Heuer Abigail M, Coste Scott C, Singh Gurjot, Mercado Brandon Q, Mayer James M
Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.
J Org Chem. 2023 Jul 21;88(14):9893-9901. doi: 10.1021/acs.joc.3c00658. Epub 2023 Jul 5.
Triphenylmethyl (trityl, PhC•) radicals have been considered the prototypical carbon-centered radical since their discovery in 1900. Tris(4-substituted)-trityls [(4-R-Ph)C•] have since been used in many ways due to their stability, persistence, and spectroscopic activity. Despite their widespread use, existing synthetic routes toward tris(4-substituted)-trityl radicals are not reproducible and often lead to impure materials. We report here robust syntheses of six electronically varied (4-RPh)C•, where R = NMe, OCH, Bu, Ph, Cl, and CF. The characterization reported for the radicals and related compounds includes five X-ray crystal structures, electrochemical potentials, and optical spectra. Each radical is best accessed using a stepwise approach from the trityl halide, (RPh)CCl or (RPh)CBr, by controllably removing the halide with subsequent 1e reduction of the trityl cation, (RPh)C. These syntheses afford consistently crystalline trityl radicals of high purity for further studies.
三苯甲基(三苯基,PhC•)自由基自1900年被发现以来,一直被视为典型的碳中心自由基。此后,三(4-取代)-三苯甲基自由基[(4-R-Ph)C•]因其稳定性、持久性和光谱活性而被广泛应用。尽管它们被广泛使用,但现有的合成三(4-取代)-三苯甲基自由基的路线不可重复,且常常导致产物不纯。我们在此报告了六种电子性质各异的(4-RPh)C•的可靠合成方法,其中R = NMe、OCH、Bu、Ph、Cl和CF。对这些自由基及相关化合物的表征包括五个X射线晶体结构、电化学电位和光谱。通过用三苯甲基阳离子(RPh)C进行后续的单电子还原可控地去除卤化物,从三苯甲基卤化物(RPh)CCl或(RPh)CBr采用逐步方法可最佳地获得每个自由基。这些合成方法可提供纯度高且始终为晶体的三苯甲基自由基,用于进一步研究。