Iodine → 2-(2-Isopropylbenzoyl)benzoic acid

Participants

Reaction Conditions

Reaction Steps

Geranyl 2-(2'-isopropylbenzoyl)benzoate (2) Magnesium (0.46 g, 19 mmol) and a crystal of iodine were placed in a dry round bottom flask which was heated to activate the magnesium. Diethyl ether was added to cover the magnesium (50mL) and several drops of 2-iodoisopropyl benzene in diethyl ether were added to start the preparation of the Grignard reagent. When the latter was underway, a solution of 2-iodoisopropyl benzene (4.18 g, 17 mnol) in diethyl ether (20 mL) was added over 20 minutes. The reaction mixture was stirred for another 15 minutes and then refluxed for 20 minutes. Phthalic anhydricie (3.11 g, 21 mmol) in toluene (50 mL) was added dropwise to the Grignard reagent at room temperature. The reaction temperature was raised to 60° C. and the diethyl ether removed by evaporation. The reaction was allowed to stir at 60° C. for 6 hours. The reaction mixture was poured on ice and 10% HCl (lOOmL) and extracted twice with diethyl ether. The organic phase was washed twice with a 10% Na2CO3 solution (200 mL). The aqueous phase was acidified with acetic acid (120 mL) and extracted twice with diethyl ether (200 mL). The organic phase was washed three times with NaHCO3 (100 mL) and then twice with water. The ether phase was dried over Na2SO4, filtered and concentrated. The yield was 1.43 g (purity: 94.6%, isolated yield: 31%) of 2-(2isopropylbenzoyl)benzoic acid. For esterification, a solution of the thus obtained acid (3.77 g, 10 mmol), geraniol (1.4 g, 9 mmol) and 4-dimethylaminopyridine (DMAP, 0.244 g, 2 mmol) in pyridine (15 mL) was prepared under anhydrous conditions. 1,3-Dicyclohexylcarbodiimide (DCC, 2.06 g, 10 mmol) was added and the reaction was stirred under a stream of nitrogen gas for 52 hours. The reaction mixture was partitioned between IM HCl and ethyl acetate. The organic extract was dried over Na2SO4, filtered and concentrated under vacuum. The ester product was purified by flash column chromatography (SiO2, 7:1 cyclohexane:ethyl acetate; isolated yield: 0.7 g, 48%) to give the following analytical data:

Provenance & Evidence