Sigmatropic Shifts Of N,O-Diaryl Hydroxylamine

N,O-Diarylhydroxylamines are a class of important intermediates in organic synthesis.Because their N-O bond strength is weak and easy to break,they favor to undergo various sigmatropic shift rearrangements after they are synthesized.In recent years,their [3,3] sigmatropic shift rearrangements have attracted more and more attention and applied in the preparation of2’-amino-[1,1’-binaphyl]-2-ols as ligands in catalytic reactions.In this dissertation,multisubstituted N-acylarylhydroxylamines and halobenzenes with ortho and para strong electron-withdrawing substituents were rationally designed and applied in the synthesis N,O-diarylhydroxylamines with special structural features through aromatic nucleophilic substitution reactions.The σ shift rearrangements of the generated N,O-diaryl hydroxylamines were realized in situ.The results indicate that N,O-diaryl hydroxylamines cannot undergo N[1,3] sigmatropic shift.The designed and synthesized N-acyl-N-(2,4,6-trisubstituted phenyl)-O-(4-substituted phenyl)hydroxylamines took place [3,3] σ shift rearrangement followed by nucleophilic addition to generate benzofuran derivatives,while N-acyl-N-(4-substituted phenyl)-O-(2,4,6-trisubstituted phenyl)hydroxylamines underwent O[1,3] σ shift rearrangement,and the products further underwent Smiles rearrangement,and amide/ester exchange reaction,affording 2-arylaminoaryl carboxylates.The reaction of N-acyl-N-arylhydroxylamines and halobenzenes with ortho and para strong electron-withdrawing substituents includes aromatic nucleophilic substitution,O [1,3] σ shift rearrangement,Smiles rearrangement,and amide/ester exchange four-type cascade reaction.N-acyl-N-phenyl-O-(2,4,6-trisubstituted phenyl)hydroxylamines favored double tandem O[1,3] σ shift rearrangement,giving formal O [1,5] σ shift products,4-aminodiaryl ethers.N-Acyl-N-(4-substituted phenyl)-O-(2,6-disubstituted phenyl)hydroxylamines underwent tandem O[1,3] and double tandem C[3,3] σ shift rearrangements,yielding formal [3,5]shift products,2-amino-[1,1’-biphenyl]-4-ols.Important organic compounds,such as benzofurans,2-arylaminoaryl carboxylates,2/4-aryloxyarenols,and 2-amino-[1,1’-biphenyl]-4-ols,were prepared in moderate to excellent yields through four different sigmatropic shift rearrangements of the rationally designed N,O-diarylhydroxylamines.The reactions feature easy operation,no inert gas protection,and mild reaction conditions.Arenesulfenanilides only undergo S[1,3] sigmatropic shift and double tandem S[1,3] sigmatropic shift rearrangements,while N,N’-diarylhydrazines can take place N[1,3],[3,3],[5,5],double tandem N[1,3] and tandem N[1,3]/[3,3] σ shift rearrangements.Similar as N,N’-diarylhydrazines,N,O-diarylhydroxylamines can also undergo various sigmatropic shifts,including O[1,3],[3,3],[5,5],double tandem O[1,3] and O[1,3]-double tandem C[3,3] σ shift rearrangements,rather than N[1,3] and double tandem N[1,3] σ shift rearrangements.Heteroatom σ shift rearrangements,the σ shift rearrangements of N,O-diarylhydroxylamines and their applications in organic synthesis were extended in this dissertation.