Extending Aminations’ Reach

Two teams have independently developed reactions that convert boron-functionalized starting materials to amines without using transition-metal catalysts (J. Am. Chem. Soc., DOI: 10.1021/ja309637r and 10.1021/ja305448w). Alkyl- and arylamines are important reagents for pharmaceuticals and agrochemicals. Multiple transformations arrive at these amines, but they can require costly removal of metal contaminants or aren’t compatible with certain substrates. László Kürti of the University of Texas Southwestern Medical Center, Daniel H. Ess of Brigham Young University, and colleagues use O-(2,4-dinitrophenyl)­hydroxylamine to obtain multigram quantities of primary aromatic amines directly from aryl boronic acids. The team’s calculations suggest that the amination proceeds through an aryl migration mechanism. Meanwhile, James P. Morken of Boston College and coworkers combine methoxyamine and n-butyllithium to obtain amines from pinacol boronates. Pinacol boronates are more stable than many boron reagents but typically aren’t compatible with aminations. The Boston team’s reaction, in contrast, works with aryl and alkyl pinacol boronates. It proceeds at gram scales and retains stereochemistry at the carbon adjacent to the amine nitrogen.