Methyl chloroformate → 2,2-dimethyl-1-benzothiophen-3(2H)-one 1,1-dioxide

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Reaction Steps

To a solution of (propane-2-sulfonyl)-benzene (CAS#4238-09-9), which can be prepared as described in Cram, D. J. et al. Journal of the American Chemical Society, 1967, 89, 2072-2077, (1.18 g, 6.4 mmol) in THF (60 mL) at 0° C. is added a 2.5 M solution of n-butyl lithium in hexanes (5.8 mL, 14.7 mmol). The reaction is slowly warmed to room temperature over an hour, at which time it is re-cooled to −78° C. and methylchloroformate (0.74 mL, 9.6 mmol) is added. The reaction is brought to room temperature and permitted to stir for 16 hours. The reaction is then quenched with saturated aqueous NH4Cl and diluted with ethyl acetate. The layers are separated and the aqueous layer is extracted twice with ethyl acetate. The organic layers are combined, dried with Na2SO4, filtered, and concentrated. The resulting residue is purified by silica gel flash chromatography (ethyl acetate-heptane, 0:1 to 1:4) to provide 2,2-dimethyl-1,1-dioxo-1,2-dihydro-1lambda*6*-benzo[b]thiophen-3-one. 1H NMR (400 MHz, CDCl3) δ ppm 1.63 (s, 6 H), 7.79-7.86 (m, 1 H), 7.92-7.99 (m, 1 H), 8.03 (d, J=8.1 Hz, 2 H).

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