3,3-dimethyl-2H-chromen-4-one

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

Procedure: To a cooled (−78° C. bath temperature) solution of 2,3-dihydro-4H-chromen-4-one (25 grams, 0.169 mole) and iodomethane (120 grams, 53 ml, 0.945 mole) in anhydrous tetrahydrofuran (1000 ml) was added portion-wise potassium tertiary butoxide (94.5 grams, 0.945 mole) over a period of 1 hour under an argon atmosphere. During this process, the reaction temperature was kept at −78° C. to avoid exothermic reaction. The cooling bath was removed, and the resulting mixture was warmed to room temperature over a period of 4 hours. The white viscous mixture was heated at 60° C. (bath temperature) for 4 hours, cooled to room temperature, and stirred at room temperature for 15 hours. The resulting mixture was poured into a mixture of diethyl ether and water. The organic layer was separated, and the aqueous layer was extracted with diethyl ether. The combined extracts were washed with saturated sodium chloride aqueous solution, dried over sodium sulfate, and concentrated. The residue was chromatographed (silica gel, elution by methylene chloride) to give 30 grams (100%) of 3,3-dimethyl-2,3-dihydro-4H-chromen-4-one as a clear pale yellow oil. Physical properties of the product were the same as those described in Example 3. was kept at −78° C. reaction The cooling bath was removed The white viscous mixture was heated at 60° C. (bath temperature) for 4 hours cooled to room temperature The resulting mixture was poured into a mixture of diethyl ether and water The organic layer was separated the aqueous layer was extracted with diethyl ether The combined extracts were washed with saturated sodium chloride aqueous solution dried over sodium sulfate concentrated The residue was chromatographed (silica gel, elution by methylene chloride)

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

Procedure: To a cooled (−78° C. bath temperature) solution of 2,3-dihydro-4H-chromen-4-one (25 grams, 0.169 mole) and iodomethane (120 grams, 53 ml, 0.945 mole) in anhydrous tetrahydrofuran (1000 ml) was added portion-wise potassium tertiary butoxide (94.5 grams, 0.945 mole) over a period of 1 hour under an argon atmosphere. During this process, the reaction temperature was kept at −78° C. to avoid exothermic reaction. The cooling bath was removed, and the resulting mixture was warmed to room temperature over a period of 4 hours. The white viscous mixture was heated at 60° C. (bath temperature) for 4 hours, cooled to room temperature, and stirred at room temperature for 15 hours. The resulting mixture was poured into a mixture of diethyl ether and water. The organic layer was separated, and the aqueous layer was extracted with diethyl ether. The combined extracts were washed with saturated sodium chloride aqueous solution, dried over sodium sulfate, and concentrated. The residue was chromatographed (silica gel, elution by methylene chloride) to give 30 grams (100%) of 3,3-dimethyl-2,3-dihydro-4H-chromen-4-one as a clear pale yellow oil. Physical properties of the product were the same as those described in Example 3. was kept at −78° C. reaction The cooling bath was removed The white viscous mixture was heated at 60° C. (bath temperature) for 4 hours cooled to room temperature The resulting mixture was poured into a mixture of diethyl ether and water The organic layer was separated the aqueous layer was extracted with diethyl ether The combined extracts were washed with saturated sodium chloride aqueous solution dried over sodium sulfate concentrated The residue was chromatographed (silica gel, elution by methylene chloride)

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

Procedure: To a cooled (−10 to 0° C. bath temperature) solution of 2,3-dihydro-4H-chromen-4-one (8.0 grams, 0.054 mole) and iodomethane (22.8 grams, 10 ml, 0.16 mole) in anhydrous tetrahydrofuran (150 ml) was added portion-wise potassium tertiary butoxide (30 grams, 0.27 mole) under an argon atmosphere. During this process, the temperature was kept between −10 to 0° C. to avoid exothermic reaction. The cooling bath was removed, and the resulting mixture was warmed to room temperature. The mixture was heated at 60° C. for 4 hours, heated at reflux for 1 hour, and cooled to room temperature. Additional iodomethane (16 grams, 7 ml, 0.11 mole) was added, and heating was repeated at 60° C. for 4 hours and at reflux for 1 hour. The cooled solution was poured into a mixture of diethyl ether and water. The organic layer was separated, and the aqueous layer was extracted with diethyl ether. The combined extracts were washed with saturated sodium chloride aqueous solution, dried over sodium sulfate, and concentrated. The residue was chromatographed (silica gel, elution by methylene chloride) to give 5.62 grams (59.1%) of 3,3-dimethyl-2,3-dihydro-4H-chromen-4-one as a clear pale yellow oil. was kept between −10 to 0° C. reaction The cooling bath was removed The mixture was heated at 60° C. for 4 hours heated at reflux for 1 hour cooled to room temperature heating at reflux for 1 hour The organic layer was separated the aqueous layer was extracted with diethyl ether The combined extracts were washed with saturated sodium chloride aqueous solution dried over sodium sulfate concentrated The residue was chromatographed (silica gel, elution by methylene chloride)

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

Procedure: To a cooled (−10 to 0° C. bath temperature) solution of 2,3-dihydro-4H-chromen-4-one (8.0 grams, 0.054 mole) and iodomethane (22.8 grams, 10 ml, 0.16 mole) in anhydrous tetrahydrofuran (150 ml) was added portion-wise potassium tertiary butoxide (30 grams, 0.27 mole) under an argon atmosphere. During this process, the temperature was kept between −10 to 0° C. to avoid exothermic reaction. The cooling bath was removed, and the resulting mixture was warmed to room temperature. The mixture was heated at 60° C. for 4 hours, heated at reflux for 1 hour, and cooled to room temperature. Additional iodomethane (16 grams, 7 ml, 0.11 mole) was added, and heating was repeated at 60° C. for 4 hours and at reflux for 1 hour. The cooled solution was poured into a mixture of diethyl ether and water. The organic layer was separated, and the aqueous layer was extracted with diethyl ether. The combined extracts were washed with saturated sodium chloride aqueous solution, dried over sodium sulfate, and concentrated. The residue was chromatographed (silica gel, elution by methylene chloride) to give 5.62 grams (59.1%) of 3,3-dimethyl-2,3-dihydro-4H-chromen-4-one as a clear pale yellow oil. was kept between −10 to 0° C. reaction The cooling bath was removed The mixture was heated at 60° C. for 4 hours heated at reflux for 1 hour cooled to room temperature heating at reflux for 1 hour The organic layer was separated the aqueous layer was extracted with diethyl ether The combined extracts were washed with saturated sodium chloride aqueous solution dried over sodium sulfate concentrated The residue was chromatographed (silica gel, elution by methylene chloride)