Synlett 2015; 26(03): 345-349
DOI: 10.1055/s-0034-1379319
cluster
© Georg Thieme Verlag Stuttgart · New York

Copper-Catalyzed Aerobic C–H Trifluoromethylation of Phenanthrolines

Cheng-Liang Zhu
,
Yong-Qiang Zhang
,
Yong-An Yuan
,
Hao Xu*
Further Information

Publication History

Received: 01 September 2014

Accepted after revision: 22 September 2014

Publication Date:
21 October 2014 (online)

Abstract

Direct C–H trifluoromethylation of heterocycles is a valuable transformation. In particular, nonprecious metal-catalyzed C–H trifluoromethylation processes, which do not proceed through CF3 radical species, have been less developed. In this cluster report, a new copper-catalyzed aerobic C–H trifluoromethylation of phenanthrolines is described. This transformation affords trifluoromethylated phenanthrolines that have not been synthesized and preliminary mechanistic studies suggest that the CF3 group transfer may occur through cooperative activation.

Supporting Information

 
  • References and Notes

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  • 13 Typical Experimental Procedure To a mixture of 1,10-phenanthroline (1, 36 mg, 0.2 mmol), Cu(OAc)2 (7.4 mg, 0.04 mmol), KOAc (9.8 mg, 0.1 mmol), and AcOH (6.0 μL, 0.1 mmol) in toluene (4.0 mL), TMSCF3 (30 μL, 0.2 mmol) was added at room temperature under an O2 atmosphere. The reaction mixture was stirred at 40 °C for 3 h. Another portion of TMSCF3 (30 μL, 0.2 mmol) was added, and stirring was continued at 40 °C. The reaction was monitored by TLC. After the starting material was completely consumed, the reaction was quenched by H2O and extracted with EtOAc (3 × 4 mL). The combined organic layer was washed by brine, dried over Na2SO4, and concentrated in vacuo. The product 2 was isolated through a silica gel flash column (40% EtOAc in hexanes) as a white foam (41 mg, 80% yield). 2-(Trifluoromethyl)-1,10-phenanthroline (2) 1H NMR (400 MHz, CDCl3): δ = 9.24 (s, Ha), 8.38 (d, J = 8.4 Hz, Hf), 8.23 (d, J = 8.6 Hz, Hc), 7.93 (d, J = 8.4 Hz, Hg), 7.85, 7.78 (d, J = 8.8Hz, Hd and He), 7.65 (m, Hb) ppm. 13C NMR (100 MHz, CDCl3): δ = 151.06, 147.7 (q, J = 35.0 Hz), 145.72, 145.56, 137.83, 136.09, 129.76, 129.10, 128.79, 125.70, 123.59, 124.30 (q, J = 273 Hz), 119.00 ppm. 19F NMR (377 MHz, CDCl3): δ = 66.59 (s, 3 F) ppm. IR (neat): νmax = 3696, 2967, 2217, 1595, 1337, 1112, 851, 746 cm–1. ESI-HRMS: m/z calcd for C13H8N2F3 + [M + H+]: 249.0640; found: 249.0642.