α-Funzionalizzazione organocatalitica enantioselettiva di aldeidi con eterocicli aromatici azotati

In this work, two enantioselective syntheses catalyzed by diphenyl prolinol silyl ethers to alfa-functionalized aldehydes are presented. In the first project, N-benzylpyridinium bromides activated at the C3 position by an electron-withdrawing group (nitro or cyano) are used. The pyridine portion added to the aldehyde losing aromaticity and forming a dihydropyridine derivative. The optimization of the reaction parameters as solvent, base, catalyst, acid co-catalyst and temperature has been reported. Moreover, the generality of the reaction has been proved varying both the pyridiuum salts and the aldehydes. Finally, the relative and absolute configuration of the products were determined and explained assuming a reaction mechanism through the syncline transition state. In the second project, the enantioselective alfa-arylation of aldehydes with isquinoline N-oxides, catalyzed by diphenyl prolinol silyl ethers, has been studied. The activation of the isquinoline N-oxide has been achieved with the use of bromotripyrolidinodiphosphonium hexafluorophosphate (PyBroP). A preliminary study of the optimal reaction conditions has been carried out, which is still underway. Currently, good enantiomeric excesses and moderate to good conversions of reagents have been obtained.