Facile and Efficient SynthesisofFluorene and Indenoarene Carboxylates from Biaryldiazoacetates via BlueLight‐promoted Intramolecular CarbeneC−H Insertion. Issue 1 (19th December 2022)

• Record Type: Journal Article
• Authors: Zeng, Tong‐Tong; Zhang, Hao‐Yuan; Xie, Zhen‐Biao; Dong, Ying‐Ying; Gong, Shan‐Shan; Sun, Qi
• Is Part Of: Asian journal of organic chemistry. Volume 12:Issue 1(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-19
• Subjects: blue light -- fluorene -- photolysis -- carbene -- C−Hinsertion; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; 547.005
• DOI: 10.1002/ajoc.202200638
• Languages: English
• ISSNs: 2193-5807

Abstract

Abstract: Inspired by the recent discovery that aryldiazoacetates could be excited with visible light to generate carbenes in a mild and catalyst‐free manner, we tested the possibility to induce the cyclization of fluorenes from biaryldiazoacetate precursors simply by visible light irradiation at ambient temperature. The experimental results showed that 455 nm blue light is most effective on the synthesis of a diversity of fluorenes and indenoarenes in excellent yields. Analysis of UV absorbance and electronic transition properties of biaryldiazoacetates revealed that their absorbance peaks in the blue light region are due to the n–π* transition of diazo group. Their small ϵ 420 nm values well explains the fact that only when exposed to intense blue light could biaryldiazoaetates be excited to generate carbenes. Theoretical calculations and kinetic isotopic effect (KIE) study illustrated that the fluorene cyclization proceeds via the intramolecular carbene C−H insertion pathway rather than the cyclopropanation pathway. In addition, a furan ring‐opening mechanism for the unexpected formation of an indene‐based unsaturated aldehyde was also proposed based on the calculated potential energy surfaces of three plausible reaction pathways. Abstract : Simple irradiation of biaryldiazoacetates in CH2 Cl2 with 455 nm blue LED at ambient temperature afforded a diversity of fluorenes and indenoarenes with excellent yields in 30–55 min.Their specific absorbance in the blue light region has been proved as the result of n–π* transition of diazo group. Theoretical calculations reveal that the cyclization proceeds via the intramolecular carbene C−H insertion mechanism.