Light-driven Synthesis Of 6-trifluoromethyl-phenanthridines

Phenanthridine is a common structural unit widely found in various natural alkaloids.In particular,6-trifluoromethyl-phenanthridines have a special chemical and biological activity because they contain a trifluoromethyl group,and are widely used in functional materials,biology,and pharmaceutical fields.Therefore,the synthesis of 6-trifluoromethyl-phenanthridine derivatives has received continuous attention from organic synthesis workers.Light energy,as a kind of clean energy source,has proven effective in photocatalytic organic transformations,making this process more simple and environment-friendly.In this context,it is of great importance to develop light-driven synthetic methods of 6-trifluoromethylphenanthridines.Based on extensive literature review and preliminary experimental results,a series of experiments for the synthesis of light-promoted 6-trifluoromethyl-phenanthridine derivatives have been conducted in this paper.And the details are as follows:An external oxidant-free method for the synthesis of 6-trifluoromethyl-phenanthridines has been developed.6-trifluoromethyl-phenanthridines were obtained from 2-aryl phenyl isocyanides and Langlois' reagent via a tandem light-driven trifluromethylation and an intermolecular radical annulation.The optimal reaction conditions were obtained through the screening of light sources,reaction time,solvent,addtives and etc.With this optimal reaction conditions,the functional group tolerance and the reaction efficiency were further examined,delivering a variety of 6-trifluoromethyl-phenanthridines.Moreover,a putative mechanism was proposed based on the previous works and the results of control experiments.A practical protocol for the synthesis of diverse 6-trifluoromethyl-phenanthridines from 2-aryl phenyl isocyanides and Langlois' reagent via visible-light-induced tandem radical addition-cyclization has been developed,in which the hydrazone-based 2D-COF-1 was employed as the heterogeneous photosensitizer.Under the blue LED irradiation,the reactions performed well,delivering multifarious 6-substituted phenanthridines in high yields.Benefited from the utilization of heterogeneous photocatalyst,this protocol features easy catalyst separation and excellent recyclability.It provides a new route for the visible light to promote the synthesis of 6-trifluoromethylphenanthridines.