2-Monosubstituted 1,3-dioxolanes and dithiolanes act as hydride-releasing fragments, transferring intramolecularly their acetalic H atom to the central carbon of ketenimine functions. The presumed products of these migrations, o-quinomethanimines, undergo in situ 6 pi-electrocyclization. A computational study supports this mechanism and the hydride-shift character of the first step. Carbodiimides were also suitable substrates, although less reactive.
Scandium triflate as a recyclable catalyst for chemoselective thioacetalization
作者:Ahmed Kamal、Gagan Chouhan
DOI:10.1016/s0040-4039(01)02378-4
日期:2002.2
Scandium triflate [Sc(OTf)(3)] has been found to be an extremely efficient and recyclable catalyst for the addition of ethanethiol, 1,2-ethanedithiol and 1,3-propanedithiol to both aromatic and aliphatic aldehydes. In addition, by employing this catalyst, high chemoselective thioacetalization of carbonyl compounds has been achieved. (C) 2002 Elsevier Science Ltd. All rights reserved.