**3. Conclusions**

We have described the synthesis of novel aryl-substituted homophthalic acids. Their cyclodehydration to the respective homophthalic anhydrides and the Castagnoli–Cushman reaction of the latter with a range of imines resulted in good yields and delivered hitherto undescribed 4-aryl-substituted tetrahydroisoquinolonic acids with remarkable diastereoselectivity, good yields and no need for chromatographic purification. These products are distinct in that they contain an all-carbon quaternary stereogenic centers in the α-position to the carboxylic acid. The cyclodehydration–Castagnoli–Cushman reaction protocol was found to be also transferrable to a novel 1,2,3-triazol-1-yl-substituted homophthalic acid. These findings significantly extend the range of cyclic anhydrides employable in the Castagnoli–Cushman reaction and signify access to a novel substitution pattern around the medicinally relevant tetrahydroisoquinolonic acid scaffold.
