Visible‐Light‐Driven Strain‐Increase Ring Contraction Allows the Synthesis of Cyclobutyl Boronic Esters

Davenport, Raffael; Silvi, Mattia; Noble, Adam; Hosni, Zied; Fey, Natalie; Aggarwal, Varinder K.

Abstract

There are a limited number of ring‐contraction methodologies which convert readily available five‐membered rings into strained four‐membered rings. Here we report a photo‐induced radical‐mediated ring contraction of five‐membered‐ring alkenyl boronate complexes into cyclobutanes. The process involves the addition of an electrophilic radical to the electron‐rich alkenyl boronate complex, leading to an α‐boryl radical. Upon one‐electron oxidation, ring‐contractive 1,2‐metalate rearrangement occurs to give a cyclobutyl boronic ester. A range of radical precursors and vinyl boronates can be employed, and chiral cyclobutanes can be accessed with high levels of stereocontrol. The process was extended to the preparation of benzofused cyclobutenes and the versatility of the boronic ester was demonstrated by conversion to other functional groups.

Citation

Davenport, R., Silvi, M., Noble, A., Hosni, Z., Fey, N., & Aggarwal, V. K. (2020). Visible‐Light‐Driven Strain‐Increase Ring Contraction Allows the Synthesis of Cyclobutyl Boronic Esters. Angewandte Chemie International Edition, 59(16), 6525-6528. https://doi.org/10.1002/anie.201915409

• Journal Article Type: Article
• Acceptance Date: Jan 8, 2020
• Online Publication Date: Jan 8, 2020
• Publication Date: Apr 16, 2020
• Deposit Date: May 7, 2020
• Publicly Available Date: Jan 9, 2021
• Print ISSN: 1433-7851
• Electronic ISSN: 1521-3773
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 59
• Issue: 16
• Pages: 6525-6528
• DOI: https://doi.org/10.1002/anie.201915409
• Keywords: Photoredox catalysis; Boron chemistry ; Ring contraction ; Metalate rearrangement; Cyclobutanes
• Public URL: https://nottingham-repository.worktribe.com/output/4176434
• Publisher URL: https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201915409
• Additional Information: This is the peer reviewed version of the following article: Visible‐Light‐Driven Strain‐Increase Ring Contraction Allows the Synthesis of Cyclobutyl Boronic Esters Dr. Raffael Davenport Dr. Mattia Silvi Dr. Adam Noble Dr. Zied Hosni Dr. Natalie Fey Prof. Dr. Varinder K. Aggarwal Angew. Chem. Int. Ed. 2020, 59, 6525, which has been published in final form at https://doi.org/10.1002/anie.201915409. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.