[Cl-].[Mg+2].[Cl-].[OH:4][C:5]1[CH:10]=[CH:9][CH:8]=[C:7]([CH2:11][CH3:12])[C:6]=1[OH:13].C(N(CC)CC)C.[CH2:21]=[O:22].Cl>C(#N)C.C(OCC)C>[OH:4][C:5]1[C:6]([OH:13])=[C:7]([CH2:11][CH3:12])[CH:8]=[CH:9][C:10]=1[CH:21]=[O:22]Magnesium chloride (1.71 g, 18 mmol) was added at room temperature to a solution of 10 (1 g, 7.2 mmol) in acetonitrile (10 mL), followed by triethylamine (6.3 mL, 45 mmol). Paraformaldehyde (1.47 g, 49 mmol) was then added portionwise to the stirred suspension and the mixture was heated at reflux for 2 hours. The mixture was cooled to room temperature then poured into a vigorously stirred mixture of 50 mL of 5% HCl and 50 mL of diethyl ether. The organic phase was separated, and the aqueous layer re-extracted with 50 mL of ether. The combined organic extracts were washed with brine, dried over sodium sulphate and the solvent removed under reduced pressure to give a crude which was purified by column (cyclohexane:AcOEt 6:1) to give 0.9 g of 11:
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