Unexpected Performance of a Bifunctional Sensitizer/Activator Component for Photon Energy Management via Upconversion.

We here report on the observation of upconverted photoluminescence (UC-PL) from the blue-light-emitting 9,10-diphenylanthracene (DPA) mixed with the yellow-light-absorbing bifunctional sensitizer/activator component of (3,3,7,8,12,13,17,18-octaethylporphyrin-22,24-diid-2-one) Pt (PtOEP-K). Yellow-to-blue UC-PL (0.680 eV spectral upshift) is achieved at room temperature under ultralow power continuous incoherent photoexcitation (220 μW/cm) despite the absence of triplet energy transfer (TET) between PtOEP-K and DPA.

Synthesis of Canthin-4-ones and Isocanthin-4-ones via B Ring Construction.

Canthin-4-one is synthesized via a six-step procedure starting from commercially available 3-amino-4-bromopyridine in 26% overall yield. 3-Amino-4-bromopyridine is initially converted to 8-bromo-1,5-naphthyridin-4(1)-one. O-Methylation, intermolecular Pd-catalyzed C-C coupling, and demethylation afford the key intermediate, 8-(2-chlorophenyl)-1,5-naphthyridin-4(1)-one, for which intramolecular C-N coupling completes the synthesis of the canthin-4-one skeleton.

The Photochemical Mediated Ring Contraction of 4-1,2,6-Thiadiazines To Afford 1,2,5-Thiadiazol-3(2)-one 1-Oxides.

1,2,6-Thiadiazines treated with visible light and O under ambient conditions are converted into difficult-to-access 1,2,5-thiadiazole 1-oxides (35 examples, yields of 39-100%). Experimental and theoretical studies reveal that 1,2,6-thiadiazines act as triplet photosensitizers that produce O and then undergo a chemoselective [3 + 2] cycloaddition to give an endoperoxide that ring contracts with selective carbon atom excision and complete atom economy. The reaction was optimized under both batch and continuous-flow conditions and is also efficient in green solvents.