Репост из: JACS ASAP
Photo-Stitching of Nitroalkanes via Cross-Denitrative Olefination
Joshua K. Mitchell, Shrey P. Desai, Joseph M. Bergen, Alexandria Reyes, Maxwell S. McLean, Poulami Ghosh, Ajay H. Bansode, Marvin Parasram*
Abstract: Despite their centrality in molecular design, stereodefined tri- and tetrasubstituted alkenes remain challenging to access, as most olefinations favor lower substitution and fail under sterically congested settings. Herein, we report the photoinduced cross-denitrative olefination of nitroalkanes to afford tri- and tetrasubstituted alkenes. Visible light excitation of in situ–generated nitronates promotes a photo-stitching event via denitrative cross-coupling of two nitroalkanes. The transformation tolerates a variety of functionalized nitroalkanes, including carbonyl- and heterocycle-containing substrates, complements metathesis and carbonyl olefination, and scales efficiently. Mechanistic studies support a photoinitiated and photopropagated nucleophilic-radical substitution and radical-chain elimination sequence in which nitronates function as photoreductants to generate radical-anion intermediates that undergo a subsequent photodriven β-elimination. These findings establish a previously inaccessible light-driven elimination process for radical-mediated olefination from readily available building blocks.
❯ Link to the article
Joshua K. Mitchell, Shrey P. Desai, Joseph M. Bergen, Alexandria Reyes, Maxwell S. McLean, Poulami Ghosh, Ajay H. Bansode, Marvin Parasram*
Abstract: Despite their centrality in molecular design, stereodefined tri- and tetrasubstituted alkenes remain challenging to access, as most olefinations favor lower substitution and fail under sterically congested settings. Herein, we report the photoinduced cross-denitrative olefination of nitroalkanes to afford tri- and tetrasubstituted alkenes. Visible light excitation of in situ–generated nitronates promotes a photo-stitching event via denitrative cross-coupling of two nitroalkanes. The transformation tolerates a variety of functionalized nitroalkanes, including carbonyl- and heterocycle-containing substrates, complements metathesis and carbonyl olefination, and scales efficiently. Mechanistic studies support a photoinitiated and photopropagated nucleophilic-radical substitution and radical-chain elimination sequence in which nitronates function as photoreductants to generate radical-anion intermediates that undergo a subsequent photodriven β-elimination. These findings establish a previously inaccessible light-driven elimination process for radical-mediated olefination from readily available building blocks.
❯ Link to the article