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Identifier

000426247

Title

Παραγοντοποίηση ακόρεστων οργανικών ενώσεων καταλυόμενη από νανοσωματίδια χρυσού

Alternative Title

Functionalization of unsaturated organic compounds catalyzed by gold nanoparticles

Author

Κυδωνάκης, Μάριος Α

Thesis advisor

Στρατάκης, Μανώλης

Reviewer

Βασιλικογιαννάκης, Γεώργιος
Κατερινόπουλος, Χαράλαμπος
Σμόνου, Ιουλία
Λυκάκης, Ιωάννης
Σπύρος, Απόστολος
Παυλίδης, Ιωάννης

Abstract

This dissertation describes new applications of supported gold nanoparticles in catalysis of organic transformations. More specifically, describes the diboration as well as the silaboration of alkynes and allenes, the selective borylation of conjugated carbonyl compounds and the hydrosilylation and reduction of carbenes generated by α-diazo carbonyl compounds. This dissertation is organized as follows: In the First Chapter is descripted the diboration of alkynes catalyzed by gold nanoparticles supported on titania (Au/TiO₂). A series of terminal and internal alkynes bearing several functional groups undergo the addition of pinB-Bpin (pin: pinacolato) in a highly stereoselective manner. Furthermore, by taking advantage of the catalyst ability to activate the σ Si-Si bond, we achieved the indirect silaboration of alkynes by utilizing several commercially available 1,2-disilanes and the pinB-Bpin. In the Second Chapter the diboration and silaboration of allenes are descripted. Both the diboration and silaboration occur exclusively on the terminal double bond, and furthermore in the case of the silaboration, the Si moiety is exclusively attached on the C_sp and the B moiety on the external C_sp², selectivity that is rare for this kind of addition. Mechanistic studies, including the use of suitable substituted cyclopropyl allenes as sensitive probes, unveil the creation of an η¹ allylic complex after the activation of the σ B-B and Si-B bonds on the active catalytic sites. In the Third Chapter is descripted the ability of Au/TiO₂ to catalyze the β-borylation of conjugated carbonyl compounds using the pinB-Bpin as the borylating agent. The reaction does not require any base or protic reagent, suggesting a different mechanistic scenario contrary to the so far known analogous methodologies. Most importantly, it is shown that in the presence of Au/TiO₂, PhMe₂Si-Bpin delivers the Bpin on the β-C, in sharp contrast to the known catalytic methodologies where the Si moiety is attached on the β-C, underlying the chemoselectivity of the PhMe2Si-Bpin addition catalyzed by gold nanoparticles. In the Fourth Chapter is descripted the unpresented ability of Au/TiO₂ to catalyze the insertion of carbenes into the σ Si-H bond. This kind of reaction was unknown in the area of gold chemistry and the first methodology under heterogeneous conditions. Mechanistic studies unveiled a different mechanistic pathway than that is widely known for this type of reaction. More specifically, it is proposed that the transformation involves two modes of catalytic activation, that is the formation of a nucleophilic Au carbene on the surface of nanoparticle via expulsion of N₂ and the simultaneous activation of the Si-H σ bond, followed by coupling of the chemisorbed species. Finally, it is shown the ability of Au/TiO₂ to catalyze the reduction of carbenes generated by α-diazo carbonyl compounds by using the commercially available NaBH₄.

Language

Greek

Subject

A-diazo carbonyl compounds

Alkynes

Allenes

Au Nanoparticles

Borylation

Carbenes

Conjugated carbonyl compounds

Diboration

Hydrosilylation