Synthesis of Functionalized 4-Hydroxy Carbazoles and Carbazole Alkaloids via Ring Expansion of Indole Cyclopentanone

The exploration of a ring expansion reaction from indole cyclopentanone to generate a range of diversely functionalized 4-hydroxyl carbazole frameworks, representing the core structure of numerous carbazole alkaloids, has been conducted under mild reaction conditions. This approach exhibits broad functional group tolerance and moderate to good yields. The practical applicability of this strategy has been demonstrated through the concise syntheses of carbazomycins A, D, and G.

Intramolecular One-Carbon Homologation of Unstrained Ketones via C-C Activation-Enabled 1,1-Insertion of Alkenes

Here, we describe the development of a Rh-catalyzed intramolecular one-carbon homologation of unstrained aryl ketones through a formal 1,1-insertion process of olefins, enabled by temporary directing group (TDG)-aided C-C activation. The reaction provides a distinct approach to access various substituted 1-indanones. Computational mechanistic studies reveal that the formal 1,1-insertion is realized by a selective C(sp²)-C(sp³) activation and turnover limiting 2,1-insertion into the alkene, followed by a facile β-H elimination and reinsertion process.

Ring Expansion of 1-Indanones to 2-Halo-1-naphthols as an Entry Point to Gilvocarcin Natural Products

Herein, we describe a two-step ring expansion of 1-indanones to afford 2-chloro/bromo-1-naphthols (32 examples). The developed method shows broad functional group tolerance, benefits from mild reaction conditions, and enables rapid access to the tetracyclic core of gilvocarcin natural products. The orthogonally functionalized products allow for selective postmodifications as exemplified in the total synthesis of defucogilvocarcin M. For the selective oxidation of the chromene, a mild and regioselective oxidation protocol (DDQ and TBHP) was developed.

Copper-Catalyzed Ring-Opening Defluorinative Alkylation of Siloxydifluorocyclopropanes: Synthesis of γ-Fluoro-δ-Ketoesters and γ,δ-Diketonitriles

In view of the importance of both fluorinated synthons and homoenolate equivalents, synthetic application of difluorocyclopropanols is desired but remains challenging due to their thermodynamic instability. Herein, we use siloxydifluorocyclopropanes as difluorocyclopropanol precursors to carry out new Cu-catalyzed ring-opening defluorinative alkylation. With α-bromo carboxylic esters as coupling partners, the reaction affords γ-fluoro-δ-ketoesters via a Cu^I/Cu^II catalytic cycle. Interestingly, by the use of α-bromoamides, the ring-opening defluorinative alkylation is followed by an additional intramolecular C-N oxidative coupling to deliver a lactam intermediate, which further undergoes defluorination, hydrolysis, ring opening, and dehydration cascade via a Cu^I/Cu^II/Cu^III catalytic pathway, leading to γ,δ-diketonitriles as the final products.

China's flourishing synthetic organofluorine chemistry: innovations in the new millennium

The new millennium has witnessed the rapid development of synthetic organofluorine chemistry all over the world, and chemists in China have made significant contributions in this field. This review aims to provide a brief introduction to China's primary innovations from 2000 to early 2017, covering fluorination, fluoroalkylation, fluoromethylthiolation, fluoroolefination and polyfluoroarylation, as well as synthesis with fluorinated building blocks. Recent advances in the chemistry of difluorocarbene and the chemistry of carbon–fluorine bond activation are also discussed. As a conclusion, the review ends with some personal perspectives on the future development of China's synthetic organofluorine chemistry.

The iso-Nazarov reaction

The acid-promoted cycloisomerization of conjugated dienals and linearly-conjugated dienones for the synthesis of five-membered ring systems is reviewed.

Rapid Access to Orthogonally Functionalized Naphthalenes: Application to the Total Synthesis of the Anticancer Agent Chartarin

We report the synthesis of orthogonally functionalized naphthalenes from simple, commercially available indanones in four steps. The developed method proceeds through a two-step process that features a thermally induced fragmentation of a cyclopropane indanone with simultaneous 1,2-chloride shift. Migration of the chloride substituent occurs in a regioselective manner to preferentially afford the para-chloronaphthol substitution pattern. The obtained naphthols are versatile building blocks that can be selectively modified and used for the efficient construction of biologically active molecules. This has enabled the total synthesis of the potent anticancer natural product chartarin through a highly convergent retrosynthetic bond disconnection.