117.62, 133.35, 136.48, 171 .97; EIMS: m/z [280, (MH+-CH3)]; Anal. Calcd. For C17H26O4 (294.39): C, 69.36; H, 8.90; Found: C, 69.51; H, 9.49.
8-[2(2,2-Dimethyl-[1,3]dioxalan-4-yl)-cyclopropyl]-3,4,7,8-tetrahydro-oxacin-2-one (5). A solution of 6 (0.1g, 0.34 mmol) and freshly distilled Ti(Oi-Pr)4 (0.01 mL, 0.03mmol) in anhydrous CH2Cl2 (200 mL) was refluxed for 2h under an argon atmosphere. Grubbs’ “second generation” catalyst (20 mg) in dry CH2Cl2 (5 mL) was added to it. The reaction mixture was then refluxed for 48h. After completion of the reaction (monitored by TLC), the reaction mixture was filtered through a pad of silica gel. The organic solvent was removed under reduced pressure and the residue was purified by silica gel column chromatography using ethyl acetate/light petroleum ether (1:9) to afford 64mg (71%) of pure compound 5. Colorless liquid; [a]D – 4.58 (c 0.4, CHCl3), lit.3a [a]D = - 4.66 (c 0.9, CHCl3); IR(neat) 1746 cm-1; 1H NMR (200 MHz, CDCl3) d 0.63 (m, 1H), 0.71 (m, 1H), 0.96 (m, 2H), 1.31 (s, 3H), 1.40 (s, 3H), 2.25-2.44 (m, 6H), 3.61 (m, 2H), 4.02 (m, 1H), 4.40 (m, 1H), 5.10 (m, 2H); 13C NMR (50 MHz, CDCl3) d 9.45, 18.94, 19.03, 25.62, 26.72, 27.26, 33.91, 36.93, 69.05, 76.28, 78.88, 109.11, 127.64, 129.02, 172.67; EIMS : m/z [252, (MH+ - CH3)]; Anal. Calcd. For C15H22 O4 (266.34) : C, 67.65; H, 8.33; Found: C, 68.28; H, 7.83.
Acknowledgements
GSY thanks CSIR, New Delhi for award of Junior Research Fellowship. We are grateful to Dr. M. K Gurjar, Head, Organic Chemistry: Technology Division for his constant encouragement and support.
References
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