The translation to non-symmetrical dienes poses additional aspects that hinder reaction selectivity (Figure 1B, top). Upon excitation, site-selectivity of a specific alkene is a consideration, while competing reactivity can lead to reaction divergence, such as, uncontrolled "alkene scrambling", via geometric isomerization, and 4+2 cycloaddition via reactivity at both termini of the diene. The result is a complex distribution of products that is challenging to modulate both photochemically or via EnT. To regulate selectivity, the design of noncovalent interactions is ambitious as reaction pathways are intimately linked to intrinsic reactivity and excited state properties of the system. When considering triplet excited states spin density is often leveraged as a predictive tool for regioselectivity with great effect, 14 however, application with non-symmetrical dienes is comparatively underexplored. The strategic incorporation of a single unit that can be systematically tuned to display contrasting reactivity would be highly enabling to probe spin density and competing reaction pathways, providing a user's guide for future reaction design of non-symmetrical diene systems.