郑州大学牛林彬团队报道了双光氧化还原/钴催化异偶联两个相似的苄基自由基。相关研究成果发表在2024年12月24日出版的《德国应用化学》。

过渡金属调节的自由基交叉偶联，使两个不同的瞬态自由基能够选择性结合，而用于分选两个几乎相同的瞬态自由基团，特别是相似的苄基自由基的催化方法仍然很少见。

该文中，研究表明利用双光氧化还原/钴催化，可以选择性地偶联两个相似的苄基。研究人员使用易于获得的甲基芳烃和苯乙酸酯（苄基N-羟基邻苯二甲酰亚胺（NHPI）酯），作为苄基自由基来源，通过1°-1°、1°-2°、1℃-3°、2°-2°，2°-3°和3°-3°偶联，获得了一系列不对称的1,2-二芳基乙烷类，具有广泛的官能团耐受性。

除了光化学连续流合成外，直接使用苯乙酸和NHPI作为起始原料，以避免预先制备用于克级合成的苄基NHPI酯的一锅法也是可行的，并且产率很高，并展示了该方案的合成实用性。

附：英文原文

Title: Heterocoupling Two Similar Benzyl Radicals by Dual Photoredox/Cobalt Catalysis

Author: Wei Yang, Zhenyan Zhao, Yu Lan, Zhou Dong, Ruiying Chang, Yihang Bai, Shihan Liu, Shi-Jun Li, Linbin Niu

Issue&Volume: 2024-12-24

Abstract: Transition-metal-regulated radical cross coupling enables the selective bonding of two distinct transient radicals, whereas the catalytic method for sorting two almost identical transient radicals, especially similar benzyl radicals, is still rare. Herein, we show that leveraging dual photoredox/cobalt catalysis can selectively couple two similar benzyl radicals. Using easily accessible methylarenes and phenylacetates (benzyl N-hydroxyphthalimide (NHPI) esters) as benzyl radical sources, a range of unsymmetrical 1,2-diarylethane classes via the 1°–1°, 1°–2°, 1°–3°, 2°–2°, 2°–3° and 3°–3° couplings were obtained with broad functional group tolerance. Besides the photochemical continuous flow synthesis, the one-pot procedure that directly uses phenylacetic acids and NHPI as the starting materials to avoid the pre-preparation of benzyl NHPI esters for the gram-scale synthesis is also feasible and affords good yields, showcasing the synthetic utility of our protocol.

DOI: 10.1002/anie.202421256

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202421256