Palladium-Catalyzed Cycloisomerization of 2-Ethynylbiaryls to 9-Methylidene Fluorenes

Synthesis, Structures and Photophysical Properties of Asymmetric Fulvene-[b]-fused BODIPYs

Herein, we developed a one-pot procedure to synthesize novel fulvene-[b]-fused BODIPYs from α-(2-alkynylphenyl)-pyrrole and acylpyrrole, using 5-exo cyclization as the key transformation. Compared to benzene-[b]-fused BODIPYs, although they have similar chemical compositions, their structures and properties significantly differ from each other, which can be attributed to the less aromaticity of the fulvene linker than benzene. Notably, fulvene-[b]-fused BODIPY 1 b exhibits helical-twisted core skeleton, intensified red-shifted absorption, and peak fluorescence. In addition, the pathway of this one-pot reaction and the mechanism of POCl3 mediated 5-exo cyclization have been proposed by a combining experimental and computational study.

A regioselective [3 + 2] cycloaddition reaction of 2-benzylidene-1-indenones with functional olefins to access indanone-fused 2D/3D skeletons

The regioselective [3 + 2] cycloaddition reaction of 2-benzylidene-1-indenones with functional olefins was established with DABCO as a base under mild conditions. Using this approach, a series of diversely substituted indanone-fused cyclopentane polycycles with highly crowded multiple substituents were synthesized in high yields.

Construction of Alkylidene Fluorene Scaffolds Using Pd-Catalyzed Direct Arene/Alkene Coupling Strategy

A versatile synthetic method for the construction of alkylidene fluorenes and their heteroarene derivatives has been developed successfully by means of a Pd(II)-catalyzed direct C-H/C-H coupling of o-alkenyl biaryls. Use of the Pd(OAc)₂ catalyst under aerobic oxidation conditions gives rise to the corresponding alkylidene fluorenes having various functional groups and diversely fused polycyclic systems. The resulting products can serve as versatile synthetic building blocks for the construction of structurally diverse polycyclic arenes and heteroarenes.

Copper-Catalyzed 6-endo-dig Cyclization-Coupling of 2-Bromoaryl Ketones and Terminal Alkynes toward Naphthyl Aryl Ethers in Water

The cyclization-coupling reaction of 2-bromoaryl ketones and terminal alkynes is first realized by copper catalysis, which produces polyfunctional naphthyl aryl ethers in moderate to excellent yields with broad substrate scope and good functional group tolerance. This reaction proceeds via 6-endo-dig cyclization and C(sp²)-O coupling using green H₂O as the unique solvent and 5-bromopyrimidin-2-amine as the critical additive. Mechanistically, a unique Cu(III)-acetylide probably is the key intermediate, which allows exclusive 6-endo-dig selectivity.