1. Migratory functionalization of unactivated alkyl bromides for construction of all-carbon quaternary centers via transposed tert-C-radicals
- Author
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Ze-Yao Liu, Heng Zhang, Luning Tang, Chao Feng, Chuan Zhu, Yu-Feng Zhang, and Patrick J. Walsh
- Subjects
Steric effects ,Radical ,Science ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,General Biochemistry, Genetics and Molecular Biology ,Article ,Catalysis ,lcsh:Science ,Alkyl ,chemistry.chemical_classification ,Multidisciplinary ,Primary (chemistry) ,010405 organic chemistry ,Catalytic mechanisms ,General Chemistry ,Homogeneous catalysis ,0104 chemical sciences ,Homolysis ,Chemistry ,chemistry ,Reagent ,Chain walking ,lcsh:Q ,Isomerization - Abstract
Despite remarkable recent advances in transition-metal-catalyzed C(sp3)−C cross-coupling reactions, there remain challenging bond formations. One class of such reactions include the formation of tertiary-C(sp3)−C bonds, presumably due to unfavorable steric interactions and competing isomerizations of tertiary alkyl metal intermediates. Reported herein is a Ni-catalyzed migratory 3,3-difluoroallylation of unactivated alkyl bromides at remote tertiary centers. This approach enables the facile construction of otherwise difficult to prepare all-carbon quaternary centers. Key to the success of this transformation is an unusual remote functionalization via chain walking to the most sterically hindered tertiary C(sp3) center of the substrate. Preliminary mechanistic and radical trapping studies with primary alkyl bromides suggest a unique mode of tertiary C-radical generation through chain-walking followed by Ni–C bond homolysis. This strategy is complementary to the existing coupling protocols with tert-alkyl organometallic or -alkyl halide reagents, and it enables the expedient formation of quaternary centers from easily available starting materials., Formation of tertiary C(sp3)-C bonds is a formidable challenge due to steric interactions and low barriers for isomerization of intermediates. Here, the authors show a Ni-catalyzed migratory 3,3-difluoroallylation of unactivated alkyl bromides at remote tertiary carbon centers.
- Published
- 2020
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