Trifluoroacetic acid → (2E)-3-{4-[Cyclopentylidene(4-hydroxyphenyl)methyl]phenyl}-2-propenoic acid

Participants

Reaction Steps

To an ice-water cooled solution of 1,1-dimethylethyl(2E)-3-{4-[cyclopentylidiene(4-hydroxyphenyl)methyl]phenyl}-2-propenoate (4) (0.28 g, 0.74 mmol) in dichloromethane (5 mL) was slowly added trifluoroacetic acid (5 mL) with stirring under a nitrogen atmosphere. After 1 h, the reaction mixture was concentrated in vacuo to give a solid. The solid was dissolved in dichloromethane and the solution was concentrated in vacuo to give a pale tan solid. The solid was triturated with diethyl ether and filtered to give the acrylic acid as an off-white solid. The solid was dried overnight under vacuum at 70° C., however, 1H NMR indicated that solvent remained in the sample. The solid was dissolved in methanol and the solution was concentrated in vacuo to give an oil. The oil was dissolved in methanol and the solution was concentrated in vacuo under high vacuum at 60° C. to give an oil. Dichloromethane was added to the oil and crystallization was induced with the aid of a spatula. The suspension was filtered and the solid was dried in a vacuum oven overnight at 70° C. to give 0.072 g (30%) of compound 5 as a yellow solid. 1H NMR (400 MHz, DMSO-d6): δ 1.60 (m, 4 H), 2.30 (m, 4 H), 6.44 (d, J=15.9 Hz, 1 H), 6.67 (d, J=8.4 Hz, 2 H), 6.90 (d, J=8.4 Hz, 2 H), 7.13 (d, J=8.2 Hz, 2 H), 7.53 (d, J=15.9 Hz, 1 H), 7.57 (d, J=8.3 Hz, 2 H), 9.32 (s, 1 H). The compound was silated prior to EI analysis. HRMS (EI) Calcd for C27H36Si2O3: 464.2203 (M+). Found: 464.2210.

Provenance & Evidence