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The fusion of tetrapyrroles with aromatic heterocycles constitutes a useful tool for manipulating their opto‐electronic properties. In this work, the synthesis of naphthodithiophene‐fused porphyrins was achieved through a Heck reaction‐based cascade of steps followed by the Scholl reaction. The naphthodithiophene‐fused porphyrins display a unique set of optical and electronic properties. Fusion of the naphtho[2,1‐b:3,4‐b’]dithiophene to porphyrin (F2VTP) leads to a ~20% increase in the fluorescence lifetime, which is accompanied, unexpectedly, by a more than two‐fold drop in the emission quantum yield (ϕ=0.018). In contrast, fusion of the isomeric naphtho[1,2‐b:4,3‐b’]dithiophene to porphyrin (F3VPT)results in a ~1.5‐fold increase in the fluorescence quantum yield (ϕ=0.13) with a concomitant ~30 % increase in the fluorescence lifetime. This behavior suggests that fusion of the porphyrin with the naphthodithiopheno‐system mainly affects the radiative rate constant in the Q‐state deactivation pathway, where the effects of the isomeric naphtho[2,1‐b:3,4‐b’]dithiophene‐ versus naphtho[1,2‐b:4,3‐b’]dithiophene‐fusion are essentially the opposite. Interestingly, nucleus‐independent chemical shifts analysis revealed a considerable difference between the aromaticities of these two isomeric systems. Our results demonstrate that subtle structural differences in the fused components of the porphyrin can be reflected in rather significant differences between the photophysical properties of the resulting systems.

 

A double divergent process has been developed for the reaction of α-enaminones with quinones through facile manipulation of catalyst and additive, leading to structurally completely different products. The two divergent processes, which involve formal aza- and oxo-[3 + 2] cycloaddition reactions, are mediated by chiral phosphoric acid and molecular sieves, respectively. While inclusion of phosphoric acid in the reaction switched the reaction pathway to favor the efficient formation of a wide range of N -substituted indoles, addition of 4 Å molecular sieves to the reaction switched the reaction pathway again, leading to enantioselective synthesis of 2,3-dihydrobenzofurans in excellent yields and enantioselectivities under mild conditions. Studies in this work suggest that the chiral phosphoric acid acts to lower the transition state energy and promote the formation of amide intermediate for the formal aza-[3 + 2] cycloaddition and the molecular sieves serve to facilitate proton transfer for oxo-[3 + 2] cycloaddition. The reactivity of α-enaminones is also disclosed in this work.