Synthesis
1. Synthesis of 2,3-dihydrobenzo[b]furan-7-carboxylic acid (15a): N,N,N',N'-tetramethylethylenediamine (TMEDA) (24.3 g, 0.21 mol) was added dropwise to a solution of n-BuLi (1.7 M, 123 mL, 0.21 mol) in 400 mL of hexanes under argon protection followed by the addition of a solution of 2,3-dihydrobenzo[b ] furan (14) (12.56 g, 0.11 mol) solution in hexane (40 mL). The reaction mixture was stirred at room temperature for 4 hours. The reaction mixture was slowly poured into dry ice pre-washed with anhydrous ether, followed by stirring at room temperature overnight. After completion of the reaction, the organic and aqueous layers were separated by diluting the mixture with 300 mL of water. The aqueous layer was acidified to pH 1 with concentrated hydrochloric acid and precipitated as a white solid upon cooling. The precipitate was collected by filtration and recrystallized with dichloromethane (CH2Cl2) to give the target product 15a (9.43 g, 54.7% yield) as a white solid with a melting point of 167-169.5 °C.
References
[1] Patent: US4888353, 1989, A
[2] Patent: EP234872, 1991, B1
[3] Patent: US5122361, 1992, A
