SYNTHESIS OF METHYL 11-IODOUNDECANOATE

• A dry 500-ml flask equipped with a septum inlet, magnetic stirrer and gas connecting tube is flushed with dry nitrogen and maintained under static pressure until work-up. 

• The flask is charged with tetrahydrofuran (100 ml) and methyl undec-10-enoate (33.7 ml, 150mmol) and cooled to °C in an ice bath. 

• Conversion to the trialkylborane is achieved by the dropwise addition of neat borane-methyl sulphide (5.10ml) over 40 minutes. 

• The ice bath is removed and the reaction allowed to stir over 1 hour at room temperature. 

• Then absolute methanol is added to destroy traces of residual hydride. 

• Iodine (38.1 g, 150mmol) is added all at once, followed by the dropwise addition of a solution of sodium methoxide in methanol (31.8 ml of a 4.72 m solution, 150mmol) over a period of 10 minutes. 

• The reaction mixture is allowed to stir for 24 hours. 

• Gas-liquid chromatography analysis (10% Dow Corning on Chromosorb W, 1.8 m x 6.3 mm) of the reaction mixture using decane for an internal standard indicates an 80 per cent yield of methyl 11-iodoundecanoate. 

• A saturated aqueous sodium thiosulphate solution is poured into the reaction mixture until excess iodine is decolourised. 

• The reaction mixture is extracted with pentane (100 ml) and dried over magnesium sulphate. Distillation under vacuum gives methyl 11-iodoundecanoate; yield 33.1 g (68%), b.p. 139-141 °C/0.15mmHg, n£° 1.4856.