Mechanistic insights into the gold(I)-catalyzed annulation of propiolates with isoxazoles: a DFT study
Abosede Adejoke Ogunlana and Xiaoguang Bao *（鲍晓光）
College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
Chem. Commun.,2019, 55, 11127--11130
The detailed mechanisms of gold(I)-catalyzed annulations of propiolates with substituted and unsubstituted isoxazoles were investigated by DFT calculations. A unified rationale for the formation of the key seven-membered heterocyclic intermediate was proposed through initial chemoselective N-attack of isoxazole followed by sequential generation of an unprecedented 2H-azirine-containing intermediate, 6p electrocyclization and ring expansion. Subsequent substrate-dependent transformations were rationalized to generate the divergent products. The origins of the chemo- and regioselectivities coupled with the factors responsible were addressed.