Recent advances in the asymmetric catalytic construction of oxa-quaternary carbon centers

Abstract

Compounds bearing oxa-quaternary carbon centers, such as chiral tertiary alcohols, ethers, esters, and acetals are widely found in a number of bioactive compounds, natural products, agrochemicals and drugs. Besides, they...

Enantioselective construction of spirodihydrofuran oxindoles via one-pot organo-/iodine sequential catalysis

“…Therefore, considerable advances have been achieved in developing effective approaches for their catalytic asymmetric synthesis. 1 Among these approaches, the organocatalytic asymmetric construction of two vicinal quaternary stereocenters is a daunting challenge. The daunting challenge might be tackled by only a limited number of known strategies: first, the addition reactions between a prochiral tertiary carbon and bisubstituted or trisubstituted electron-deficient olefins or imines (Scheme 1a), 2 second, the difunctionalization or cascade reactions of substituted alkanes or alkenes, such as the named double alkylation, aldol reaction, and Michael addition (Scheme 1b), 3 third, the cyclization of substituted alkenes (Scheme 1c), 4 and fourth, the direct or halogen-mediated coupling reactions (Scheme 1d).…”

Asymmetric synthesis of bicyclic pyran scaffolds bearing two oxa-quaternary stereocenters via zinc-catalyzed [5 + 1] annulations

“…Bicyclic pyran scaffolds 1 are widely found as bioactive heterocycles in a number of natural products. Furthermore, oxa-quaternary carbon centers 2 are ubiquitous key structural motifs prevalent in various biologically active compounds and pharmaceutical agents (Fig. 1).…”