ChemComm
Communication
In conclusion, the competitive occurrence of C–H insertion
of platinum isochromenyliums over an alkyl shift has been
highlighted. Enynones 1a–s underwent Huisgen-type cyclo-
addition with an alkene to give the tetracyclic platinum–
carbene complex B, which could form both tetrahydrofuran
and tetrahydropyran via C–H insertion at d or e positions to give
highly complex O-bridged polycycles, which are otherwise hard
to access.
Fig. 2 X-ray structures of 2a and 2b.
Financial support was provided by a grant from the National
Research Foundation of Korea (NRF 3 201200000000953).
eventually preventing the formation of products as a result of alkyl
migration. Although 1o furnished the expected 2o as a mixture of
diastereomers (a:b = 1 :2) in 62% yield, 2p still afforded a 1 : 1
mixture of pre-3p and 3p in 79% yield. Due to the substituent
effect in the p-methoxy derivative (1p) of 1o, its reaction would
proceed via an intermediate E to afford pre-3p selectively and then
its rearranged product 3p. The isolation of pre-3p in addition to
3p approved the mechanistic interpretation.
Three more homologs 1q–s, different from 1a in the chain
length, were examined for the competitive occurrence of intra- and
inter-molecular cycloaddition. While 1r underwent intramolecular
cycloaddition, followed by alkyl shift to give 3r exclusively, neither
1q nor 1s could afford either type-2 or type-3 product (Scheme 3).
The reason for selectivity might be the fact that 1r (n = 3) has
to form a stable 6-membered intermediate to afford thermo-
dynamically stable 3r in 74% yield whereas 1q and 1s would
require the formation of more strained 4- and 7-membered inter-
mediates. However both 1q and 1s underwent intermolecular
cycloaddition with N-ethylmaleic imide (5) following C–H insertion
to afford 2q and 2s, respectively. 2q and 2s were each obtained as a
single diastereomer. The finding that 1q and 1s formed the
isochromenylium intermediates and further underwent inter-
molecular cycloadditions with an external dipolarophile 5 to give
the corresponding 2q and 2s, while 1r preferred intramolecular
cycloaddition, is valuable.
Notes and references
1 (a) G. Illuminati and L. Mandoline, Acc. Chem. Res., 1981, 14, 95;
(b) G. A. Molander, Acc. Chem. Res., 1998, 31, 603.
2 (a) M. B. Fraga, Nat. Prod. Rep., 2005, 22, 465; (b) D. G. I. Kingston,
H. Yuan, P. G. Jagtap and L. Samala, in The Chemistry of Organic
Natural Products, ed. W. Herz, G. W. Kirby, R. E. Moore, W. Steglich
and C. Tamm, Springer, New York, 2002, vol. 84.
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3 (a) B. Trillo, F. Lopez, M. Gulıas, L. Castedo and J. L. Mascarenas,
Angew. Chem., Int. Ed., 2008, 47, 951; (b) M. A. Battiste,
P. M. Pelphrey and D. L. Wright, Chem.–Eur. J., 2006, 12, 3438;
(c) P. A. Wender, F. C. Bi, N. Buschmann, F. Gosselin, C. Kan,
J.-M. Kee and H. Ohmura, Org. Lett., 2006, 8, 5373; (d) B. M. Trost,
Y. Hu and D. B. Horne, J. Am. Chem. Soc., 2007, 129, 11781.
4 (a) C. H. Oh, H. J. Yi, J. H. Lee and D. H. Lim, Chem. Commun., 2010,
46, 3007; (b) A. K. Gupta, C. Y. Rhim, C. H. Oh, R. S. Maneb and
S.–H. Han, Green Chem., 2006, 8, 25.
5 (a) R. Huisgen, Angew. Chem., Int. Ed., 1968, 7, 321; (b) H. Hamberger
and R. Huisgen, J. Chem. Soc. D, 1971, 1190; (c) K. Saito, H. Sogou,
T. Suga, H. Kusama and N. Iwasawa, J. Am. Chem. Soc., 2011,
133, 689.
6 (a) S. Shin, A. K. Gupta, C. Y. Rhim and C. H. Oh, Chem. Commun.,
2005, 4429; (b) N. Kim, Y. Kim, W. Park, D. Sung, A. K. Gupta and
C. H. Oh, Org. Lett., 2005, 7, 5289; (c) C. H. Oh, J. H. Ryu
and H. I. Lee, Synlett, 2007, 2337; (d) C. H. Oh, S. J. Lee, J. H. Lee
and Y. J. Na, Chem. Commun., 2008, 5794; (e) C. H. Oh, S. M. Lee and
C. S. Hong, Org. Lett., 2010, 12, 1308; ( f ) C. H. Oh, J. H. Lee, S. J. Lee,
J. I. Kim and C. S. Hong, Angew. Chem., Int. Ed., 2008, 47, 7505;
(g) C. H. Oh, J. H. Lee, S. M. Lee, H. J. Yi and C. S. Hong, Chem.–Eur. J.,
2009, 15, 71.
7 (a) H. Kusama, K. Ishida, H. Funami and N. Iwasawa, Angew. Chem.,
Int. Ed., 2008, 47, 4903; (b) K. Ishida, H. Kusama and N. Iwasawa,
J. Am. Chem. Soc., 2010, 132, 8842.
8 N. Asao, K. Sato, Menggenbateer and Y. Yamamoto, J. Org. Chem,
2005, 70, 3682.
9 (a) M. Kawano, T. Kiuchi, S. Negishi, H. Tanaka, T. Hoshikawa,
J. Matsuo and H. Ishibashi, Angew. Chem., Int. Ed., 2013, 52, 906;
(b) M. E. Hayes, H. Shinokubo and R. L. Danheiser, Org. Lett., 2005,
7, 3917; (c) L. Jiao, M. Lin and Z.–X. Yu, Chem. Commun., 2010,
46, 1059; (d) Q. Cai and S.-L. You, Org. Lett., 2012, 14, 3040;
(e) H. Horie, T. Kurahashi and S. Matsubara, Chem. Commun.,
2012, 48, 3866; ( f ) K. M. Wiggins, J. A. Syrett, D. M. Haddleton
and C. W. Bielawski, J. Am. Chem. Soc., 2011, 133, 7180;
(g) N. Iwasawa, I. Ooi, K. Inaba and J. Takaya, Angew. Chem., Int.
Ed., 2010, 49, 7534.
10 (a) H. Kusama, H. Funami, M. Shido, Y. Hara, J. Takaya and
N. Iwasawa, J. Am. Chem. Soc., 2005, 127, 2709; (b) N. Iwasawa,
M. Shido and H. Kusama, J. Am. Chem. Soc., 2001, 123, 5814;
(c) K. Miki, T. Yokoi, F. Nishino, Y. Kato, Y. Washitake, K. Ohe
and S. Uemura, J. Org. Chem., 2004, 69, 1557; (d) Y. Horino,
T. Yamamoto, K. Ueda, S. Kuroda and F. D. Toste, J. Am. Chem.
Soc., 2009, 131, 2809; (e) D. Shikanai, H. Murase, T. Hata and
H. Urabe, J. Am. Chem. Soc., 2009, 131, 3166.
Scheme 2 Possible mechanism for the formation of 2o and 3p.
11 The identity of all the products was confirmed by FT-IR, 1H NMR,
13C NMR spectroscopy and HRMS.
12 (a) H. Kusama, Y. Karibe, Y. Onizawa and N. Iwasawa, Angew. Chem.,
Int. Ed., 2010, 49, 4269; (b) X.-Z. Shu, X.-Y. Liu, K.-G. Ji, H.-Q. Xiao
and Y.-M. Liang, Chem.–Eur. J., 2008, 14, 5282; (c) Y.-F. Yang,
X.-Z. Shu, J.-Y. Luo, S. Ali and Y.-M. Liang, Chem.–Eur. J., 2012,
18, 8600.
Scheme 3 Intramolecular vs. intermolecular cyclization of enynones.
5692 Chem. Commun., 2013, 49, 5690--5692
13 CCDC 921219 and 921220†.
c
This journal is The Royal Society of Chemistry 2013