859499-99-3Relevant academic research and scientific papers
Study of the ESI-mass spectrometry ionization mechanism of Fischer carbene complexes
Wulff, William D.,Korthals, Keith A.,Martinez-Alvarez, Roberto,Gomez-Gallego, Mar,Fernandez, Israel,Sierra, Miguel A.
, p. 5269 - 5277 (2005)
By means of deuterium-labeling experiments, we have carried out a systematic ESI-MS study to determine the mechanism of ESI ionization of alkenyl and alkynyl group 6 Fischer carbene complexes. These compounds can be ionized under ESI conditions only in the presence of additives such as hydroquinone (HQ) or tetrathiafulvalene (TTF). Our results demonstrate that in the ESI source an anion-radical is formed after the initial HQ- or TTF-mediated electron transfer to the metallic carbene complex. For alkenyl carbene complexes, this species evolves by extrusion of a hydrogen radical to form an allenylchromium anion that is detected as the [M - H]- ion in the mass spectrum. The preference for this mechanistic pathway could be rationalized by DFT calculations. In the case of alkynyl carbene complexes, experiments combining deuterated substrate, additive, and solvent demonstrate that the previously proposed allene-anion carbene complex is not formed. Instead, the H transfer from the ethoxy group in the anion radical, followed by extrusion of a hydrogen radical, leads to an allenyl anion that is detected in the ESI-MS as [M - H - CO]-.
Practical thiol surrogates and protective groups for arylthiols for Suzuki-Miyaura conditions
Itoh, Takahiro,Mase, Toshiaki
, p. 2203 - 2206 (2007/10/03)
We have developed practical thiol surrogates and arylthiol protective groups for the Suzuki-Miyaura reaction. 2-Ethylhexyl-3-mercaptopropionate and 4-(2′-mercaptoethyl)pyridine were shown to be not only good thiol surrogates but also good protective groups for thiol. We have demonstrated toleration of these protective groups under aqueous Suzuki-Miyaura conditions.
