RESUMEN
ß-Acetoxy alcohols can be synthesized in good yields with excellent diastereoselectivity from tertiary alcohols through PhI(OAc)2-mediated metal-free ß-acetoxylation. Mechanistic studies showed that the ß-acetoxylation process might undergo dehydration and sequential highly regioselective and diastereoseletive dioxygenation. Gram scale and diverse useful scaffolds could be prepared via this ß-acetoxylation process.
RESUMEN
An efficient transition-metal-free method for the preparation of α,ß-unsaturated N-aryl ketonitrones under mild conditions has been developed. This reaction shows good functional group tolerance for both electron-rich and electron-deficient substituents on both oximes and diaryliodonium salts. Two examples of gram-scale preparations have been realized in good yields. Further transformations of these nitrones to different N-heterocycles have been demonstrated. DFT calculations suggest that N-arylation products are formed by [1,3]-phenyl migration of an O-coordinated oximate complex via a four-centered transition state, while the O-arylation products are formed by [1,3]-phenyl migration of a N-coordinated oximate complex.
RESUMEN
Various benzoxazonines were synthesized through a formal [7 + 2] cycloaddition of arynes with N-vinyl-α,ß-unsaturated nitrones under mild conditions. Controllable N-O bond cleavage of benzoxazonines afforded polysubstituted pyrrole-tethered benzopyrans and acyclic ketone-substituted phenols in moderate to good yields. Further transformations provided a facile approach to access useful building blocks with specific stereoselectivity.