Binary-Acid Catalysis with Sc(OTf)3/TfOH in the Alkenylation of Arenes with Alkynes

Photoactive Arylamine Appended β-Naphthols via Friedel-Crafts Alkylation of Vinylidine Quinone Methides (VQMs)

Substituted naphthol derivatives have received significant attention due to their wide range of biological and pharmaceutical activities, and further extending the generation of naphthol with photoactive materials promotes optoelectronic applications. Nevertheless, the synthetic methodology of such materials hitherto unknown. In this study, we have adopted an efficient Friedel-Crafts reaction of ortho-alkynylnaphthols with N,N-disubstituted arylamines to generate arylamine-appended β-naphthol derivatives. This transformation features broad substrate scope, excellent yields, and high atom economy and the method was successfully adapted for late-stage functionalization of biomolecules and drug molecules with excellent yields. Further, UV-vis absorption and emission studies reveal that these materials have shown visible range absorption and blue emission with a quantum efficiency of 10%. Lately, photo-irradiation on arylamine leads to a charged state that facilitates the improvement of the electronic properties. Consequently, novel synthetic methodology of photoactive materials paves the way to generate new developments in the area of small molecule-derived optoelectronics.

Organocatalytic Synthesis of Furan-Embedded Styrene Atropisomers

Herein, we report the first synthesis of furan-embedded styrene atropisomers via the reaction between 1-(aryl-ethynyl)-naphthalen-2-ol and γ-hydroxyenone. The reaction proceeds through in situ furan formation from γ-hydroxyenone. The styrene derivatives were obtained in moderate to good yields with high diastereoselectivities with a catalytic amount of PTSA. Few applications such as triazole formation and cross-coupling reactions have been demonstrated. A preliminary catalytic asymmetric version was also reported.

Divergent Coupling of ortho-Alkynylnaphthols and Benzofurans: [4 + 2] Cycloaddition and Friedel-Crafts Reaction

Catalytic direct [4 + 2] cycloaddition reactions and Friedel-Crafts reactions of ortho-alkynylnaphthols with benzofurans have been developed, affording functionalized hydrobenzofuro[3,2-b]chromans and hydroarylation products, respectively, in high yields with high chemoselectivity.

Vinyl cation-mediated intramolecular hydroarylation of alkynes using pyridinium reagents

Once considered to be exotic species of limited synthetic utility, vinyl cations have recently been shown to be highly versatile intermediates in a variety of processes. Here, we report a method for the synthesis of aryl-substituted benzocycloheptenes and -hexenes using the hydrotriflate salt of an electron-poor pyridine as a uniquely efficient proton source for a vinyl cation mediated Friedel-Crafts cyclization. The mild conditions made possible by this reagent allowed a range of simple and functionalized alkynes bearing pendant aryl groups to serve as suitable substrates for this scalable and convenient protocol.

Enantioselective Friedel-Crafts Reaction of 2-Alkynyphenols with Aromatic Ethers by Chiral Brønsted Acid Catalysis

Herein, we report chiral strong Brønsted acid-catalyzed enantioselective Friedel-Crafts reaction of 2-alkynyphenols with aromatic ethers. The reaction affords the corresponding axially chiral styrenes in up to 91% yield and 97% ee.