Manipulation of reactive chromophores to direct their excited state energy towards a desired pathway is quintessential in designing new photochemical reactions. This involves altering the traditional reactivity by understanding the rates of different deactivation pathways from the excited state, and hence carefully designing the molecule to control the reactive intermediate formed during the photochemical process. Traditionally 1,3-dicarbonyl compounds are known to undergo <i>De Mayo</i> reaction with alkenes to give 1,5 diketones. We envisioned that we could alter the course of this photoreaction if we activate the alkene. We synthesized amino alkenes which on reacting with a 1,3-dicarbonyl compound, resulted in the formation of an enaminone, which further underwent the photoreaction giving access to bicyclo-dihydropyrans. In a single step we were able to showcase that using light we can convert planar reactants to complex heterocyclic structure with a complex stereochemistry. The synthesized photoproduct which was confirmed with single crystal XRD can give convenient access to the core of Marmycin, which is cancer drug candidate showing cytotoxicity against several cancer cell lines. Conventional synthesis of Marmycin involves multistep thermal synthesis. With our strategy we can access the core structure of Marmycin in a single step using light with good isolated yields. Preliminary photophysical investigations reveal that the enaminone on excitation first undergoes an excited state proton transfer, which further cyclizes, and rearomatize to give the photoproduct.

Exploiting excited state processes to uncover new photochemical reactivity by changing the course of the De Mayo reaction

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.