Vapour-solid interactions for SMSB and asymmetric amplification of pyrimidine and pyridine aldehydes

Abstract

In the last 25 years, the addition of diisopropylzinc to pyrimidine carbaldehydes, known nowadays as the Soai reaction, has drawn the attention of many research groups, not only as it is to date the only chemical reaction offering the chance to study the phenomenon of asymmetric autocatalysis in conjunction with high amplification of enantiomeric excess, but also for the remarkable property to give rise to high ee% even under absolute conditions. Absolute asymmetric synthesis produces chiral molecules in absence of any chiral polarization and is often speculated as possible explanation for the origin of homochirality. This thesis work deepens the knowledge of the Soai reaction performed under absolute conditions and under the less explored heterogeneous vapour-solid reaction conditions. In order to gain information on the long-speculated Soai reaction mechanism, the Soai reagent was encapsulated in UiO Metal-Organic Frameworks (MOFs). The MOFs were used as nano-reactors to probe confinement effects on the catalytically active species. In addition, the vapour-solid reactions revealed some unreported side products, in particular a chiral ester. This observation provides evidence for some recent debated transient intermediates, and opens new perspectives in the elucidation of the mechanism of amplification of chirality in the Soai reaction.