P=N Bond Formation
FeCl2 catalyzes a facile imidization of phosphines with N-acyloxyamides to provide synthetically useful N-acyliminophosphoranes with high functional group tolerance. The transformation can be scaled up to gram scale with a catalyst loading of 1 mol%. The iminophosphoranyl moiety is an effective directing group for Rh(III)-catalyzed ortho C(sp2)-H bond amidations.
S. Lin, B. Lin, Z. Zhang, J. Chen, Y. Luo, Y. Xia, Org. Lett., 2022, 24, 3302-3306.
Amides react with NaN3 to give acyl azides in DMF at 25°C and produce the symmetrical ureas in THF/H2O at 80 °C via a sequential acyl substitution and Curtius rearrangement. All acyl azides were also obtained from secondary amides via sequential reaction with p-toluenesulfonyl chloride and NaN3. In addition, keto-stabilized iminophosphoranes can also be prepared in a one-pot reaction.
D. Joseph, S. Lee, Org. Lett., 2022, 24, 6186-6191.