Ethylene Glycol → 6-Bromo-5,8-dimethylspiro[thiochromane-4,2'-[1,3]dioxolane]

Participants

Reaction Steps

26.06 g (0.096 mol) of the title compound of Step C, 250 mL of ethylene glycol, 170 mL of trimethyl orthoformate (purchased from Aldrich Chemical Company), and 0.06 g of p-toluenesulfonic acid monohydrate were stirred together at 80° C. under nitrogen overnight. The mixture was diluted with 400 mL of diethyl ether. The resulting mixture was washed with a 1:1 mixture of 1N sodium hydroxide:saturated aqueous NaCl (2×600 mL) and then with saturated aqueous NaCl (1×600 mL). The organic layer was dried (Na2SO4), filtered, and evaporated to dryness. The crude product was chromatographed over silica gel eluting with a mixture of ethyl acetate:hexane (1:9) to yield 24.73 g of the title compound of Step D as a solid melting at 97° C. (dec). 1H NMR (CDCl3): δ2.2 (s,3H), 2.3 (m,2H), 2.4 (s,3H), 3.0 (m,2H), 4.15 (m,2H), 4.3 (m,2H), 7.3 (s,1H).

Provenance & Evidence