SYNTHESIS OF CYCLOOCTANE

STEP 1: An oven-dried 300-m1 flask, equipped with a side-arm fitted with a silicone rubber septum, a magnetic stirrer bar, and a reflux condenser connected to a mercury bubbler, is cooled to room temperature under a stream of dry nitro­gen. 

STEP 2: Tetrahydrofuran (20 ml) is introduced, followed by 7.1 g (25 mmol) of cyclooctyl tosylate (1).

STEP 3: The mixture is cooled to 0 °C (ice bath).

STEP 4: To this stirred solution, lithium triethylborohydride [33.3 ml (50 mmol) of a 1.5 M solution in tetrahydrofuran] is added, and the ice bath removed. 

STEP 5: The mixture is stirred for 2 hours (c. 25 °C). Excess hydride is decomposed with water. 

STEP 6: The organoborane is oxidised with 20 ml of 3 m sodium hydroxide solution and 20 ml of 30 per cent hydrogen peroxide [(2) and (3)]. Then the tetrahydrofuran layer is separated. 

STEP 7: The aqueous layer is extracted with 2 x 20 ml portions of pentane. 

STEP 8: The combined organic extracts are washed with 4 x 15 ml portions of water to remove ethanol produced in the oxidation. The organic extract is dried (MgSO₄) and volatile solvents removed by distillation (2). 

STEP 9: Distillation of the residue yields 2.27 g (81%) of cyclooctane as a colourless liquid, b.p. 142-146 °C, nU1.4630.

Notes to keep in mind:

1. The editors emphasise the CAUTIONARY notes relating to the handling of hydrogen peroxide, and to the distillation of extracts following the use of tetrahydrofuran/hydrogen peroxide in oxidation procedures.