Direct and stereoselective (syn or anti) Ti-mediated Mannich-type reactions

February 29, 2024

• Title:       

  Direct and stereoselective (syn or anti) Ti-mediated Mannich-type reactions

• Image Source:

  Ti-mediated direct and highly stereoselective Mannich reactions between esters and oxime ethers

• Mark:

  Scheme 1

• Associated context:

  Direct methods using simple  esters as nucleophiles are considerably limited compared with those of ketones because of their lower enolization ability, and in addition the Mannich reaction generally utilizes relatively unstable imines for the counter electrophiles. Oxime ethers are well-known superior isosters to imines due to easier preparation and inherently  higher stability, especially for reliable aliphatic aldoximes derived from enolizable aldehydes. The reaction using oxime ethers, therefore, has a clear advantage over that of imines, because of its  wide variation. As part of our continuing studies of Ti-Claisen condensation and related reactions, we disclose here direct and stereoselective (syn or anti) Ti-mediated Mannich-type reactions between three types of esters and methyl oxime ethers (aldoximes  and aryloximes, E and Z mixtures) (Scheme 1).