Over the last decade, with the surge in the development of organocatalysis, many processes involving chiral ion pairs have emerged as powerful tools in the design of new efficient organocatalysts. This tutorial review focuses on the recent evolutions of these organocatalytic systems in which both anionic and cationic parts are working in a cooperative fashion in order to develop unique catalytic processes which outperform the existing approaches. In this respect, chiral ion pairs opened new avenues in the design of bifunctional organocatalysts by means of combinatorial approaches.
A chiral quaternary ammonium amide was generated in situ from N,O-bis(trimethylsilyl)-A C H T U N G T R E N N U N G acetamide (BSA) as non-nucleophilic Brønsted base precursor and the combination of chiral quaternary ammonium halide/sodium aryloxide as chiral Lewis base. This system was applied to an anti-selective organocatalytic direct vinylogous aldol (ODVA) reaction of (5H)-furan-2-one derivatives with aldehydes. Several 5-(1'-hydroxy)-g-butenolides were obtained in good diastereomeric ratios (up to 95/5) and excellent enantioselectivities (up to 94%) with both aliphatic or (hetero)aromatic aldehydes, so providing a rare example of general and efficient conditions for the ODVA reaction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.