Cesium carbonate → Tert-butyl 1-(isopropoxycarbonyl)-4-oxo-3-o-tolylpentylcarbamate

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Reaction Steps

To a solution of 2 (181.2 g, 0.557 mol) in THF (1 L) was added TEA (84.6 g, 0.836 mol) in portions at 15-20° C. The mixture was stirred for 30 h. After the reaction was complete, the solution was concentrated to give crude 7. To a solution of 35 (82.5 g, 0.557 mol) and Cs2CO3 (91 g, 0.279 mol) in DMSO (1 L) was added slowly crude 7 in DMSO (500 mL) over 30 min at 15-20° C. The mixture was stirred for 1 h. After the reaction was complete, the mixture was partitioned with water and MTBE (5 L), and extracted with MTBE twice. The combined organic layer was dried over Na2SO4 and concentrated. The crude residual was further purified by flash chromatography on silica gel (5-10% EtOAc/PE) to give 36 (138 g, 65% yield).

Provenance & Evidence