Exploration of the Reactivity and Applications of Diazo Arylidene Succinimides (DAS) under Visible Light and Metal Catalysis

Abstract

Diazo compounds are highly versatile as well as valuable reagents whose reactivity can be fine-tuned through metal catalysis, photochemical activation, and radical pathways to enable divergent and selective synthetic transformations. This thesis has investigated the novel reactivity of diazo arylidene succinimides (DAS) under different reaction conditions and developed innovative synthetic methodologies with mechanistic insights in great detail. dirhodium(II)-catalyzed regio-divergent rearrangement of allyloxy/thioallyl containing DAS derivatives enabled the sigmatropic shifts to construct chromene and thiochromene scaffolds. Different DAS derivatives have been employed for a copper-catalyzed radical cyclization via a photoinduced proton-coupled electron transfer (PCET) mechanism to access the disubstituted pyromellitic diimides (PMDIs). This transformation was driven via a carbenefree pathway and novel radical reactivity of DAS was explored in presence of copper and visible light. Further expanding the photochemical reactivity of DAS, 1,3-dibromination has been accomplished using N-bromosuccinimide (NBS) via radical pathway to access bromofunctionalized DAS derivatives under the exposure of visible light. The method did not rely on an photocatalysts or any additives and also worked under the direct exposure of natural sunlight. Additionally, a photochemical O–H functionalization has been accomplished and, in this method, methanol has been utilized as a key component in this photoinduced proton transfer (PPT) processes. The reactivity of DAS specific to the methanol under visible light conditions has been demonstrated. This diversifying the O-H functionalization landscape of DAS. These studies highlight the use of metal catalysis as well as photocatalysis to explore novel reactivity of diazo compounds. The radical reactivity of DAS has been explored under visible light conditions to access useful compounds. The developed methods provide efficient and scalable strategies for building complex molecules, with promising applications in modern organic chemistry.