New Convenient Synthesis of β,β-Difluoro Amines and β,β-Difluoro-α-amino Acid Alkyl Esters by the Addition of Hydrogen Fluoride to 1-Azirines

Article abstract of DOI:10.1021/jo01314a024

The reaction of hydrogen fluoride in pyridine solution with a series of substituted 1-azirines (1) was investigated. β,β-Difluoro amines (4) were obtained in good yields.The exceptions are the cases of 2-phenyl-3-methyl-1-azirine (1b) and 2,3-diphenyl-1-azirine (1c) for which the direct formation of a stabilized carbocation (6) from the azirinium ion 2 is probable.The former gave 54 percent of a pyrazine (11b) and 5 percent of α-fluoropropiophenone (9b) along with 20 percent of difluoro amine 4b, while the latter afforded only the corresponding α-fluoro ketone (9c).A mechanism is suggested.