Brønsted acid-catalyzed homogeneous O–H and S–H insertion reactions under metal- and ligand-free conditions

Abstract

The economical and accessible CF3SO3H successfully catalyzed homogeneous O–H and S–H bond insertion reactions between hydroxyl compounds, thiols and diazo compounds under metal- and ligand-free conditions.

Chemodivergent Synthesis of Oxazoles and Oxime Ethers Initiated by Selective C–N/C–O Formation of Oximes and Diazo Esters

“…Considering the excellent electrophilic properties of carbene species, we envisioned an alternative approach to nitrones through possible C–N bond formation and 1,3-proton transfer or an intermolecular proton transfer starting from oximes and α-diazoesters, the latter of which may play the role of latent carbene precursors (Scheme c) . On the contrary, a Rh-catalyzed [3+2] annulation and a photodriven O–H insertion of oximes were found instead of the aforementioned transformation, providing biologically active oxazoles and oxime ethers in a controllable manner. − Here, we report the catalyst-dependent chemodivergent reactions.…”

Recent Advances in the Total Synthesis of Cephalotane-Type Norditerpenoids from Cephalotaxus sinensis

“…In the following year, an asymmetric total synthesis of cephanolide B was reported by Gao. 31b As shown in Scheme 7 , the ester side chain was introduced starting from the known substituted ketone 78 via a Pd-catalyzed coupling. This was followed by carrying out a 1,2-addition under the action of CuBr·Me 2 S to obtain the adduct 80 .…”

Solvent‐free, B(C6F5)3‐Catalyzed S−H Insertion of Thiophenols and Thiols with α‐Diazoesters

“…However, metal‐free approaches are still under developing (Scheme 1c) [14] . Quite recently, urea‐, visible light‐ and Brønsted acid‐catalyzed versions have been reported by the groups of Mattson (2014), [14a] Qiu and Guo (2020), [14b] Yang and Huo (2020), [14c] and Huang (2021) [14d] (Scheme 1c). Driven by the significant importance of the synthesis of these sulphur‐containing motifs and the meaningful organoborane catalysis research, we initiated the research project of the borane‐catalyzed S−H insertion with α‐diazoesters, which cultivated a solvent‐free protocol of this transformation presented herein (Scheme 1d).…”