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cant modularity with respect to the reactive functional
groups of the reagents while requiring little change to
the reaction conditions employed (temperature, time,
catalyst loading, etc.) Numerous combinations for di-
rectly coupling alkynes or methyl ketones with alco-
hols and aldehydes are now possible and the method-
ologies reported herein are expected to be of value
for the preparation of chalcones and related com-
pounds, particularly in a combinatorial manner.[18] In
a broader perspective, these results establish GOꢁs po-
tential for use in synthetic chemistry, especially in the
development of metal-free methodologies, rather than
simply as a precursor to graphene and derivatives
thereof.[1] Future efforts will be directed toward opti-
mizing the reactions described herein and further ex-
ploring the as yet unknown factors that contribute to
GOꢁs remarkable reactivity (e.g., extent of oxidation,
surface area, etc.)
[6] D. E. Fogg, E. N. dos Santos, Coord. Chem. Rev. 2004,
248, 2365–2379.
[7] A. Hamwi, V. Marchand, J. Phys. Chem. Solids 1996,
57, 867–872.
[8] All chalcone products described exhibited an E olefin
1
configuration, as determined by H NMR spectroscopy.
Experimental Section
[9] Similar results were obtained using GO prepared using
the Staudenmaier method.[19]
General Procedure for the Synthesis of 1 from a
Methyl Ketone or Alkyne and an Aldehyde or
Alcohol
[10] a) J. Zhang, X. Liu, R. Blume, A. Zhang, R. Schlçgl,
D. S. Su, Science 2008, 322, 73–77; b) T.-F. Yeh, J.-M.
Syu, C. Cheng, T.-H. Chang, H. Teng, Adv. Funct.
Mater. 2010, 20, 2255–2262.
In a typical preparation, a 7.5-mL vial was charged with 50–
200 mg of GO, methyl ketone or alkyne (0.5 mmol), alde-
hyde or alcohol (0.5 or 1 mmol) and a magnetic stir bar. The
vial was then sealed with a Teflon-lined cap under ambient
atmosphere and heated at 80–1508C for 14–24 h. Afterward,
the reaction mixture was cooled to room temperature and
washed with 50 mL of CH2Cl2. The filtrate was collected
and the solvent was evaporated to obtain the crude product.
Following purification of the crude product by column chro-
matography on silica gel, the desired product was dried
under vacuum and characterized.
[11] The GO employed was measured to have a specific sur-
face area of 1.138 m2 gÀ1 using the BET method.[20] No
significant change in surface area was observed when
the recovered catalyst was analyzed.
[12] The carbon materials recovered after the alcohol oxida-
tion reactions were found to be reduced by FT-IR anal-
ysis,[21] and were successfully re-oxidized using the
aforementioned methods[5] and reused without signifi-
cant changes in activities.
[13] a) F. Alonso, P. Riente, M. Yus, Eur. J. Org. Chem.
2008, 4908–4914; b) S. Kim, S. W. Bae, J. S. Lee, J.
Park, Tetrahedron 2009, 65, 1461–1466.
[14] Because the GO was serving in multiple roles in this
reaction, higher loadings were employed to maximize
the formation of product.
Acknowledgements
[15] When 4-tert-butylphenylacetylene was treated with
benzaldehyde and GO, the formation of coupling prod-
uct 2 (and not 3) was observed. This result suggested to
us that the reaction proceeded via hydration of the
alkyne, followed by Claisen–Schmidt condensation of
the methyl ketone with the aldehyde, rather than hy-
droacylation.
We gratefully acknowledge support for this work provided by
the National Science Foundation (grant no. DMR-0907324)
and the Robert A. Welch Foundation (grant No. F-1621).
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