Catalytic Generation of Radicals from Nitroalkanes

Myuto Kashihara; Kohei Kosaka; Naoki Matsushita; Shunta Notsu; Ayumi Osawa; Yoshiaki Nakao

doi:10.1055/a-1942-0683

Synlett, Inhaltsverzeichnis

Synlett 2023; 34(12): 1482-1486
DOI: 10.1055/a-1942-0683

cluster

Special Issue Honoring Masahiro Murakami’s Contributions to Science

Catalytic Generation of Radicals from Nitroalkanes

Myuto Kashihara

,

Kohei Kosaka‡

,

Naoki Matsushita‡

,

Shunta Notsu

,

Ayumi Osawa

,

Yoshiaki Nakao∗

Abstract

Alle Artikel dieser Rubrik

This paper is dedicated to Professor Masahiro Murakami on the occasion of his retirement.

Abstract

A new protocol for the catalytic denitrative generation of radicals from nitroalkanes was disclosed. 9-Fluorenol acts as a single-electron transfer catalyst that reduces nitroalkanes to promote the C-NO₂ bond cleavage, followed by the formation of alkyl radicals. The obtained radicals participate in diverse transformations such as hydrogenation, Giese addition, spirocyclization, and Minisci reactions by using appropriate trapping reagents. The present system outperforms conventional methods using tin hydrides in terms of cost, toxicity, and experimental operations.

Key words

nitroalkane - 9-fluorenol - single-electron transfer - denitration - radical - organocatalysis

Volltext

Referenzen

References and Notes
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29 Typical Procedure for the Denitrative Radical Transformation of Nitroalkanes A 15-mL vial equipped with a magnetic stirrer bar was charged with nitroalkane 1 (0.60 mmol), radical acceptor 2, 6, 8, or 10 (0.60–1.8 mmol), K₃PO₄ (0.90–1.8 mmol), and 2-propanol (3.0–6.0 mL) under a nitrogen atmosphere. The resulting mixture was stirred at 110 °C. After completion of the reaction, the mixture was filtered through a short pad of Celite^® and eluted with EtOAc. All volatiles were removed in vacuo, and the residue was purified by a silica gel column chromatography. Analytical Data for 4l ¹H NMR (400 MHz, acetone-d ₆): δ = 7.36–7.19 (m, 5 H), 2.99 (dd, J = 14.2, 5.0 Hz, 1 H), 2.70 (dd, J = 14.0, 8.9 Hz, 1 H), 2.59–2.42 (m, 1 H), 1.65–1.45 (m, 2 H), 0.93 (td, J = 7.6, 0.9 Hz, 3 H). ¹³C NMR (101 MHz, CDCl₃): δ = 138.6, 129.0, 128.5, 128.4 (q, J = 280.8 Hz), 126.5, 45.9 (q, J = 24.0 Hz), 33.7, 20.3, 11.2. ¹⁹F NMR (376 MHz, CDCl₃): δ = –70.1. HRMS (EI) (+): m/z [M]⁺ calcd for C₁₁H₁₃F₃: 202.0969; found: 202.0963. Analytical Data for 9e ¹H NMR (400 MHz, acetone-d ₆): δ = 7.39–7.33 (m, 2 H), 7.27–7.20 (m, 3 H), 7.11 (d, J = 10.2 Hz, 2 H), 6.46 (s, 1 H), 6.19 (d, J = 10.1 Hz, 2 H), 2.16 (s, 2 H), 1.74–1.58 (m, 6 H), 1.57–1.36 (m, 4 H). ¹³C NMR (101 MHz, CDCl₃): δ = 185.9, 156.4, 140.7, 140.6, 135.3, 128.3, 127.9, 127.8, 125.9, 56.0, 48.7, 48.6, 38.8, 25.6, 23.3. ESI-HRMS (+): m/z [M + Na]⁺ calcd for C₂₁H₂₂ONa: 313.1563; found: 313.1561. Experimental details and analytical data for other compounds are provided in the Supporting Information.

Zusatzmaterial

Supporting Information