Phosphorus in organic synthesis. The tanigawa reaction revisited as a method for converting alcohols to tertiary amines

Article abstract of DOI:10.1016/S0040-4039(98)01316-1

Contrary to earlier observations, N-methyl-N- phenylaminotriphenylphosphonium iodide 1 (the Murahashi reagent) does not react with alcohols and primary or secondary amines under mild conditions (80°) to give secondary or tertiary amines. However the reaction can be successfully performed at higher temperatures. A mechanistic scheme implying initial amine exchange between 1 and the added amine leading to the N,N- dimethyl analog 5 is suggested. An improved synthesis where the reactive intermediate 5 is formed in situ from triphenylphosphine, carbon tetrachloride and HNR³R⁴ is described.