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Identifier

000412998

Title

Χημειοεκλεκτική και τοποεκλεκτική δισιλυλίωση αλκυνίων και αλλενίων από διυδροσιλάνια καταλυόμενη από νανοσωματίδια χρυσού

Alternative Title

Chemoselective and regioselective disilylation of alkynes and allenes by bihydrosilanes catalyzed by gold nanoparticles

Author

Σαριδάκης, Ιάκωβος Ε.

Thesis advisor

Στρατάκης, Μανόλης

Reviewer

Κατερινόπουλος, Χαράλαμπος
Βασιλικογιαννάκης, Γεώργιος

Abstract

In the present scientific dissertation are presented novel methodologies for dehydrogenative disilylations of alkynes and allenes by dihydrosilanes (R₂SiH₂) catalyzed by gold nanoparticles supported on titania (Au/TiO₂). It was found that: A. Au/TiO₂ catalyzes efficiently the dehydrogenative cis-1,2-disilylation of terminal alkynes with dihydrosilanes. It is stressed that such reactivity of dihydrosilanes is unprecedented and stands in contrast to monohydrosilanes (R₂SiH) which in the presence of Au/TiO₂ react with alkynes forming stereoselectively β-(E)-hydrosilylation products. A plausible mechanism is postulated and involves the reaction of the initially formed complex R₂HSi-Au_n-H with a second dihydrosilane molecule forming the reactive complex R₂HSi-Au_n-SiHR₂ (with the simultaneous H₂ elimination) which is added with syn stereochemistry onto the alkyne’s π-system. Further exploitation of the disilylation product involves the Au/TiO₂-catalyzed reactions either with water or with a second alkyne molecule producing substituted 2,5-dihydro-1,2,5-oxadisiloles or 1,4-disila-2,5-cyclohexadienes, respectively, with concomitant H₂ release. B. Au/TiO₂ is an efficient catalyst for the regiospecific and stereoselective β,γ-disilylation of terminal allenes with dihydrosilanes. It is accentuated that such reactivity among dihydrosilanes and allenes is unprecedented and the products are unknown in the literature. It is proposed that the same gold complex (R₂HSi-Au_n-SiHR₂) interacts with the allene and adds exclusively in the least substituted double bond forming the disilylation products with E stereochemistry. Au/TiO₂ also catalyzes the dehydrogenative formation of 3-vinyl-1,2,5-oxadisilolanes via reaction among the disila adducts and a water molecule

Language

Greek

Subject

Αλκύνια

Αλλένια

Ετερογενής κατάλυση

Ηeterogeneous catalysis

Issue date

2017-11-23

Collection

School/Department--School of Sciences and Engineering--Department of Chemistry--Post-graduate theses

Type of Work--Post-graduate theses