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Identifier

000283810

Title

Χημειο-και τοπο-εκλεκτικότητα κατά την φωτοξείδωση βενζυλο αλκοολών παρουσία του φωτοκαταλύτη πολυοξομεταλλικό σύμπλοκο του βολφραμίου:μηχανισμοί και συνθετικές εφαρμογές

Author

Λεστάκης, Στέλιος Ιωάννη

Thesis advisor

Ορφανόπουλος, Μιχάλης

Abstract

In the first chapter, the investigation of C-H activation (selectivity) in the decatungstate-sensitized photooxygenation of para-alkyl and para-aryl substituted aromatic alcohols by both product analysis and kinetic data has been reported. The results of these photooxygenations suggest a high intramolecular chemoselectivity between the benzylic alcohol and the para-alkyl or aryl positions. In all cases aryl ketones were observed as the only or major product. Product analysis of these reactions with gas chromatography and 1H NMR spectroscopy indicates that no significant amount of the C-C bond cleavage products was observed. Continuous photolysis results of the oxygenation of para-substituted aryl alkanols confirm that the C-H(alkyl) activation of the para-position depends on the nature of the para-substituent and follows the order Et > PhCH2 > Ph2CH > iPr > Me. This result supports a steric interaction between the R substituent of the aryl alcohol and the incoming decatungstate reactive intermediate which also affect the observed amount of C-H(alcohol) versus C-H(alkyl) activation. These results are consistent with a step-wise mechanism with the hydrogen atom abstraction in the rate-determining step. In the second chapter , an efficient and regioselective decatungstate photosensitized oxidation of aryl alcohols and aryl diols in the presence of molecular oxygen has been reported. The 1-aryl-1-alkanols were oxidized in synthetic scale to the corresponding aryl ketones, while 1,2- and 1,3-aryl diols yielded mostly the 2-hydroxyl and 3-hydroxyl aryl ketones. The results are also consistent with a step-wise mechanism with the hydrogen atom abstraction in the rate-determining step.

Language

Greek

Issue date

2006-04-01

Collection

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

Type of Work--Post-graduate theses

Permanent Link

https://elocus.lib.uoc.gr//dlib/e/3/0/metadata-dlib-2006lestakis.tkl

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