2,3,3a,6a-tetrahydrofuro[2,3-b]furan-4-one

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:-5.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Hexahydrofuro[2,3-b]furan-3-ol (55 g) was dissolved in dichloromethane (385 ml) sodium bicarbonate (10%, 165 ml) was added to it and cooled to −5° C. Potassium bromide (2.0 g), 2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) (1.0 g) and Tetrabutyl ammonium bromide (1.0 g) was charged to the reaction. Sodium hypochlorite solution (365 ml) was added slowly by maintaining temp 0 to −6° C. Reaction mass was then maintained at 0 to −6° C. for 1 hr. Aqueous layer was separated and extracted with dichloromethane (2×110 ml) combined dichloromethane layers was washed with hydrochloride solution (10%, 110 ml) and Sodium thiosulphate solution (10%, 110 ml). Dichloromethane was then concentrated to residue, the residue was dissolved in isopropyl alcohol (40 ml) & methyl tert-butyl ether (40 ml) and cooled to 0-5° C., and filtered the solid to get the pure solid material of Tetrahydrofuro[2,3-b]furan-3(2H)-one (39 g) having purity 99.18%. was added to it by maintaining temp 0 to −6° C Reaction mass was then maintained at 0 to −6° C. for 1 hr Aqueous layer was separated extracted with dichloromethane (2×110 ml) was washed with hydrochloride solution (10%, 110 ml) and Sodium thiosulphate solution (10%, 110 ml) Dichloromethane was then concentrated to residue the residue was dissolved in isopropyl alcohol (40 ml) methyl tert-butyl ether (40 ml) and cooled to 0-5° C. filtered the solid

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Generally in accordance with the procedure described by Ghosh et al in J. Org. Chem. 2004, 69, 7822-7829, tetrahydrofuro[2,3-b]furan-3(2H)-one (950 mg, 7.42 mmol, 1 eq.) was dissolved at 0° C. in 50 mL of ethanol. NaBH4 (302.4 mg, 8 mmol, 1.07 eq.) was added in one portion to the mixture. After a 1 hour stirring period, diethanolamine hydrochloride salt (3.2 g, 8 mmol, 1.07 eq.) was added and the mixture was stirred overnight at room temperature. The heterogeneous mixture was filtered over dicalite and washed with 20 mL of warm AcOEt. After evaporation of the organic solvents under reduced pressure to afford 1500 mg of hexahydrofuro[2,3-b]furan-3-ol with a quality (area %) of 40%; max yield: 60%. diastereoisomeric excess: exo(3S,3aS,6aR)/endo (3R,3aS,6aR): 18.5/81.5. the mixture was stirred overnight at room temperature The heterogeneous mixture was filtered over dicalite washed with 20 mL of warm AcOEt After evaporation of the organic solvents under reduced pressure

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In a 250 mL round bottom flask, NaOCl (6.15 g, 14% w/w) was diluted in 100 mL of water. The pH of the solution was adjusted to 9.5 using a 1M NaHCO3 aqueous solution. In a separate 250 mL round bottom flask, hexahydrofuro[2,3-b]furan-3-ol (1 g, 7.7 mmol, 1 eq.) was dissolved in 15 mL of AcOEt at 0° C. Then KBr (91 mg, 0.77 mmol, 0.1 eq.) dissolved in 1 mL of water was added followed by the addition of TEMPO (12 mg, 0.08 mmol, 0.01 eq.). Finally, the NaOCl mixture was added dropwise. After 15 minutes of stirring at 0° C., the mixture was extracted 3 times with 100 mL of AcOEt. The collected organic layers were dried over Na2SO4 and the solvent was evaporated under reduced pressure to afford 950 mg of a white solid, yield: 96%. The resulting tetrahydrofuro[2,3-b]furan-3(2H)-one was used in the next step without further purification. was added the mixture was extracted 3 times with 100 mL of AcOEt The collected organic layers were dried over Na2SO4 the solvent was evaporated under reduced pressure