2-methyl- (CAS NO.: ), which is also known as 4H-Pyran-4-one, 2-methyl-, could be produced through the following synthetic routes.

A. 5-(1-Hydroxyethylidene)- (CAS NO.: ). A flame-dried, 500-mL, three-necked, round-bottomed flask is equipped with a stir bar, nitrogen inlet adapter, and a pressure-equalizing addition funnel fitted with a rubber septum. The flask is charged with 22.0 g of dissolved in 153 mL of methylene chloride , and 24.8 mL of pyridine, and the mixture is cooled to -25°C. A mixture of 18.3 mL of methylene chloride and 13.1 mL of acetyl chloride is slowly added to the reaction mixture via the addition funnel over 1 hr. After the addition of the acetyl chloride is complete, the reaction is slowly warmed over 3 hr to 0°C. (30 mL) is added to quench the reaction and stirring is continued for 15 min. The reaction mixture is transferred to a 2000-mL separatory funnel, diluted with 100 mL of methylene chloride and washed with saturated aqueous ammonium chloride (3 × 140 mL) and 140 mL of water. The aqueous layers are combined and extracted with methylene chloride (3 × 100 mL). The combined organic layers are dried over 200 g of sodium sulfate for 3 hr. The solution is filtered into a 1000-mL, round-bottomed flask and the methylene chloride is removed under reduced pressure. The residual orange solid can be purified by breaking up the solid into a fine powder with a mortar and pestle and placing it under vacuum overnight to remove any remaining pyridine to yield 26.0 g of acylated Meldrum's acid suitable for use in the next step.

B. and C. 2-Methyl-4H-pyran-4-one (CAS NO.: ). A 1000-mL, round-bottomed flask equipped with a stir bar and a reflux condenser is charged with the crude acylated Meldrum's acid, 80 mL of butyl vinyl ether and 287 mL of toluene (or benzene ). The reaction mixture is heated to 80°C for 7 hr. The volatile components are removed under reduced pressure to yield 31.81 g of product. To the residue are added 765 mL of tetrahydofuran , 191 mL of water and 2.7 g of p-toluenesulfonic acid . The mixture is heated to reflux for 18 hr, then the reaction is quenched with 10 g of solid sodium bicarbonate and allowed to stir for 15 min at 25°C. The mixture is filtered to remove the sodium bicarbonate and the volatile components are removed under reduced pressure. The residue is dissolved in 500 mL of methylene chloride , placed in a separatory funnel and washed with 200 mL of water and 200 mL of brine solution. The aqueous layers are collected and extracted with methylene chloride (2 × 200 mL). The organic layers are combined, dried over 20 g of sodium sulfate for 1 hr, filtered into a 1000-mL, round-bottomed flask, and concentrated under reduced pressure. The resulting red oil is purified by chromatography using a 6-cm diameter glass column packed with 400 g of silica gel with 2.5% methanol/methylene chloride as the eluant yielding 5.25-5.81 g (38.6-42.7%) of 2-methyl-4H-pyran-4-one.