posted on 2024-01-25, 14:03authored byXuanyu Zhu, Yi Li, Hongtao Luo, Jing Li, Yuhui Hua, Guohua Liu, Lingling Li, Rui Liu
The propargylic dialkyl effect (PDAE) has a significant
impact
on the cyclization reaction of enynes, partly reflected in changing
the types of products. Herein, we described the influence of the propargylic
dialkyl effect on the Ir(III)-catalyzed cycloisomerization of 1,6-enynes
to provide strained cyclobutenes. A series of substituted 1,6-enynes
were proved to be excellent substrate candidates in the presence of
[Cp*IrCl2]2 in toluene. Mechanistic investigation,
based on deuterium labeling experiments and control experiments, indicated
that the propargylic dialkyl effect might boost C(sp)-H activation
by preventing the coordination of active iridium species to the C(sp)C(sp)
bond of enynes. This finding contributes to the fundamental understanding
of enyne cyclization reactions and offers valuable insight into the
propargylic dialkyl effect.