Observation and Iodine Oxidation of the Protonated Anionic Propargyltungsten Species Formed in the Reaction of Fischer-Type Carbene Complexes with Alkynyllithiums
Variable-temperature NMR studies of the reaction of anionic propargyltungstenspecies with methanol were carried out. On protonation, 1,2-migration of the metal group occurred to generate a vinylmetal species, which was stable up to 0 °C. Furthermore, iodine oxidation of the reaction intermediates gave one of several types of oxidized products, depending on the procedure used.
The synthesis of β-keto Fischercarbenecomplexes is reported. Deprotonation of alkyl Fischercarbenecomplexes followed by acylation of the resulting metal enolates with acid chlorides yielded β-keto carbenecomplexes in yields up to 50%. The complexes were relatively stable and could be characterized spectroscopically. Upon treatment with bases such as pyridine, these complexes produced β-methoxy