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DOI: 10.1039/C7CC06276A
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intermediate as proposed in Figure 6. Both conformations
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3
conformation
I is more favourable which led to cis-geometry
as a major isomer (Figure 6). Further, we expected that dual
cyclization could also be possible if product 3a would be
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treated with excess of Cu(OAc)
2
. However, the formation of
4
5
1,
product 9 was not detected under these conditions showing
4
that the presence of an extra phenyl group is necessary to
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Figure 6. Proposed mechanism for radical cyclization.
8
,
In conclusion, a highly versatile and efficient Ru(II)-catalysed
cascade C-H functionalization/cyclization approach has been
described for the dual formation of C-C bonds resulting in an
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expedient access to pyrrolo[1,2-a]indole
3 by the utilization of
2
very simple starting materials with moderate to good yields,
sustainable substrate choice and controlled regio- and
diastereoselectivity. Moreover, the method can be expanded
to three successive C-H activations to furnish
,
,
2
indeno[2’,1’:3,4]pyrrolo[1,2-a]indole skeletons 5. The method
9
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This work was supported by the research fund of the KU
Leuven and FWO (Fund for Scientific Research–Flanders,
Belgium). SS is thankful to Erasmus Mundus Expert 2 program
for granting a post-doctoral fellowship. HB is thankful to the
Department of Chemistry, Saurashtra University, Rajkot, UGC-
BSR for granting a doctoral scholarship and to the Erasmus
Mundus Experts 2 program for providing a visiting doctoral
fellowship. DDV is thankful to KU Leuven for providing a post-
doctoral fellowship. The publication was financially supported
by The Ministry of Education and Science of the Russian
Federation (the Agreement number 02.a03.0008).
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