反应详情

In SCHEME 9 3,4-dimethoxyphenol (36) is selectively nitrated with 70% HNO3 in AcOH to give 4,5-dimethoxy-2-nitrophenol (37) which is further converted to the corresponding triflate (38) with trifluoromethylsulfonic anhydride (Tf2O) and pyridine in dichloromethane. Triflate (38) is reacted under inert conditions with a boronic acid of general type (31) under Suzuki-type basic conditions (Pd(PPh3)4 and aqueous potassium phosphate in toluene) to a biaryl of type (39). Biaryl (39) is further hydrolized with aqueous lithium hydroxide in THF and MeOH or MeCN to give the corresponding carboxylic acid (40) which is converted to a building block of type (41) by reaction with oxalyl chloride in anhydrous dichloromethane.