Synthesis of trifluoromethyl alkanes
Sodium trifluoromethanesulfinate and iodine pentoxide as safe solid reagents enable a scalable, selective, and convenient iodotrifluoromethylation of a wide range of alkenes and alkynes in aqueous medium. Mechanistic studies confirm a free-radical processes, in which key radical intermediates such as CF3 and β-CF3 alkyl radicals have been detected by spin trapping and electron spin resonance.
Z. Hang, Z. Li, Z.-Q. Liu, Org. Lett., 2014, 16, 3648-3651.
In a photoredox vicinal chlorotrifluoromethylation in the presence of Ru(Phen)3Cl2 as catalyst, various terminal and internal alkenes can be transformed to their vicinal chlorotrifluoromethylated derivatives using CF3SO2Cl as a source for CF3 radicals and chloride ions.
S. H. Oh, Y. R. Malpani, N. Ha, Y.-S. Jung, S. B. Han, Org. Lett., 2014, 16, 1310-1313.
The use of NaSO2CF3 and NaBrO3 enables a free-radical bromotrifluoromethylation of olefins via a radical process. Sodium bromate acts not only as a single-electron oxidant but also as a bromine source.
Z.-Q. Liu, D. Liu, J. Org. Chem., 2017, 82, 1649-1656.
2,4,6-Trimethylpyridine catalyzes a trifluoromethylalkynylation of unactivated alkenes with alkynyl sulfones and Togni's reagent to provide various β-trifluoromethylated alkynes under metal-free conditions with a broad substrate scope and wide functional group compatibility. A mechanism involving catalytic nonchain radical processes is proposed.
S. Zhou, T. Song, H. Chen, Z. Liu, H. Shen, C. Li, Org. Lett., 2017, 19, 698-701.
A copper-catalyzed intermolecular cyanotrifluoromethylation of alkenes provides various CF3-containing alkylnitriles with excellent enantiomeric excess. The reaction is initiated by a SET process between activated Togni’s CF3+ reagent and a Cu(I) catalyst. The released CF3 radical readily added to styrene to provide a benzylic radical, which is then trapped by a chiral Cu(II) cyanide species.
F. Wang, D. Wang, X. Wan, L. Wu, P. Chen, G. Liu, J. Am. Chem. Soc., 2016, 138, 15547-15550.
A highly practical copper-catalyzed intermolecular cyanotrifluoromethylation of alkenes provides a general and straightforward way to synthesize various useful CF3-containing nitriles, which can be used for the preparation of pharmaceutically and agrochemically important compounds.
Y.-T. He, L.-H. Li, Y.-F. Yang, Z.-Z. Zhou, H.-L. Hua, X.-Y. Liu, Y.-M. Liang, Org. Lett., 2014, 16, 270-273.
A highly regioselective cyanotrifluoromethylation of electron-deficient styrenes with a trifluoromethylated hypervalent iodine reagent proceeds under mild conditions in the presence of a bulky phosphine and CuCN. The process involves the consecutive formation of two C-C bonds in a single addition reaction. In the presence of a p-methoxy substituent in the styrene, oxytrifluoromethylation occurs instead of the cyanotrifluoromethylation.
N. O. Ilchenko, P. G. Janson, K. J. Szabó, J. Org. Chem., 2013, 78, 11087-11091.
A photoredox-catalyzed azidotrifluoromethylation of substituted styrenes as well as various activated and nonactivated alkenes using [Ru(bpy)3(PF6)2] as the photocatalyst and Umemoto’s reagent as the CF3 source delivers a wide range β-trifluoromethylated azides or amines in good yields.
G. Dagousset, A. Carboni, E. Magnier, G. Masson, Org. Lett., 2014, 16, 4340-4343.