4-methoxy-3,6-dihydro-2H-pyran

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

Procedure: To a solution of 4-methoxy-3,6-dihydro-2H-pyran (5.00 g, 43.8 mmol) in methanol (100 mL) at 0° C. was dropwise added a solution of m-chloroperbenzoic acid (15.1 g, 87.6 mmol) in methanol (15 mL). After being stirred for 5 h, methanol was removed in vacuo and the white residue was dissolved in methylene chloride (300 mL). To the solution was added K2CO3. The resulting solution was stirred for 1 h and filtered through celite. The filtrate was evaporated in vacuo to provide the desired product which was used directly for the next reaction without purification. methanol was removed in vacuo the white residue was dissolved in methylene chloride (300 mL) To the solution was added K2CO3 The resulting solution was stirred for 1 h filtered through celite The filtrate was evaporated in vacuo

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

Procedure: A suspension of 2,3-dihydroxy-4-methoxybenzoic acid (6.04 g, 32.8 mmol) in 5,6-dihydro-4-methoxy-2H-pyran (20 mL, 152 mmol) was kept at 140° C. for three days. At room temperature ethyl acetate (200 mL) was added and the organic phase was extracted with saturated aqueous NaHCO3 (2×50 mL). The aqueous phase was washed with Et2O (2×40 mL), acidified to pH=1 with concentrated HCl and extracted with dichloromethane (2×50 mL). The organic phase was dried over MgSO4. Evaporation under reduced pressure afforded traces of 2,3-dihydroxy-4-methoxybenzoic acid along with 7-methoxy-2′,3′,5′,6′-tetrahydro-Spiro[1,3-benzodioxole-2,4′-(4H)-pyran]-4-carboxylic acid (1.23 g, 14%). 13C NMR (DMSO) δ 164.9, 148.2, 146.6, 134.5, 123.7, 117.0, 107.1, 106.8, 64.4, 56.0, 35.3. the organic phase was extracted with saturated aqueous NaHCO3 (2×50 mL) The aqueous phase was washed with Et2O (2×40 mL) extracted with dichloromethane (2×50 mL) The organic phase was dried over MgSO4 Evaporation under reduced pressure

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

Procedure: To a solution of 4-methoxy-3,6-dihydro-2H-pyran (5.00 g, 43.8 mmol) in methanol (100 mL) at 0° C. was dropwise added a solution of m-chloroperbenzoic acid (15.1 g, 87.6 mmol) in methanol (15 mL). After being stirred for 5 h, methanol was removed in vacuo and the white residue was dissolved in methylene chloride (300 mL). To the solution was added K2CO3. The resulting solution was stirred for 1 h and filtered through celite. The filtrate was evaporated in vacuo to provide the desired product which was used directly for the next reaction without purification. methanol was removed in vacuo the white residue was dissolved in methylene chloride (300 mL) To the solution was added K2CO3 The resulting solution was stirred for 1 h filtered through celite The filtrate was evaporated in vacuo

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

Procedure: To a solution of 4-methoxy-3,6-dihydro-2H-pyran (5.00 g, 43.8 mmol) in methanol (100 mL) at 0° C. was dropwise added a solution of m-chloroperbenzoic acid (15.1 g, 87.6 mmol) in methanol (15 mL). After being stirred for 5 h, methanol was removed in vacuo and the white residue was dissolved in methylene chloride (300 mL). To the solution was added K2CO3. The resulting solution was stirred for 1 h and filtered through celite. The filtrate was evaporated in vacuo to provide the desired product which was used directly for the next reaction without purification. methanol was removed in vacuo the white residue was dissolved in methylene chloride (300 mL) To the solution was added K2CO3 The resulting solution was stirred for 1 h filtered through celite The filtrate was evaporated in vacuo