Two Unprecedented Reactions of Nitrosyl Triflate: NO+-Induced Cationic Cascade Cyclization and C═C Oxidative Cleavage

Direct Aromatic Nitrosation Using 2-Methoxyethyl Nitrite as a NO Cation Source

This work presents an acid-free method for aromatic nitrosation using 2-methoxyethyl nitrite (MOE-ONO). While originally developed as a NOx radical source in our group, we demonstrate the utility of MOE-ONO as a NO cation source for aromatic electrophilic nitrosation. This method successfully nitrosates phenols, naphthols, and other pronucleophiles, completely suppressing undesired nitration by NOx radicals. Notably, it enables nitrosation of acid-sensitive substrates, which has been difficult to achieve with existing protocols.

Specific and Strong Acceleration of Nitrosation by Nitrosyl Sulfonates Using the Bis-Coordinating Lewis Acid TiCl4 or SnCl4

Nitrosyl triflate is an excellent donor of NO+ to C═C and very unreactive benzenoids, in contrast to the much less reactive nitrosyl mesylate. However, both of these reagents are strongly activated by the bis-coordinating Lewis acids TiCl4 and SnCl4 and become super reactive NO+ donors. Strong catalysis and activation are even observed with the inherently less electrophilic nitrosyl trifluoroacetate. Monocoordinating strong Lewis acids, e.g., MeAlCl2, are relatively ineffective.

Synthetically Useful Transformations of Olefins via Cationic 1,2-Oxazetium Intermediates

Nitrosyl triflate serves as a NO+ donor in reactions with many olefinic substrates to form reactive, cationic 1,2-oxazetium cycloadducts that can be converted selectively into a wide range of useful products depending on reagents and conditions.