LETTER
Stereoselective Synthesis of Pyrrolo[1,2-a]indoles
1291
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OH
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N
O
Ar
P
O
O
15 Ar = Ph
16 Ar = 4-MeC6H4
17 Ar = 4-MeOC6H4 δ(P): 16.0
18 Ar = 4-ClC6H4
δ(P): 15.7
δ(P): 15.9
δ(P): 15.9
Figure 4
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allenes with 3-chloro-2-formylindole is: allenylphospho-
nates (~4 h under heating) < allenyl sulfones (~2 h under
heating) < ester allene (~30 min under heating). In the
case of a-aryl substituted allenes 1a–f and 3a, the b,g-
product is the major or exclusive product, whereas in the
case of a-methyl substituted allenes 1g and 3b, b,a-attack
is favored. Ester allene 2 gave the b,g-product, although
this allene does not have a-substitution.
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Supporting Information for this article is available online at
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Acknowledgment
We thank the Department of Science & Technology (DST, New
Delhi) for financial support, and for use of the Single Crystal X-ray
diffractometer. M.P.P. thanks the Council of Scientific & Industrial
Research (CSIR) for a fellowship. K.C.K.S. thanks DST for a J. C.
Bose Fellowship.
Chakravarty, M.; Bhuvan Kumar, N. N.; Kumara Swamy,
K. C. J. Org. Chem. 2011, 76, 920.
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Synlett 2011, No. 9, 1288–1292 © Thieme Stuttgart · New York