2-bromo-7-iodo-3-(trifluoromethoxy)-9H-xanthen-9-one → 2-bromo-7-iodo-9-methyl-3-(trifluoromethoxy)-9H-xanthen-9-ol

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A RBF was charged with 2-bromo-7-iodo-3-(trifluoromethoxy)-9H-xanthen-9-one (2.94 g, 6.06 mmol) and THF (33.7 mL). The black suspension was cooled to −78° C. using an i-PrOH/dry ice bath. Methylmagnesium chloride (3.0 M in THF, 4.45 mL, 13.34 mmol) was added dropwise. After 2 h, LCMS showed olefin product. The whole was quenched with satd' aq NH4Cl (20 mL) at 0° C., water (50 mL) and diluted with EtOAc (100 mL). The product was extracted with EtOAc (3×50 mL). The organic layer was separated, dried over MgSO4, filtered, and concentrated to afford yellow oil. 1H NMR confirmed the tertiary alcohol, 2-bromo-7-iodo-9-methyl-3-(trifluoromethoxy)-9H-xanthen-9-ol (3.04 g, 6.07 mmol, 100% yield). LCMS (ESI) calcd for C15H9BrF3IO3: [M]+=500. Found [M−H2O+H]+=483. Dehydration took place on LCMS to give the olefin, 2-bromo-7-iodo-9-methylene-3-(trifluoromethoxy)-9H-xanthene). This material was carried on to the next step.

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