A.
1,4-Dithiaspiro[4.11]hexadecane. A mixture of
46.5 g (0.26 mol) of cyclododecanone (Note
1),
24.1 g (21.5 mL, 0.26 mol) of 1,2-ethanedithiol (Note
1), and
0.75 g (0.004 mol) of p-toluenesulfonic acid monohydrate (Note
2), in
200 mL of toluene (Note
3) is placed in a
500-mL, three-necked reaction flask equipped for
reflux under a
water separator.
2 The mixture is heated at reflux for several hours until the theoretical amount of water (0.26 mol = 4.6 mL) has collected in the
Dean-Stark trap. The reaction mixture is cooled and transferred to a
separatory funnel. The mixture is washed with water, the
toluene is removed on a
rotary evaporator, and the residue is placed under reduced pressure (< 0.1 mm) for several hours to remove traces of solvent. Approximately
66 g (
99%) of a white solid is recovered (0.26 mol, mp 84–86°C). The crude material is pure by GLC and TLC, and is used in the next step with no further purification.
B.
Cyclododecyl mercaptan. In a
1-L, three-necked, round-bottomed flask equipped with a
mechanical stirrer and
nitrogen inlet and outlet stopcocks are placed
25.8 g (0.10 mol) of 1,4-dithiaspiro[4.11]hexadecane and
300 mL of ether, freshly distilled from
sodium. The mixture is purged with
nitrogen, cooled to 0°C with an
ice bath, and
125 mL (0.30 mol, 2.4 M in hexane) of butyllithium is added by syringe (Note
4), (Note
5) under a slow flow of
nitrogen. The light-yellow mixture is then allowed to warm to room temperature and stirred overnight with nitrogen stopcocks closed (Note
6). The reaction mixture is cooled to 0°C and 50 mL of water is added slowly and very carefully (Note
7). The resulting light brown solution is poured into 200 mL of water in a
separatory funnel and, after shaking, the organic layer is separated. The solution is dried over MgSO
4, concentrated (aspirator), and distilled through a
10-cm Vigreux column at 103–108°C (1 mm) to give
17.2–17.9 g (
86–90%) of pure
cyclododecyl mercaptan (Note
8), (Note
9). A small forerun, bp < 95°C, (ca. 2 mL) is discarded.