Specific and Strong Acceleration of Nitrosation by Nitrosyl Sulfonates Using the Bis-Coordinating Lewis Acid TiCl 4 or SnCl 4 .

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 TiCl 4 and SnCl 4 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., MeAlCl 2 , are relatively ineffective.