Imidazole → 8-Iodo-1,4-dioxaspiro[4.5]decane

A mixture of imidazole (111 g, 1.63 mol, 1.2 eq.), PPh3 (428 g, 1.63 mol, 1.2 eq.) and 1,4-dioxaspiro[4.5]decan-8-ol (215 g, 1.36 mol, 1.0 eq.) in THF (1.5 L) was cooled using an ice bath under N2. To this reaction mixture was added slowly a solution of I2 (414 g, 1.63 mol, 1.2 eq.) in THF (1 L) keeping the internal temperature <12° C. After the addition was complete, the reaction mixture was allowed to warm to room temperature and stirred overnight. The reaction mixture was partitioned between H2O (2 L), EtOAc (3 L), and brine (2 L). The aqueous layer was extracted with EtOAc (1 L×2). The combined organic layer was washed with 10% aqueous NaHSO3 (800 mL, organic layer turned light yellow), brine (1 L), dried over Na2SO4, filtered, and evaporated. The crude product was dissolved in diethyl ether (6 L), filtered, and the solid was washed with diethyl ether (300 mL×3). The filtrate was concentrated and purified by column chromatography (100% hexanes to 5% EtOAc in hexanes, Rf=0.3 in 5% EtOAc in hexanes) to give 340 g (93.4% yield) of 8-iodo-1,4-dioxaspiro[4.5]decane. GC-MS: 269 (M+1).