2802
B. P. Machin, B. L. Pagenkopf
LETTER
F.; Gertsch, J.; Waser, J. Angew. Chem. Int. Ed. 2010, 49,
5767. (p) Smith, A. G.; Slade, M. C.; Johnnson, J. S. Org.
Lett. 2011, 13, 1996. (q) De Simone, F.; Waser, J. Synlett
2011, 589.
V. S.; Greenstein, M.; Janso, J. E.; Maiese, W. M.; Mayne,
C. L.; Ireland, C. M. J. Org. Chem. 2003, 68, 2014.
(d) Ankisetty, S.; ElSohly, H. N.; Li, X.-C.; Khan, S. I.;
Tekwani, B. L.; Smillie, T.; Walker, L. J. Nat. Prod. 2006,
69, 692. (e) Kim, S.; Chin, Y.-W.; Su, B.-N.; Riswani, S.;
Kardono, L. B. S.; Afriastini, J. J.; Chai, H.; Farnsworth, N.
R.; Cordell, G. A.; Swanson, S. M.; Kinghorn, A. D. J. Nat.
Prod. 2006, 69, 1769. (f) Liermann, J. C.; Kolshorn, H.;
Opatz, T.; Thines, E.; Anke, H. J. Nat. Prod. 2009, 72,
1905. (g) Bruder, M.; Haseler, P. L.; Muscarella, M.; Lewis,
M.; Moody, C. J. J. Org. Chem. 2010, 75, 353. (h) Wang,
Y.; Zheng, Z.; Liu, S.; Zhang, H.; Li, E.; Guo, L.; Che, Y.
J. Nat. Prod. 2010, 73, 920.
(3) For selected examples, see: (a) Carson, C. A.; Kerr, M. A.
Angew. Chem. Int. Ed. 2006, 45, 6560. (b) Young, I. S.;
Kerr, M. A. J. Am. Chem. Soc. 2007, 129, 1465.
(c) Kalidindi, S.; Jeong, W. B.; Schall, A.; Bandichhor, R.;
Nosse, B.; Reiser, O. Angew. Chem. Int. Ed. 2007, 46, 6361.
(d) Morales, C. L.; Pagenkopf, B. L. Org. Lett. 2008, 10,
157. (e) Leduc, A. B.; Kerr, M. A. Angew. Chem. Int. Ed.
2008, 47, 7945. (f) Bajtos, B.; Pagenkopf, B. L. Eur. J. Org.
Chem. 2009, 1072. (g) Carson, C. A.; Kerr, M. A. Org. Lett.
2009, 11, 777. (h) Karadeolian, A.; Kerr, M. A. Angew.
Chem. Int. Ed. 2010, 49, 1133. (i) Jung, M. E.; Chang, J. L.
Org. Lett. 2010, 12, 2962.
(8) Lewis acids screened included: Yb(OTf)3, Sc(OTf)3,
Zn(OTf)2, ZnBr2, MgCl2, MgBr2, InBr3, TiCl4, Cu(OTf)2,
and BiCl3 at temperatures ranging from 0 °C to refluxing and
at ambient pressure to 1103 bar in a high-pressure reactor.
(9) Representative Procedure for the Preparation of 4a
To a solution of cyclobutane 1 (105 mg, 0.43 mmol, 1 equiv)
and phenylacetylene (50 mL, 0.49 mmol, 1.1 equiv) in DCE
(6 mL, 0.1 M) was added BF3·OEt2 (55 mL, 0.43 mmol, 1
equiv). A reflux condenser was quickly attached, and the
flask was placed in a preheated oil bath. After complete
consumption of the cyclobutane as indicated by TLC (15
min), the reaction mixture was poured into a separatory
funnel containing a half-saturated solution of NaHCO3. The
aqueous phase was extracted with CH2Cl2 (3 × 5 mL), and
the combined organic extracts were washed with brine, dried
over MgSO4, filtered through a pad of Celite, and
(4) (a) Moustafa, M. M. A. R.; Pagenkopf, B. L. Org. Lett. 2010,
12, 4732. (b) Moustafa, M. M. A. R.; Stevens, A. C.;
Machin, B. P.; Pagenkopf, B. L. Org. Lett. 2010, 12, 4736.
(c) Stevens, A. C.; Palmer, C.; Pagenkopf, B. L. Org. Lett.
2011, 13, 1528.
(5) (a) Shimada, S.; Saigo, K.; Nakamura, H.; Hasegawa, M.
Chem. Lett. 1991, 20, 1149. (b) Matsuo, J.-i.; Sasaki, S.;
Tanaka, H.; Ishibashi, H. J. Am. Chem. Soc. 2008, 130,
11600. (c) Parsons, A. T.; Johnson, J. S. J. Am. Chem. Soc.
2009, 131, 14202. (d) Matsuo, J.-i.; Sasaki, S.; Hoshikawa,
T.; Ishibashi, H. Org. Lett. 2009, 11, 3822. (e) Allart, E. A.;
Christie, S. D. R.; Pritchard, G. J.; Elsegood, M. R. J. Chem.
Commun. 2009, 7339. (f) Matsuo, J.-i.; Okado, R.;
Ishibashi, H. Org. Lett. 2010, 12, 3266. (g) Negishi, S.;
Ishibashi, H.; Matsuo, J.-i. Org. Lett. 2010, 12, 4984.
(6) (a) Yadav, V. K.; Sriramurthy, V. Angew. Chem. Int. Ed.
2004, 43, 2669. (b) Qi, X.; Ready, J. M. Angew. Chem. Int.
Ed. 2008, 47, 1. (c) Matsuo, J.-i.; Negishi, S.; Ishibashi, H.
Tetrahedron Lett. 2009, 50, 5831. (d) Matsuo, J.-i.; Sasaki,
S.; Hoshikawa, T.; Ishibashi, H. Chem. Commun. 2010, 46,
934.
concentrated in vacuo. The crude reaction product was
purified by flash column chromatography (hexanes–EtOAc
= 4:1) to provide the corresponding addition–rearrangement
product 4a (79 mg, 53%) as a yellow oil. Rf = 0.49 (hexanes–
EtOAc = 4:1). 1H NMR (600 MHz, CDCl3): d = 7.56–7.55
(m, 2 H), 7.31–7.29 (m, 2 H), 7.27–7.25 (m, 1 H), 5.72 (d,
J = 8.8 Hz, 1 H), 5.53 (d, J = 8.8 Hz, 1 H), 4.32 (app t,
J = 4.1 Hz, 2 H), 4.19 (q, J = 4.0 Hz, 4 H), 3.55 (t, J = 7.9
Hz, 1 H), 2.73 (d, J = 8.2 Hz, 2 H), 2.62 (app t, J = 4.1 Hz, 2
H), 1.25 (t, J = 7.0 Hz, 6 H). 13C NMR (100 MHz, CDCl3):
d = 169.0(2), 157.4, 137.5, 137.0, 128.3 (2), 128.1, 125.3 (2),
122.1, 99.1, 69.0, 61.5 (2), 51.0, 38.8, 37.1, 14.1 (2). HRMS:
m/z calcd for C20H24O5: 344.1624; found: 344.1617.
(7) For selected examples of seven-membered oxacyclic-
containing natural products, see: (a) Rastetter, W. H.;
Chancellor, T.; Richard, T. J. J. Org. Chem. 1982, 47, 1509.
(b) Zamarano, G.; Catalán, C. A. N.; Diaz, J. G.; Herz, W.
Phytochemistry 1995, 38, 1257. (c) Bugni, T. S.; Bernan,
Synlett 2011, No. 19, 2799–2802 © Thieme Stuttgart · New York