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Disclosed here is a palladium‐catalyzed direct [4+1] spiroannulation of ortho‐C−H bonds of naphthols with cyclic diaryliodonium salts to construct spirofluorenyl naphthalenones (SFNP) under mild reaction conditions. This spiroannulation directly transforms the hydroxy group into a carbonyl group, and also tolerates reactive functional groups such as the halo groups, which provide an opportunity to rapidly assemble structurally new thermally activated delayed fluorescent (TADF) materials that feature a carbonyl group with an adjacent spirofluorenyl unit as the acceptor. As an illustrated example, the OLED device utilizing the assembled DMAC‐SFNP as the host material exhibits a low turn‐on voltage of 2.5 V and an ultra‐high external quantum efficiency of 32.2 %. This work provides inspiration for structurally new TADF materials, and also displays the potential of C−H activation as a synthetic strategy for the innovation of optoelectronic materials. [ABSTRACT FROM AUTHOR]

We demonstrate the first compact photonic flywheel with sub-fs time jitter (averaging times up to 10  μs) at the quantum-noise limit of a monolithic fiber resonator. Such quantum-limited performance is accessed through novel two-step pumping scheme for dissipative Kerr soliton generation. Controllable interaction between stimulated Brillouin lasing and Kerr nonlinearity enhances the DKS coherence and mitigates the thermal instability challenge, achieving a remarkable 22-Hz intrinsic comb linewidth and an unprecedented phase noise of -180  dBc/Hz at 945-MHz carrier at free running. The scheme can be generalized to various device platforms for field-deployable precision metrology.

A highly efficient palladium-catalyzed direct C-H functionalization/annulation of BODIPYs with alkynes has been developed for the first time to construct a series of unsymmetrical benzo[ b]-fused BODIPYs from readily available starting materials. These unsymmetrical benzo[ b]-fused BODIPYs exhibit remarkably red-shifted emissions and larger Stokes shifts than classical BODIPY dyes. Cell imaging experiments and cytotoxicity assays demonstrate that BODIPYs 4c and 4d have specific lysosome-labeling capacities, turn-on fluorescence emissions in cells, and low cytotoxicity.

An Ir(III)-catalyzed oxidative annulation of phenylglyoxylic acids with benzo[ b]thiophenes for the construction of benzothieno[3,2- c][2]benzopyranones in one step is disclosed. Three C-H cleavages and C-C/C-O bond formations are involved in this reaction. This protocol features a relatively broad substrate scope, good functional group tolerance, good regioselectivities, mild reaction conditions, and scale-up synthesis.