The general procedure for the synthesis of 2-hydroxy-[1,1'-biphenyl]-3-carbaldehyde from formaldehyde and o-phenylphenol was as follows: o-phenylphenol (300 mmol, 51 g) was dissolved in tetrahydrofuran (THF, 400 mL), followed by the addition of triethylamine (3.5 equiv, 145 mL) and magnesium dichloride (1.5 equiv, 43 g). Paraformaldehyde (6.0 eq., 54 g) was added in batches over 10 min, taking care to control the rate of addition to avoid intense exotherm, and the reaction mixture gradually turned yellow. The resulting yellow mixture was gently refluxed for 1.5 hours. The progress of the reaction was monitored by thin layer chromatography (TLC, Spreader: 20% ethyl acetate/hexane) to confirm that the o-phenylphenol was completely consumed and a more hydrophobic target product was produced (Rf = 0.44). Upon completion of the reaction, the mixture was cooled in an ice bath and the pH was adjusted with 3N hydrochloric acid to about 5. The acidified reaction solution was extracted with ether or ethyl acetate, the organic layers were combined, washed sequentially with water and brine, and dried over anhydrous sodium sulfate. The dried organic phase was concentrated under reduced pressure to give the oily product 2-hydroxy-[1,1 '-biphenyl]-3-carbaldehyde (54.6 g, 92% yield). The product was analyzed by high performance liquid chromatography (HPLC, detection wavelength 254 nm, mobile phase: 1-90% acetonitrile/water containing 0.05% trifluoroacetic acid) with a retention time of 8.8 min. Nuclear magnetic resonance hydrogen spectroscopy (1H NMR, 300 MHz, CDCl3) data were as follows: δ 11.6 ppm (s, 1H), 10.0 ppm (s, 1H), 7.7-6.9 ppm (m, 7H).
![2-Hydroxy-[1,1'-biphenyl]-3-carbaldehyde](/CAS/20150408/GIF/14562-10-8.gif)