Hydrochloric Acid → 2,3-dihydrospiro[4H-1-benzothiopyran-4,2'-[1,3]dioxolane]-6-carboxylic acid 1,1-dioxide

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Reaction Conditions

Reaction Steps

8.5 g (0.034 mol) of the title compound of Step D and 41.5 g (0.51 mol) of sodium acetate were added to 160 mL of methanol. The suspension was cooled to about 0° C., and a solution of 35.2 g (0.057 mol) of OXONE® (potassium peroxymonosulfate, purchased from Aldrich Chemical Company) in 160 mL of water was added dropwise while keeping the temperature below 6° C. The mixture was warmed to room temperature and stirred under nitrogen overnight. The mixture was diluted with 100 mL of water, cooled to about 0° C., acidified to pH 2 with concentrated hydrochloric acid, and extracted with chloroform (3×200 mL). The combined organic layers were dried (MgSO4), filtered, and evaporated to dryness. The crude product was triturated with a hexane:diethyl ether mixture (9:1) to yield 6.98 g of the title compound of Step E as a solid melting at 208° C. (dec). 1H NMR (Me2SO-d6): δ2.6 (m,2H), 3.7 (m,2H), 4.1-4.2 (m,4H), 7.9-8.15 (3H), 13.6 (br s,1H).

Provenance & Evidence