Photocatalyzed Borylcyclopropanation of Alkenes with a (Diborylmethyl)iodide Reagent
Jiefeng Hu1,2, Man Tang1, Jing Wang1
1School of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing, 211816 Jiangsu, China.
Abstract:
Cyclopropane skeletons play a prominent role in the development of organic synthesis and pharmaceutical chemistry. Herein, we report the design and synthesis of a stable, multifunctional (diborylmethyl)iodide reagent (CHI(Bpin)2 ) for the photoinduced cyclopropanation of alkenes, providing an array of 1,2-substituted cyclopropylboronates in good yields. This α-haloboronic ester can be readily synthesized on a multigram scale from commercially available starting materials. Furthermore, the protocol displays high chemo- and diastereoselectivity, excellent functional-group tolerance, and allows for late-stage borylcyclopropanation of complex molecules. Mechanistic studies reveal that the borylcyclopropanation proceeds through a radical addition/polar cyclization pathway mediated by the photocatalyst fac-Ir(ppy)3 and visible light.
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