Synthesis of cycloalkynes via photochemical decarboxylation of ω-phthalimidoalkynoates

The photodecarboxylation reactions of ω-phthalimidoalkynoates have been studied and the influence of the geometrically restricted acetylene linker on the photocyclization efficiency investigated. Less flexible starting materials give solely CO₂H/H-exchange products in good yields. In contrast, derivatives with appropriate chain lengths give the corresponding macrocycles in fair to moderate isolated yields. Furthermore, photodecarboxylative addition of alkynoates to N-methylphthalimide gives hydroxyphthalimidines in acceptable yields.