Lead tetra-acetate-mediated oxidative cyclizations of isoquinoline alkyl substituted methylene urethanes (enamides) to isoquinoline hydroxyoxazolidinones

Abstract

Oxidation of disubstituted 1-methylene-tetrahydroisoquinoline-2-carboxylates with lead tetra-acetate (LTA) causes a rapid oxidative cyclization to an isoquinoline hydroxyoxazolidinone. The products possess acyliminium character and the hydroxy group is readily replaced by alcohol or reduced by hydride. Cleavage of the reduced hydroxyoxazolidinone by base leads to the tertiary β-hydroxyamine. The mechanism of the LTA oxidation of various enamides is discussed in terms of a common intermediate.