Synthesis of Unique Scaffolds via Diels−Alder Cycloadditions of Tetrasubstituted Cyclohexadienes

Diels−Alder cycloadditions of highly substituted cyclohexadienes derived from rhodium-mediated [2 + 2 + 2] cyclizations are reported. Reactive heterodienophiles, including singlet oxygen (¹O₂), 4-substituted-1,2,4-triazoline-3,5-diones (TADs), and aryl- and acylnitroso compounds were employed, yielding novel heterocyclic products.