ABSTRACT
With Et3N·3HF as the fluorination reagent, (IPr)CuF-catalyzed α-site regiocontrolled trans-hydrofluorination of ynamides has been achieved, affording (Z)-α-fluoroenamides in moderate to excellent yields. It was interesting to note that the regioselectivity of the reaction is reversed to that observed in the (Ph3P)3CuF-catalyzed hydrofluorination of ynamides. Additionally, a variety of different ynamides including oxazolidinonyl-, imidazolyl-, and N-sulfonyl ynamides were suitable for the reaction system and the subsequent oxidation of the fluorinated products enables a convenient synthesis to α-fluoroimides.
ABSTRACT
With Et3N·3HF as the fluorinating reagent, a copper(I)- or silver(I)-catalyzed ß/α-site-regiocontrolled trans-hydrofluorination of alkynamides has been achieved, affording the corresponding fluoro enamides in moderate to nearly quantitative yields with high regio- and stereoselectivity, respectively. The reaction proceeds under mild reaction conditions and exhibits good functional group tolerance. Further, the deuterium-labeling experiment confirmed the existence of the alkenylcopper intermediate.
ABSTRACT
A mild and efficient methodology involving Pd(PPh3)4-catalyzed intramolecular cyclization of N-alkynyl alkyloxycarbamates with CuCl2 or CuBr2 for the synthesis of 4-halo-oxazolones was developed. This reaction exhibiting good functional tolerance provided a new, efficient, and rapid synthetic process to 4-halo-oxazolones. The resulting 4-halo-oxazolones can serve as great potential precursors for the 3,4,5-trisubstituted oxazolones via a Pd-catalyzed cross-coupling reaction.
