Method C. Solutions were prepared by sequential addition of 2.5 X lo-'mol quantities of pyridine 1-oxide, trimethylsilanecarbonitrile, and acylating agent to 0.4 mL of chloroform-d that contained 1% tetramethylsilane. The final solutions were approximately 0.5 M in each reactant. NMR tubes with screwcaps and Teflon liners (Wilmad No. 507-TR) were used as reaction vessels.