Compound 18

3-chloro-1-methylcyclohex-1-ene

From: Simplified immunosuppressive and neuroprotective agents based on gracilin A

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Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

N-chlorosuccinimide (2.48 g, 18.6 mmol, 1.10 equiv) was weighed into an oven-dried, round-bottomed flask and suspended in CH2Cl2 (33.0 mL). The slurry was cooled to 0 ºC and Me2S (1.61 mL, 21.9 mmol, 1.30 equiv) was added dropwise over ~5 min producing a white solution. 3-Methylcyclohex-2-en-1-ol (2.00 mL, 16.8 mmol, 1.00 equiv) was added dropwise with vigorous stirring to provide a clear solution. Within ~10 min, a precipitate formed. The reaction was continued at 0 ºC for 2 h and concentrated under reduced pressure. Pentane (50 mL) was added leading to immediate formation a white precipitate. The flask was then placed in a freezer for 4 h and the supernatant was decanted. The remaining solid was washed with cold pentane (2 x 50 mL) and the combined organics were washed with brine (2 x 50 mL), dried over MgSO4, and concentrated in vacuo. Allyl chloride 18 was isolated as a clear colorless oil, (1.76 g, 80%) and this material was of sufficient purity (>95% as judged by 1H-NMR) to be carried directly to the next step without purification. TLC (EtOAc/hexanes, 3:7 v/v), Rf = 0.79. Spectral data matched that previously reported (Ren, H., Dunet, G., Mayer, P. and Knochel, P. J. Am. Chem. Soc., 2007, 129, 5376-5377).