[CH3:1][O:2][C:3](=[O:13])[C:4]1[CH:9]=[C:8]([Cl:10])[CH:7]=[C:6]([CH3:11])[C:5]=1[OH:12].C([O-])([O-])=O.[K+].[K+].Br[CH:21]1[CH2:24][CH2:23][CH2:22]1>CN(C)C=O>[CH3:1][O:2][C:3](=[O:13])[C:4]1[CH:9]=[C:8]([Cl:10])[CH:7]=[C:6]([CH3:11])[C:5]=1[O:12][CH:21]1[CH2:24][CH2:23][CH2:22]1A 100 mL round bottom flask is charged with 5-chloro-2-hydroxy-3-methyl-benzoic acid methyl ester (0.92 g, 4.59 mmol). Dry N,N-dimethylformamide (DMF, 15 mL) and a stirring bar are added. Stirring is initiated. After dissolution, K2SO4 (1.90 g, 13.76 mmol) and bromocyclobutane (0.65 mL, 6.88 mmol) are added. After 12 days, tlc analysis (silica, 25% EtOAc/heptanes) indicated a slight consumption of starting material and the appearance of a UV positive spot with a slightly higher Rf value. The reaction is fitted with a heating mantle and warmed to 37° C. After 3 more days, tlc analysis (silica, 25% EtOAc/heptanes) indicates a slight consumption of starting material and complete conversion to a UV positive spot with a slightly higher Rf value. The reaction mixture is filtered through a pad of Celite. The filtrate is diluted with EtOAc and (100 mL) and transferred to a separatory funnel. The EtOAc solution is washed with saturated NaHCO3 (2×25 mL) and brine (25 mL), dried over MgSO4, filtered and evaporated by pumping to constant weight to give 0.79 g of semi-solid material.
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