Scheme 6. The [3+2] cycloaddition of cyclic nitrone with methyl propiolate.Figure 3. Rationalization of the high selectivity for the formation of 7 b. Angewandte Chemie 8949

N-CF 3 compounds constitute valuable targets in medicinal chemistry. Extensive studies have been reported for the preparation of N-CF 3 compounds through fluorination and trifluoromethylation of N-containing compounds. The development of new synthetic methods from abundant and easily available substrates is highly desirable but still challenging. Herein, we report the design and synthesis of novel N-Cbz-and N-Boc-Ntrifluoromethyl hydroxylamine reagents by silver-mediated oxidative trifluoromethylation. These reagents have been successfully applied to the direct incorporation of a NCF 3 moiety into the commonly used unsaturated substrates under photoredox catalysis. This protocol enables the efficient and regioselective C−H trifluoromethylamination of various (hetero)arenes, including complex bioactive molecules. Furthermore, a variety of alkenes, dienes, and isonitriles undergo tandem trifluoromethylamination/functionalization delivering structurally diverse N-trifluoromethyl aliphatic and heteroaromatic amines. Notably, previously unknown cyclic N-CF 3 compounds including N-CF 3 oxazolidinones and oxazolones were conveniently prepared with N-Boc-N-trifluoromethyl hydroxylamine reagents. Furthermore, diversification of the resulting α-trifluoromethylamino ketones afforded the largely underexplored N-alkenyl-and N-alkynyl-N-CF 3 compounds.

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The combination of AgTFA and Sc(OTf) enables the bimetallic synergistic catalysis of β-alkynyl ketones and para-quinone methides (p-QMs), allowing direct synthesis of 17 examples of benzo[c]xanthenes with generally good yields through a benzannulation/1,6-addition/cyclization sequence. Exchanging p-QMs for quinone imine ketal resulted in 10 examples of tetracyclic naphtho[1,2-b]benzofurans via a similar benzannulation/1,4-addition/cyclization cascade. During these reaction processes, AgTFA and Sc(OTf) could be perfectly compatible, together with the realization of C(sp)-H functionalization adjacent to carbonyl group on the β-alkynyl ketone unit.

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The direct synthesis of C(CF)Me-substituted heteroarenes by decarboxylative 1,1-dimethyltrifluoroethylation of heteroarenes with 3,3,3-trifluoro-2,2-dimethylpropanoic acid is reported. This method does not need the transition-metal catalyst, and the base is crucial for this reaction. A series of previously unknown C(CF)Me-containing heteroarenes were obtained in high yields and have potential applications in the drug discovery process.