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.
Iridium-catalyzed hydrosilylation of tertiary amides followed by acid-mediated condensation with active methylene compounds provides multifunctionalized non-N-containing products. This scalable method is broad in scope and shows remarkable chemoselectivity for the amide group in the presence of functionalities such as ester, cyano, nitro, silyl dienol ether, and ketone.
D.-P. Wu, W. Ou, P.-Q. Huang, Org. Lett., 2022, 24, 5366-5371.
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.