Chemoselective Nitrosylation of Anilines and Alkynes via Fragmentary or Complete NO Incorporation

The cycloaddition reactions have been explored extensively and provided an efficient strategy for the synthesis of cyclic compounds. Traditionally, the reaction partners were in extenso incorporated into the cyclic products without fragmentation. From a different perspective, if certain fragmentations via chemical-bond cleavage are involved in this cycloaddition reaction, it would change the assembly sequence and enable more product diversity. Here, we report a chemoselective nitrosylation of anilines and alkynes through fragmentary or complete NO radical incorporation. The formation of multiple C-N bonds, an unexpected C-N bond, and N=O bond cleavage make this fragmentary cycloaddition reaction an efficient approach to 2,5-dihydrooxazoles, 1H-1,2,3-triazole 2-oxides or quinoxaline N-oxides. Facile operation in open-air, metal-free, and mild conditions renders this protocol particularly practical and attractive. A series of mechanistic studies and density functional theory calculations were also conducted, which help to explain the fragmentary or complete NO incorporation processes, broadening the field of new reaction discovery.