Hydrochloric Acid → (-)-4,4-Diphenylperhydrothiopyrano[2,3-c]pyrrole 1-oxide

Participants

Reaction Steps

3.98 g of 4,4-diphenyl-6-tert-butyloxycarbonylbutyloxycarbonylperhydrothiopyrano[2,3-c]pyrrole 1-oxide (mixture of the 1RS,4aSR,7aSR and 1RS,4aRS,7aRS isomers) are treated with 40 cm3 of a mixture of concentrated hydrochloric acid (37% hydrochloric acid) and dioxane (1/2 by volume) for 48 hours at 20° C. The solution is concentrated to dryness at 40° C. under reduced pressure (2.7 kPa). The oil obtained is taken up in 30 cm3 of dichloromethane, the solution is washed with 60 cm3 of a 2N aqueous solution of sodium hydroxide, the aqueous phase is extracted with 20 cm3 of dichloromethane. The organic extracts are pooled, dried over magnesium sulphate and concentrated to dryness at 40° C. under reduced pressure (2.7 kPa). The residue is taken up in diisopropyl oxide and then concentrated to dryness at 40° C. under reduced pressure (2.7 and then 0.13 kPa). 3.0 g of (1RS,4aRS,7aRS)-4,4-diphenylperhydrothiopyrano[2,3-c]pyrrole 1-oxide are obtained in the form of a white meringue.

Provenance & Evidence