A novel approach of cycloaddition of difluorocarbene to α,β-unsaturated aldehydes and ketones: synthesis of gem-difluorocyclopropyl ketones and 2-fluorofurans
作者:Wei Xu、Qing-Yun Chen
DOI:10.1039/b212232d
日期:2003.3.27
acetals and ketals are easily obtained in moderate yields from the [1 + 2] cycloaddition of difluorocarbene to 1,3-dioxolanes of alpha,beta-unsaturated aromatic aldehydes and ketones. Hydrolysis of these fluorinated compounds under acidic conditions either gives the corresponding gem-difluorocyclopropyl ketones or 1-aryl-2-fluorofuran derivatives through intramolecular carbonium rearrangement with simultaneous
Aldehydes were efficiently transformed into allylic dioxolanes by a Wittig-type reaction, using 1,3-dioxolan-2-yl-methyltriphenylphosphonium bromide under phase transfer conditions. The substituent kinetic effects were studied, and related to Hammett values and electrochemical potentials. (C) 1998 Elsevier Science Ltd. All rights reserved.
Asymmetric C–H insertion of Rh(II) stabilized carbenoids into acetals: A C–H activation protocol as a Claisen condensation equivalent
作者:Huw M.L. Davies、Jaemoon Yang、Joachim Nikolai
DOI:10.1016/j.jorganchem.2005.08.026
日期:2005.12
The dirhodium tetraprolinate, Rh-2(S-DOSP)(4) is an efficient catalyst in an enantio selective C-H activation protocol. Rh-2(S-DOSP)(4) catalyzed decomposition of aryldiazoacetates or vinyldiazoacetates results in the formation of transient rhodium carbenoid intermediates. These inter-mediates are capable of selectively inserting into the C-H bond of acetals. The resulting products are protected P-keto esters, and so the C-H activation protocol can be considered as strategically equivalent to the Claisen condensation. (c) 2005 Elsevier B.V. All rights reserved.