Synthesis of Benzoxazoles Containing Allyl Crosslinking Sites via Claisen Rearrangements

The reaction of diethyl 2,5-dihydroxyterephthalate with allyl bromide/K2CO3 in DMF followed by hydrolysis provided 2,5-di(allyloxy)terephthalic acid. The conversion of 2,5-di (allyloxy)terephthalic acid to 1,4-di(2-benzoxazolyl)-2,5-di(allyloxy)benzene in PPSE was unsuccessful. However, the reaction of 1,4-di(2-benzoxazolyl)-2,5- dihydroxybenzene with allyl bromide/K2CO3 provided 1,4-di(2-benzoxazolyl)-2,5- di(allyloxy)benzene. DSC analysis indicated that 1,4-di(2-benzoxazolyl)-2,5- di(allyloxy)benzene undergoes a Claisen rearrangement to the corresponding diallyl product. The synthesis of 2-allyloxy-1,4-di(2-benzoxazolyl)benzene was carried out using 2-hydroxy-1,4-di(2-benzoxazolyl)benzene as starting material. DSC analysis was inconclusive with respect to a Claisen rearrangement. The reaction of 2-allyloxybenzoic acid with 2,2-bis(3-amino-4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane in PPSE was unsuccessful but the reaction of 2,2-bis(2-(2-hydroxyphenyl)-5-benzoxazolyl)-1,1,1,3,3,3-hexafluoropropane with allyl bromide/K2CO3 in DMF provided 2,2-bis(2-(2- allyloxyphenyl)-5-benzoxazolyl)-1,1,1,3,3,3-hexafluoropropane. DSC analysis of 2,2- bis(2-(2-allyloxyphenyl)-5-benzoxazolyl)-1,1,1,3,3,3-hexafluoropropane was inconclusive as to the presence of a Claisen rearrangement