Sodium Thiosulfate → Tert-butyl 1-oxa-5-azaspiro[2.3]hexane-5-carboxylate

Participants

Reaction Steps

To a 0° C. solution of tert-butyl 3-methyleneazetidine-1-carboxylate (3.50 g, 20.7 mmol) in 115 ml, CHCl3 was added 77% mCPBA (13.9 g, 62.0 mmol) in 3 batches. Isopropyl alcohol (2 mL) was added. The reaction mixture was stirred for 10 minutes, then warmed to ambient temperature and stirred. After 19 hours, the milky reaction mixture was cooled to 0° C., 10 mL isopropyl alcohol was added (reaction mixture clarified), and another 1 equivalent of mCPBA was added. The reaction mixture was warmed to ambient temperature and stirred 2 hours, then another 1 equivalent mCPBA was added portionwise. After a total of 40 hours, the reaction mixture was cooled to 0° C., and 200 mL of 1:1 saturated Na2S2O3/saturated NaHCO3 was added slowly by pouring portionwise through ice (internal temperature was monitored; an initial 10° C. exotherm was observed). The mixture was stirred for 30 minutes, then extracted with CHCl3, and combined extracts were dried (Na2SO4), filtered, and concentrated. The crude was purified on silica gel (5-50% ethyl acetate in hexanes gradient) to give the desired product (1.0 g, 26.1% yield) as a clear colorless oil.

Provenance & Evidence