7 Trimethylsulfonium iodide is considerably less expensive than the
methylsulfate and tetrafluoroborate analogues available from Aldrich.
Their current prices in £ g−1 are 1.02, 7.48 and 74.30 respectively.
8 (a) A. Merz and G. Ma¨rk, Angew. Chem., Int. Ed. Engl., 1973, 12, 845;
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9 (a) M. E. Borredon, M. Delmas and A. Gaset, Tetrahedron Lett., 1982,
23, 5283; (b) M. E. Borredon, M. Delmas and A. Gaset, Tetrahedron,
1987, 43, 3945; (c) H. Bouda, M. E. Borredon, M. Delmas and A.
Gaset, Synth. Commun., 1987, 17, 503; (d) C. Lemini, M. Ordonez, J.
Pe´rez-Flores and R. Cruz-Almanza, Synth. Commun., 1995, 25, 2695;
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10 (a) For a similar solvent-free protocol involving t-BuOK and heating
at 60 ◦C see: F. Toda and K. Kanemoto, Heterocycles, 1997, 46, 185;
(b) F. Toda and N. Imai, J. Chem. Soc., Perkin Trans. 1, 1994, 2674.
11 (a) For examples using clean deprotonation of the salt in DMSO using
strong bases at room temperature see ref. 1b–d and: R. G. Harvey,
M. Konieczny and J. Pataki, J. Org. Chem., 1983, 48, 2930; (b) S.
Kulasegaram and R. J. Kulawiec, J. Org. Chem., 1997, 62, 6547; (c) J. A.
Ciaccio, A. L. Drahus, R. M. Meis, C. T. Tingle, M. Smrtka and
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T. Sreekanth, Tetrahedron Lett., 2006, 47, 5595.
12 (a) For useful ambient temperature reactions with the relatively expen-
sive methylsulfate salt see: P. Mosset and R. Gre´e, Synth. Commun.,
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Commun., 1990, 20, 1287; (c) M. M. Elenkov, B. Hauer and D. B.
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13 Recently efficient CC reactions in ionic liquids have been reported: S.
Chandrasekhar, C. Narasihmulu, V. Jagadeshwar and K. Venkatram
Reddy, Tetrahedron Lett., 2003, 44, 3629.
Scheme 2 Tandem epoxidation-ring opening reactions.
resulted in the isolation of the chain-extended phenyl acetaldehyde
derivative 38 in good overall yield.
In summary we have shown for the first time that appropriately
substituted N,Nꢀ-diarylureas and thioureas are capable of the
efficient catalysis of the Corey–Chaykovsky reaction involving the
inexpensive trimethylsulfonium iodide at ambient temperature.
Rather unusually, urea derivatives are clearly superior catalysts
to their thiourea analogues in these processes. These catalysed
reactions are of wide scope with respect to the aldehyde component
and clean formation of the epoxide is observed under optimal
conditions—a property which was exploited in the development
of an epoxidation–Meinwald rearrangement process which allows
convenient aromatic aldehyde homologation without requiring
intermediate purification steps. The efficient catalysis observed
in this study (5 mol% catalyst loading is generally sufficient) offers
the possibility of developing an enantioselective variant of the
reaction using chiral urea derivatives. Investigations along these
lines are under way.
14 K. Julienne, P. Metzner and V. Henryon, J. Chem. Soc., Perkin Trans.
1, 1999, 731.
15 In preliminary experiments we also found that cinnamonitrile formed
rapidly in this ylide-generating system unless water was added—a
requirement which was unlikely to be beneficial in a system involving a
hydrogen-bond donating catalyst.
Financial support from Science Foundation Ireland (SFI)
and the Irish Research Council for Science Engineering and
Technology (IRCSET) is gratefully acknowledged.
16 S. J. Connon, Chem. Commun., 2008, DOI: 10.1039/b719249e.
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18 (a) T. Okino, Y. Hoashi and Y. Takemoto, Tetrahedron Lett., 2003, 44,
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Notes and references
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(b) E. J. Corey and M. Chaykovsky, J. Am. Chem. Soc., 1962, 84, 867;
(c) V. Franzen and H.-E. Driesen, Chem. Ber., 1963, 96, 1881; (d) E. J.
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2 V. K. Aggarwal, A. Ali and M. P. Coogan, J. Org. Chem., 1997, 62,
8628.
3 (a) For recent reviews see: A.-H. Li, L.-X. Dai and V. K. Aggarwal,
Chem. Rev., 1997, 97, 2341; (b) V. K. Aggarwal and J. Richardson,
Chem. Commun., 2003, 2644; (c) V. K. Aggarwal and C. L. Winn, Acc.
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5841.
19 (a) For reports concerning the reduction of imines/reductive amination
of aldehydes/ketones using thiourea as a catalyst see: D. Menche, J.
Hassfeld, G. Menche, A. Ritter and S. Rudolph, Org. Lett., 2006, 8,
741; (b) D. Menche and F. Arikan, Synlett, 2006, 841; (c) D. Menche,
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48, 365. However, it should be noted that the role of thiourea in these
reactions has been recently brought into question, see ref. 18j.
20 F. D. Bordwell, Acc. Chem. Res., 1988, 21, 456.
21 B. Procuranti and S. J. Connon, Chem. Commun., 2007, 1421.
22 For a very recent study on the mechanism of the CC reaction see: D. R.
Edwards, P. Montoya-Peleaz and C. M. Crudden, Org. Lett., 2007, 9,
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4 (a) Representative recent examples: V. K. Aggarwal, E. Alonso, I. Bae,
G. Hynd, K. M. Lydon, M. J. Palmer, M. Patel, M. Porcelloni, J.
Richardson, R. A. Stenson, J. R. Studley, J.-L. Vasse and C. L. Winn,
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6 (a) Selected recent reviews on this topic: A. G. Doyle and E. N.
Jacobsen, Chem. Rev., 2007, 107, 5713; (b) M. S. Taylor and E. N.
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23 For other examples see ref. 17a, 18b and: P. Vachal and E. N. Jacobsen,
Org. Lett., 2000, 2, 867.
24 Both 19 and 20 are highly active catalysts in this reaction. Urea 20 was
chosen as the candidate for further study as it has already been shown
to promote a range of transformations effectively whereas 19 is less
widely used.
25 The 1H NMR spectra of the crude material after the epoxidation of o-
and p-anisaldehyde (25 and 26 respectively) indicated that the epoxides
are formed cleanly as the sole product under the reaction conditions
1342 | Org. Biomol. Chem., 2008, 6, 1339–1343
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