A Facile Preparation of N-(Isopropoxyalkyl) Amides by Generation and Trapping of N-Acyliminium Ions from Ionization-Rearrangement Reactions of N-Triflyloxy Amides
摘要:
A series of hydroxamic acids were converted to N-triflyloxy amides which were heated in 2-propanol to give N-(1-isopropoxyalkyl) amides in high yields. The method is simple, direct, and extremely tolerant of structural diversity both in the N-acyl group, as well as in the 1-isopropoxyalkyl group. N-Alkylation of secondary N-(1-isopropoxyalkyl) amides can be used for converting them to tertiary N-(1-isopropoxyalkyl) amides. N-Acyliminium ions of wide structural diversity can be generated easily from N-(1-isopropoxyalkyl) amides available by this methodology.
Condition-dependent transformations between hydroximic acids and thioaceticacid were achieved. Using NH4HCO3 in the ethanol solvent, efficient N–O bond cleavage of hydroxamic acids occurred to afford primary amides with high functional group compatibility. The reaction was switched to O-acylation when NEt3 and H2O were used as the base and solvent, respectively. These facile transformations could