Ammonium Hydroxide → (R)-tert-butyl 2-(5-methoxycarbonylthiophen-2-yl)pyrrolidine-1-carboxylate

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To a solution of N-Boc-pyrrolidine (3 mL) and (−)-sparteine (3.9 mL) in tert-butyl methyl ether (36 mL) at −78° C. was added 1.4M sec-butyl lithium in cyclohexane (12.21 mL). The solution was stirred for 3 hours and 1M zinc chloride in ether (10.2 mL) was added. The mixture was stirred for 30 minutes and warmed to ambient temperature for 30 minutes. Methyl 5-bromothiophene-2-carboxylate (3.15 g), tri-tert-butylphosphine tetrafluoroborate (249 mg) and palladium(II) acetate (153 mg) were added, and the mixture was stirred at ambient temperature overnight, treated with concentrated ammonium hydroxide (1 mL) and stirred for 30 minutes, and filtered through diatomaceous earth (Celite®). The filtrate was washed with 0.5M hydrochloric acid solution and water and concentrated. The concentrate was flash chromatographed on silica gel with ethyl acetate/hexane.

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