10.1002/chem.201901860
Chemistry - A European Journal
COMMUNICATION
carbocyclization, 4a was recovered in 65% yield, while 2-
alkynylarylketone 1a and indanone 2a were obtained in yields of
10% and 12% respectively. Without CsOAc, 4a was recovered in
82% yield, and 1a was obtained in 7% yield, while there was no
2a formed, it is because there is no CsOAc to form reactive
Cp*Rh(OAc)2 from [Cp*RhCl2]2. These results suggest that two
pathways are involved in the construction of 2a from 1a and
enolate formation of 1a is only an intermediate of the minor
pathway. Then 4a was treated under standard conditions for the
copper(I)-catalyzed 6-endo-dig carbocyclization. After 2h, 4a was
recovered in 80% yield, 9% 1a was isolated. When the reaction
was performed under 12h, the starting material partially
decomposed, as only 17% of 4a was recovered, leading to the
formation of 25% 1a. Without CsOAc, 4a was recovered in 9%
yield, while 1a and TBS-protected naphthol 6a were obtained in
the yields of 11% and 72% respectively. These results indicate
that enolate formation of 1a is the key intermediate in the
construction of 3a from 1a.
produce alkenylrhodium(III) intermediate B (from path A), gives
product
2a.
For
the
copper(I)-catalyzed
6-endo-dig
carbocyclization, the coordination of CuI to the triple bond in
intermediate D gives intermediate F (path D). Subsequent
intramolecular 6-endo-dig carbocyclization produces intermediate
G, which undergoes protonation by acetic acid to produce 3a.
In summary, we have developed a catalyst-controlled
intramolecular carbocyclization of 2-alkynylarylketones. Under
rhodium(III)-catalyzed 5-exo-dig carbocyclization, 1-indanones
are obtained in an exclusive chemo-, regio- and stereoselective
manner. When employing copper(I)-catalyzed 6-endo-dig
carbocyclization, 1-naphthols are chemo- and regioselectively
produced.
Acknowledgements
Liangliang Song and Guilong Tian appreciate the China
Scholarship Council (CSC) for providing a doctoral scholarship.
We acknowledge the FWO [Fund for Scientific Research-
Flanders (Belgium)] for financial support. We acknowledge the
support of RUDN University Program 5-100.
Keywords: carbocyclization • C-H activation • rhodium • copper
• enolate
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