Sintesi di molecole organiche enantiomericamente arricchite con l'uso della catalisi organica

The main topic of this thesis is the use of organocatalysis to synthesize organic compounds enantiomerically enriched. The first matter is about the synthesis of α-amino thioester derivatives through a tandem condensation-intramolecular rearrangement-protonation, this is a conceptually novel chiral Brønsted base/ Brønsted acid catalytic method that provides a number of important synthetic building blocks in good yields and with moderate and good enantioselectivities. The second topic is concerned to the synthesis of aldols derivatives of pyridine carbaldehydes functionalized in different positions using simple amino acids derivatives as catalysts, for example L-proline, L-pyrrolidine tetrazole and so on. This is important because is necessary to found news synthetic methods to produce pyridines nucleus that are very important building block for drugs. Following it is illustrated a preliminary result of a new methodological approach to the synthesis of enantiomerically enriched cyclopentanones starting from cyclobutanones and spirocyclopentanones, it is possible to expand the ring through an organocatalysed Michael reaction. This new approach takes advantages of the introduction of the α,β-unsatured aldehyde function on cyclobutanones. Finally, supramolecular interactions by halogen bonding are described. These occurs between enatiomerically enriched aldols benzothiophene derivatives, synthesized by means of organocatalysed reactions. These kinds of interactions are strongly important in supramolecular chemistry but also in biochemistry, materials and crystal engineering

Sintesi di molecole organiche enantiomericamente arricchite con l'uso della catalisi organica

The main topic of this thesis is the use of organocatalysis to synthesize organic compounds enantiomerically enriched. The first matter is about the synthesis of α-amino thioester derivatives through a tandem condensation-intramolecular rearrangement-protonation, this is a conceptually novel chiral Brønsted base/ Brønsted acid catalytic method that provides a number of important synthetic building blocks in good yields and with moderate and good enantioselectivities. The second topic is concerned to the synthesis of aldols derivatives of pyridine carbaldehydes functionalized in different positions using simple amino acids derivatives as catalysts, for example L-proline, L-pyrrolidine tetrazole and so on. This is important because is necessary to found news synthetic methods to produce pyridines nucleus that are very important building block for drugs. Following it is illustrated a preliminary result of a new methodological approach to the synthesis of enantiomerically enriched cyclopentanones starting from cyclobutanones and spirocyclopentanones, it is possible to expand the ring through an organocatalysed Michael reaction. This new approach takes advantages of the introduction of the α,β-unsatured aldehyde function on cyclobutanones. Finally, supramolecular interactions by halogen bonding are described. These occurs between enatiomerically enriched aldols benzothiophene derivatives, synthesized by means of organocatalysed reactions. These kinds of interactions are strongly important in supramolecular chemistry but also in biochemistry, materials and crystal engineering

Halogen and Hydrogen Bonding Benzothiophene Diol Derivatives: A Study Using ab initio Calculations and XRay Crystal Structure Measurements

The aim of this study is to describe and compare the supramolecular interactions, in the solid state, of chloro-, bromo-, and iodobenzothiophene diols. The compounds were obtained through organo-catalyzed reactions starting from 3-substituted halobenzothiophene carbaldehydes. Energies of the noncovalent interactions were obtained by density functional theory calculations. Bond distances and angles were found to be in accordance with those determined by X-ray structure analysis. anti-Bromobenzothiophene derivatives showed strong halogen ···p interactions between bromine and the heterocyclic phenyl ring, corresponding to an energy of 7.5 kcalmol1. syn- Bromo and syn-iodo derivatives appeared to be isostructural, showing X···O (carbonyl) interactions, p stacking, and formation of extended hydrogen bonding networks. In contrast, the chloro derivatives displayed no halogen bonding interaction

Enantioselective organocatalytic rearrangement of α-acyloxy- β-keto sulfides to α-acyloxy thioesters

The first highly enantioselective organocatalytic rearrangement of α-acyloxy-β-keto sulfides to α-acyloxy thioesters has been developed which provides a number of important synthetic building blocks in high yield and with excellent enantioselectivities (ee: up to 92%)