Onium Ylide Chemistry. 2. Methylenedialkyloxonium Ylides

Article abstract of DOI:10.1021/jo00186a006

We report evidence for the long sought after methylenedialkyloxonium ylides from methyloxonium ions by two independent routes, proving their intermediate formation through derived product analysis.Reaction of trimethyloxonium salts with sodium hydride results in competing proton abstraction besides methane formation (hydride methylation).Subsequent methylation of the formed methylenedimethyloxonium ylide by excess trimethyloxonum ion is resulting in C₁ --> C₂ conversion and formation of dimethylethyloxonium ion which with sodium hydride gives ethane (and methane) or by β-elimination ethylene.Besides expected fluoride alkylation products, i.e., alkyl fluorides and fluorosilanes, fluoride-induced desylilation of dimethyl((trimethylsilyl)methyl)oxonium tetrafluoroborate also results in the formation of methylenedimethyloxonium ylide giving via subsequent methylation and cleavage methyl ethyl ether and ethyl fluoride.