Rutheniun-catalyzed cycloisomerization of o-(ethynyl)phenylalkenes to diene derivatives via skeletal rearrangement.
Treatment of a series of 2',2'-disubstituted (o-ethynyl)styrenes with TpRu(PPh(3))(CH(3)CN)(2)PF(6) (10 mol %) in benzene (80 degrees C, 12-18 h) efficiently gave 2-alkenyl-1H-indene derivatives. This catalytic reaction represents an atypical enyne cycloisomerization with skeletal rearrangement of starting enyne, where the C=C bond is completely cleaved and inserted by the terminal alkynyl carbon. The reaction mechanism was elucidated by a series of deuterium and (13)C labeling experiments, as well as by changing the substituents at the phenyl moieties. The mechanism is proposed to involve the following key steps: 5-endo-dig cyclization of ruthenium-vinylidene intermediate, a nonclassical ion formation, and the "methylenecyclopropane-trimethylenemethane" rearrangement.
Madhushaw
Reniguntala J
RJ
Department of Chemistry, National Tsing-Hua University, Hsinchu 30043, Taiwan, Republic of China.
Lo
Ching-Yu
CY
Hwang
Chun-Wei
CW
Su
Ming-Der
MD
Shen
Hung-Chin
HC
Pal
Sitaram
S
Shaikh
Isak R
IR
Liu
Rai-Shung
RS