Catalyst-Assisted Selective Vinylation and Methylallylation of a Quaternary Carbon Center Using tert-Butyl Acetate

The In-(OTf)(3)-catalyzed & alpha;-vinylationof varioushydroxy-functionalized quaternary carbon centers using in situ generatedisobutylene from tert-butyl acetate is presentedas a novel synthetic methodology. Moreover, tert-butylacetate is a nonflammable feed stock and is a readily available sourcefor the in situ production of vinyl substituents, as demonstratedby the vinylation reaction with quaternary hydroxy/methoxy compounds.Moreover, an excellent selectivity for methylallylation over vinylationwas obtained with Ni-(OTf)(2) as a catalyst. In the case ofperoxyoxindole, methylallyl-functionalized 1,4-benzoxazin-3-one derivativeswere formed through the sequential rearrangement of peroxyoxindolefollowed by the nucleophilic attack by isobutylene. The detailed mechanismfor this reaction and rationalization for the selectivity are providedusing kinetics and density functional theory studies.

Automated summary

This study introduces a new synthetic methodology using In-(OTf)(3)-catalyzed α-vinylation of various hydroxy-functionalized quaternary carbon centers with in situ generated isobutylene from tert-butyl acetate. It demonstrates that tert-butyl acetate is a nonflammable feedstock and a readily available source for in situ production of vinyl substituents. Furthermore, Ni-(OTf)(2) shows excellent selectivity for methylallylation over vinylation as a catalyst. The sequential rearrangement of peroxyoxindole followed by nucleophilic attack by isobutylene leads to the formation of methylallyl-functionalized 1,4-benzoxazin-3-one derivatives. The reaction mechanism and selectivity are explained using kinetics and density functional theory studies.