Hydrochloric Acid → (S)-tert-butyl 1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-1-oxopropan-2-ylcarbamate

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A suspension of (S)-tert-butyl 1-(methoxy(methyl)amino)-1-oxopropan-2-ylcarbamate (3 g, 12.92 mmol) in THF (30 mL) was placed under a protective atmosphere of Argon and cooled down to −15 to −20° C., isopropylmagnesium chloride, 2M in THF (6.5 mL, 13.00 mmol) was added keeping the temperature below −10° C. The slurry started to dissolve, temperature was allowed to reach 0° C., a freshly prepared solution of (2,3-dihydrobenzo[b][1,4]dioxin-6-yl)magnesium bromide, 0.7M in THF (20 mL, 14.00 mmol) was added. The temperature was allowed to reach r.t., the reaction mixture was stirred for 17 h. 1N HCl (300 mL) was cooled on icebath to +10° C., the reaction mixture was poured into the acidic water solution, TBME=tert-butyl methyl ether (300 mL) was added and the mixture was transferred to a separation funnel. The waterphase was backextracted with TBME (200 mL). The ether phases were washed with water, brine and dried (Na2SO4).

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