Scope, limitations and mechanistic analysis of the HyperBTM-catalyzed acylative kinetic resolution of tertiary heterocyclic alcohols

Abstract

The full scope and limitations of the catalytic acylative kinetic resolution of a range of tertiary heterocyclic alcohols (78 examples, s up to >200) is reported under operationally-simple conditions, using low loadings of a commercially available Lewis basic isothiourea catalyst, HyperBTM (generally 1 mol %). The protocol is highly effective for the kinetic resolution of 3-substituted 3-hydroxyoxindole and α-substituted α-hydroxylactam derivatives bearing up to three potential recognition motifs at the stereogenic tertiary carbinol center. The full power of this methodology has been showcased through the synthesis of highly enantioenriched biologically-active target compounds in both enantiomeric forms. To provide further insight into the reaction mechanism, a detailed kinetic analysis of this Lewis base-catalyzed acylation of tertiary alcohols is reported using the variable time normalization analysis (VTNA) method.