Onium Ylide Chemistry. 4. Alkylhalonium Methylides

Article abstract of DOI:10.1021/ja00303a024

Alkylhalonium methylides were generated by two independent routes, proving their formation through derived product analysis.The reaction of singlet methylene, produced by photolysis of diazomethane, with methyl and ethyl halides gives in competition with C-H insertion evidence of methylenation of halogen atom, i.e., alkylhalonium methylide formation.The unstable halonium methylides are immediatly protonated or alkylated in the reaction medium to give dialkylhalonium ions which then undergo cleavage to the corresponding alkyl halides.Methyliodonium methylide was also generated via the deprotonation of dimethyliodonium hexafluoroantimonate with sodium hydride in competition with the expected methylation of fluoride and hydride, giving the major products.Subsequent methylation of the methyliodonium methylide by excess dimethyliodonium ion gives methylethyliodonium ion followed by cleavage leading to the formation of ethyl halides and via hydride reduction to ethane, respectively.Attempted formation of alkylhalonium methylides via fluoride cleavage of methyl<(trimethylsilyl)methyl>halonium hexafluoroantimonates was unsuccessful due to ready disproportionation of the halonium ions.