Example 116
X-Phodamine PH-sensor 162. Aldehyde 159 (0.336 g, 1.0 mmol), 8-hydroxyjullolidine (0.416 g, 2.2 mmol), and 10-camphorsulfonic acid (20 mg, catalyst) were stirred for 18 h in propionic acid (10 mL) at 65-70° C., cooled to rt and poured into aqueous 3N NaOAc (200 mL) and sat. NaHCO3 (10 mL). The mixture was extracted with CHCl3 (7×40 mL), extract was washed with brine (200 mL), filtered through paper filter, and evaporated to give a crude dihydro derivative 161. A sample of this compound (40 mg, 0.06 mmol) was vigorously stirred in CHCl3 (50 mL) with Bengal Rose (10 mg, catalyst) in an open beaker under the sunlamp illumination for 18 h. After evaporation the residue was purified by preparative TLC on two silica gel plates using 7% H2O in MeCN as eluant to give compound 162 (11 mg, 24%) as a dark red solid.
