3
À
Lewis Acid-Catalyzed Conjugate Addition of sp C H Bonds to Methylenemalononitriles
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Figure 1. X-ray crystal structure of 3fa.
ture of these products was further confirmed by X-ray
crystallographic analysis of product 3fa (Figure 1).[13]
In summary, we have successfully developed the
direct conjugate addition of 2-alkylazaarenes to meth-
ylenemalononitriles to afford heterocycle-containing
À
nitriles via C H bond functionalization. The
Yb
A
À
catalyst for this C H functionalization reaction. This
protocol provides an efficient synthetically useful ap-
proach for transformation of azaarenes to valuable
medicinal heterocycles.
Experimental Section
[3] a) A. R. Katritzky, C. A. Ramsden, E. F. V. Scriven,
R. J. K. Taylor, Comprehensive Heterocyclic Chemistry,
Elsevier, Oxford, 2008, Vol. 7; b) G. D. Henry, Tetrahe-
dron 2004, 60, 6043; c) J. P. Michael, Nat. Prod. Rep.
2005, 22, 627.
Typical Procedure
Under argon, YbACHTUNGTRENNUNG(OTf)3·XH2O (9.3 mg, 5 mol%), 2,6-luti-
dine 1a (0.75 mmol), 2-benzylidenemalononitrile 2a
(0.30 mmol), and dry dioxane (1.5 mL) were added to the
screw cap vial. The mixture was kept stirring at 1208C and
monitored by TLC, after 24 h, the solvent was evaporated
under reduced pressure and the residue was purified by
flash column chromatography on a silica gel to give the de-
sired product 3aa.
À
[4] For selected examples on C H functionalization of
azaarenes, see: a) E. J. Moore, W. R. Pretzer, T. J.
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Acknowledgements
Financial support provided by the National Natural Science
Foundation of China (21172226 and 21133011) and Chinese
Academy of Sciences is gratefully acknowledged.
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