Acetone → Methyl 2-methylazulene-1-carboxylate

Participants

Reaction Steps

2-Methylazulene was synthesized in accordance with the method described in Japanese Laid-Open Patent Publication No. 207232/1987. Thus, 19.5 g (0.16 mol) of tropolone and 40 g (0.21 mol) of p-toluenesulfonic acid chloride were reacted with each other in pyridine to obtain 37.1 g of tosylated tropolone. This compound was then reacted with 20 g (0.15 mol) of dimethyl malonate and 9.7 g (0.18 mol) of NaOMe in methanol at room temperature for four hours to obtain 14.4 g of 3-methoxy-carbonyl-2H-cyclohepta(b)furan-2-one (compound (2)). To 12 g of the compound (2) were added 200 ml of acetone and 70 ml of diethylamine, and the mixture was refluxed for 30 hours. Water was added to this mixture, and the resulting mixture was extracted with toluene to obtain 39.2 g of methyl-2-methyl-azulenecarboxylate. To this compound was further added 25 ml of phosphoric acid, and reaction was carried out at a temperature of 85 to 90° C. for one hour. The reaction mixture was subjected to decomposition with water, and the resultant was extracted with benzene. The organic phase was dried to obtain 6.5 g of the desired compound, 2-methylazulene.

Provenance & Evidence