Formaldehyde → Ethyl 4-(3,4,5-trimethylpiperazin-1-yl)benzoate

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Titanium(IV) isopropoxide (0.598 mL, 2.00 mmol) was added to ethyl 4-(3,5-dimethylpiperazin-1-yl)benzoate (0.262 g, 1 mmol), and paraformaldehyde (0.120 g, 4.00 mmol) in ethanol (5 mL). The resulting solution was stirred at 60° C. under nitrogen for 30 mins. This was cooled to 20° C. and sodium borohydride (0.095 g, 2.5 mmol) was added in one portion. The solution was heated at 60° C. for 24 h. The reaction mixture was quenched with 0.880 ammonia (0.5 mL), filtered, washed with diethyl ether (2×5 mL) and the organic extracts were evaporated. The crude product was purified by silica column chromatography, eluting with a gradient of 0-5% MeOH in DCM containing 0.1% ammonia. Fractions were evaporated to dryness to afford an oil. This was dissolved in acetonitrile (20 ml), polymer supported isocyante resin (1 mmol/g, 2 g) was added and the suspension was stirred overnight. The resin was filtered off and the solution evaporated to dryness to give ethyl 4-(3,4,5-trimethylpiperazin-1-yl)benzoate (0.310 g, 112%) as a white solid. MS: m/z 278 (MH+).

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