Synthesis of 4-(2-arylvinyl)-8-hydroxyquinolines via anhydrous Heck coupling reaction and the PL properties of their Al complexes

Anhydrous Heck coupling between 2 and eight different arylvinyl compounds using 3 mol % of PdCl2/2PPh3 catalyst system occurs selectively at position-4 of 2 affording 4-(2-arylvinyl)-8-tosyloxyquinolines 3 in good to high yields. The tosyloxy protecting group showed high stability under anhydrous coupling conditions. Deprotection of the resulting 4-arylvinyl-8-tosyloxyquinolines produced 4-(2-arylvinyl)-8-hydroxyquinolines 4 in high yields. The aluminium complexes of the resulting 8-hydroxyquinolines have been synthesized and their photoluminescence (PL) properties have been studied. One of the complexes with a 2,4,6-trimethoxystyryl substituent at position-4 of the quinolate shows higher relative PL quantum yield than the other complexes due to the minimization of the cis–trans photoisomerization in solution.