Lu and Shi
TMS) δ 14.1, 21.0, 24.8, 28.2, 28.6, 60.8, 78.3, 82.3, 126.7, 127.6,
127.8, 128.1, 128.9, 129.8, 129.9, 135.1, 135.8, 1402, 142.6, 143.0,
172.4; IR (CH2Cl2) ν 3056, 2979, 2906, 1738, 1492, 1444, 1362,
1277, 1189, 1170, 1132, 1032, 771, 748, 701 cm-1; MS m/z 376
(12), 303 (100), 105 (50), 275 (37), 229 (22.3), 77 (21.6), 215
(19.6), 167 (19.5), 233 (18); HRMS (EI) calcd for C25H28O3
376.2038, found 376.2072.
nature and steric effect of 8. Efforts are in progress to elucidate
further mechanistic details of these reactions and to understand
their scope and limitations.
Experimental Section
General Procedure for Lewis Acid Catalyzed Reaction of
Vinylidenecyclopropanes 1 with Ethyl Glyoxylate 8a. Under an
argon atmosphere, vinylidenecyclopropane 1 (0.2 mmol), ethyl
glyoxylate 8a (0.3 mmol), and DCE (2.0 mL) were added into a
Schlenk tube, and then BF3·OEt2 (10 mol %) was added. The
reaction mixture was stirred at 60 °C for 1.0 h, and then the solvent
was removed under reduced pressure and the residue was purified
by a flash column chromatography.
1
Compound 10a: colorless liquid; H NMR (CDCl3, 300 MHz,
TMS) δ 1.25 (t, J ) 6.9 Hz, 6H, 2CH3), 1.31 (s, 3H, CH3), 1.46
(s, 6H, 2CH3), 2.43 (s, 2H), 4.21 (q, J ) 6.9 Hz, 4H), 6.20 (d, J )
1.2 Hz, 1H), 7.15-7.17 (m, 2H, Ar), 7.23-7.31 (m, 8H, Ar); 13C
NMR (CDCl3, 75 MHz, TMS) δ 13.9, 21.5, 29.0, 33.9, 61.7, 77.6,
78.2, 124.9, 125.0, 127.0, 127.4, 127.97, 128.02, 128.2, 129.7,
133.2, 140.5, 143.9, 145.1, 169.5; IR (CH2Cl2) ν 2980, 2933, 1767,
1743, 1493, 1465, 1444, 1367, 1277, 1216, 1180, 1158, 1113, 1078,
1061, 1024, 774, 699 cm-1; MS (MALDI) m/z 449 (M+ + 1);
HRMS (MALDI) calcd for C28H32O5Na 471.2142, found 471.2150.
General Procedure for Lewis Acid Catalyzed Reaction of
Vinylidenecyclopropanes 1 with Diethyl Ketomalonate 8b. Under
an argon atmosphere, vinylidenecyclopropane 1 (0.3 mmol), diethyl
ketomalonate 8b (0.9 mmol), Nd(OTf)3 (10 mol %), and hexane
(3.0 mL) were added into a Schlenk tube. The reaction mixture
was stirred at 60 °C for 4.0 h, and then the solvent was removed
under reduced pressure and the residue was purified by flash column
chromatography.
Acknowledgment. We thank the Shanghai Municipal Com-
mittee of Science and Technology (04JC14083, 06XD14005)
and the National Natural Science Foundation of China for
financial support (20472096, 203900502, 20672127, and
20732008).
Compound 9a: colorless oil; 1H NMR (CDCl3, 300 MHz, TMS)
δ 1.10 (s, 3H, CH3), 1.28 (t, J ) 7.2 Hz, 3H), 1.58 (s, 3H, CH3),
1.60 (s, 3H, CH3), 1.62 (s, 3H, CH3), 4.18 (q, J ) 7.2 Hz, 2H),
4.50 (s, 1H), 7.15-7.28 (m, 10H, Ar); 13C NMR (CDCl3, 75 MHz,
Supporting Information Available: Spectroscopic data of all
new compounds, detailed descriptions of experimental procedures,
and X-ray data for compound 12. This material is available free of
(7) (a) Yang, D.; Yang, M.; Zhou, N.-Y. Org. Lett. 2003, 5, 3749-
3752. (b) Evans, D. A.; Tregay, S. W.; Burgey, C. S.; Paras, N. A.;
Vojkovsky, T. J. Am. Chem. Soc. 2000, 122, 7936-7943.
JO702518U
2210 J. Org. Chem., Vol. 73, No. 6, 2008