Structure and Mechanism in Aerobic Alkene Epoxidations Promoted by Ruthenium Complexes of Bis(dihydrooxazole) Ligands

Abstract

Reaction of [RuCl2(NCMe)2(cod)] with bis(dihydrooxazoles) gave [RuCl2(cod)(S,S)-R12C-(C=NCHR 2CR12O)2] (cod = cycloocta-1,5-diene; R1 = H, R2 = CH2Ph or Pri; R1 = Me, R2 = Pri). The benzyl complex has been crystallographically characterised. The IR spectra of the complex of the hexamethyl-substituted compound suggest that the ligand is relatively distorted and this is borne out by crystallographic comparison of the model complexes cis-[W(CO)4(S,S)-R2C(C=NCHPriCR 2O)2] (R = H or Me). Mechanistic studies of the epoxidation of styrene and stilbenes in the presence of isobutyraldehyde and molecular oxygen using the ruthenium complexes as catalysts in the presence and absence of 4-tert-butylcatechol as a radical trap revealed that the metals act as promoters for the production of PriCO3H and that this carries out the epoxidation, either directly or by formation of oxo-ruthenium species.

Department(s)

Chemistry

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1995 Royal Society of Chemistry, All rights reserved.

Publication Date

01 Jan 1995

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