Categories: C=C Bond Formation >
Synthesis of substituted active methylenes
Triphenylphosphine is an efficient catalyst for a mild, solvent-free Knoevenagel condensation of aldehydes with ethyl cyanoacetate or malononitrile to afford olefins in excellent yields with (E)-geometry. This method, which is even improved by microwave irradiation, is applicable for a wide range of aldehydes.
J. S. Yadav, B. S. S. Reddy, A. K. Basak, B. Visali, A. V. Narsaiah, K. Nagaiah, Eur. J. Org. Chem., 2004, 546-551.
1,3-dicarbonyl compounds and methyl ketones or terminal aryl alkenes as simple and readily available starting materials can be efficiently converted to unsymmetrical 1,4-enediones under mild reaction conditions using a focusing domino strategy. The reaction allows an operationally simple, straightforward synthesis of various unsymmetrical 1,4-enediones.
M. Gao, Y. Yang, Y.-D. Wu, C. Deng, L.-P. Cao, X.-G. Meng, A.-X. Wu, Org. Lett., 2010, 12, 1856-1859.
A mild, palladium-catalyzed intramolecular oxidative alkylation of various ζ-alkenyl β-diketones and ζ-alkenyl β-keto esters in the presence of CuCl2 at room temperature formed the corresponding 2-cyclohexenones in high yield.
T. Pei, X. Wang, R. A. Widenhoefer, J. Am. Chem. Soc., 2003, 125, 648-649.
An efficient and regioselective Yb(OTf)3-promoted palladium-catalyzed oxidative cyclization of γ-heteroalkenyl β-keto amides has been developed. Under simple aerobic condition, various six-, seven-, and eight-membered-ring N- and O-heterocycles were obtained in excellent yield.
K.-T. Yip, J.-H. Li, O.-Y. Lee, D. Yang, Org. Lett., 2005, 7, 5717-5719.