Victoria Morales

One-step synthesis of a thioester chiral PMO and its use as a catalyst in asymmetric oxidation reactions

The study of key aspects for the heterogenization of chiral homogeneous catalysts is addressed in this work. Two different heterogenization routes were evaluated. On the one hand, the immobilization of a tartaric acid derivative (Sharpless catalyst) was accomplished by following a two-step synthesis methodology. In the first step, the mesoporous support SBA-15 was functionalized with different percentages of mercaptopropyl-(trimethoxy)-silane (MPTMS) through a co-condensation method, obtaining very high degrees of MPTMS incorporation. In the second step, the chiral moiety is anchored onto the previously organically modified silica by means of a thiotransesterification reaction. On the other hand, the second route consisted of the formation of mesoporous structure and chiral ligand immobilization in the walls, simultaneously, in only one step. In this case, the chiral organic functionality was incorporated into the wall silica framework, since the built-organic complex is a bis-silane, obtaining a chiral PMO. Finally, once characterized, the synthesized materials were proved in an asymmetric catalytic test in order to study their enantioselective properties. The chosen reaction was the thioanisole enantioselective sulfoxidation, using cumene hydroperoxide as an oxidant. The materials synthesized by the multi-step method reached 40% enantiomeric excess (ee), while the synthesized one-pot chiral PMO materials reached up to 50% ee. Thereby, materials with the chiral Sharpless ligand incorporated into the three dimensional silica framework were successfully accomplished, as well as its ability to induce higher chirality in the enantiomeric tested reaction than the conventional methods of chiral ligand heterogenization onto a silica framework.

Volatile Organic Compounds Analysis in Breath Air in Healthy Volunteers and Patients Suffering Epidermoid Laryngeal Carcinomas

Exhaled breath contains thousands of gaseous volatile organic compounds (VOCs) that may be used as non-invasive markers of head and neck epidermoid cancer. We hypothesized that solid phase micro-extraction coupled to gas chromatography–mass spectrometry can discriminate patients with epidermoid head and neck cancer from healthy controls by analyzing the gaseous volatile organic compounds, VOC-profile, in exhaled breath, thus identifying some non-invasive biomarkers to be used in early detection. Twenty healthy subjects participated in a cross-sectional study plus 11 patients with epidermoid supraglottic laryngeal cancer. VOCs from T3 supraglottic cancer were clustered distinctly from those of T1 and healthy subjects. Up to seven VOCs were detected differently from healthy volunteers, mainly 2-butanone and ethanol. Thus VOC-patterns of exhaled breath may discriminate patients with epidermoid head and neck cancer from healthy controls.

Direct synthesis and post-oxidation of SBA-15 and MCM-41 functionalized with butenyl groups

Olefins are interesting compounds to anchor onto the surface of silica supports since their reactivity allow to form a large variety of organic functionalities. In this work, the synthesis of mesostructured silicas (MCM-41 and SBA-15 type materials) functionalized with butenyl groups is studied through the use of post-synthetic grafting or direct-synthesis procedures. Results confirm the higher functionalization degree achieved in the final mesostructured materials when using direct synthesis procedures. Unlike MCM-41 materials, which become microporous when high organic content are attached on, SBA-15 type butenyl functionalized silicas keep the features of a mesoporous solid. Post-synthetic and in-situ oxidations of butenyl groups during the preparation of the mesostructured silicas have been carried out using H2O2 as oxidant, leading to materials functionalized with glycol moieties attached to inorganic mesoporous materials, which are attractive to be used as supports for anchoring different catalytic species.