See, Ma, Jianxun and Chen, Bin; Yingyong Huagong, 36(7), 732-733, 736; 2007
" The fluorescent whitening agent OB was prepd. from thiophene-2,5-dicarboxylic acid and 2-amino-4-tert-Bu phenol. The synthetic methods were investigated, and the influence of various solvents and their addn. amt. on the yield of product were discussed particularly. The optimum solvent was phenyl-trichloride with addn. amt. of 2 L/mol of thiophene-2,5-dicarboxylic acid, and toluene was added as the auxiliary solvent during refluxing. The reaction was properly catalyzed in N2 atmosphere and carried out in two stages of different temps. resp. at 140-150° and 210-220°. Under such conditions, the yield of fluorescent whitening agent OB (m.p.:200-201°) was more than 86% with purity of 99%. "
Also
Method for preparing 2,5-bis(5-tert-butylbenzoxazol-2-yl)thiophene; Ma, Xuewen; Faming Zhuanli Shenqing, 102070627, 25 May 2011