react selectively under these
conditions, confirming that unselective background reaction is not res-
ponsible for the differences in rate. Selectivity factor s is calculated here from
the conversion (C) and ee (ee) of epoxide: s = ln[(1 ꢀ C)(1 ꢀ ee)]/
ln[(1 ꢀ C)(1 + ee)]. For a discussion of kinetic resolutions, see: Keith,
J. M.; Larrow, J. F.; Jacobsen, E. N. Adv. Synth. Catal. 2001, 343, 5–26.
(23) Hammet constants σm were obtained from: Speight, J. G. In
Lange’s Handbook of Chemistry, 16th ed.; McGraw-Hill: New York, 2005;
Chapter 2.19, pp 2.702ꢀ2.709. For Hammett correlations of the rate
data using other σ constants, see the Supporting Information.
(24) It is expected that ring opening at the terminal position of the
styrene oxides would be influenced primarily by inductive effects, and σm
(43) For reviews, see: (a) Murphy, E. F.; Murugavel, R.; Roesky,
H. W. Chem. Rev. 1997, 97, 3425–3468. (b) Tramꢀsek, M.; Goreshnik, E.;
ꢀ
Lozinꢀsek, M.; Zemva, B. J. Fluorine Chem. 2009, 130, 1093–1098. For a
recent example of a crystallographically characterized [CoII(μ-F)]2
complex, see: (c) Dugan, T. R.; Sun, X.; Rybak-Akimova, E. V.;
16011
dx.doi.org/10.1021/ja207256s |J. Am. Chem. Soc. 2011, 133, 16001–16012