Methyl 4-Formylbenzoate → Methyl 4-(2-methoxyethenyl)benzoate

Participants

Reaction Steps

To a suspension of methoxymethyltriphenylphosphonium chloride (6.366 g, 18.5 mmol) in dry tetrahydrofuran (50 ml) under argon atmosphere at −78° C. slowly (ca. for 5 minutes) a 2.46 N solution of potassium tert-butoxide in tetrahydrofuran (8.2 ml, 20.2 mmol) was added and the reaction mixture was stirred at this temperature for 1 hour. A solution of methyl 4-formylbenzoate (6a) (2.531 g, 15.4 mmol) in tetrahydrofuran (10 ml) was added to the reaction mixture and the resultant suspension was stirred at −78° C. for 30 minutes. The cooling bath was removed and the reaction mixture was stirred for 30 minutes allowing warming up to room temperature. The mixture was partitioned between benzene (150 ml) and water (150 ml), and the organic layer was washed successively with water (150 ml), brine (50 ml), and dried (Na2SO4). The solvent was evaporated and the residue was chromatographed on silica gel (100 g) with toluene-triethylamine (100:0.25) as eluent to give the title compound (2.696 g, 91%) as a mixture of E and Z isomers (ca. 95:5). (E)-(7a): 1H NMR (CDCl3, HMDSO) δ: 3.67 (3H, s); 3.86 (3H, s); 5.81 (1H, d, J=13.5 Hz); 7.14 (1H, d, J=13.5 Hz); 7.25 (2H, d, J=8.5 Hz); 7.89 (2H, d, J=8.5 Hz). A small additional singlet at 3.80 ppm and 2 doublets at 5.23 (d, J=7.6 Hz); 6.22 ppm (d, J=7.6 Hz) in the 1H NMR spectrum of 7a was attributed to minor amounts (ca. 5%) of (Z)-(7a) isomer present in the product.

Provenance & Evidence