Evaluation of the Katsuki-Sharpless Epoxidation Precatalysts by ESI-FTMS, CID, and IRMPD Spectroscopy

Author(s)

Fernandes, Andre Santos ^[1] ; Maitre, Philippe ^[2] ; Correra, Thiago Carita ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Chem, Dept Fundamental Chem, Av Prof Lineu Prestes 748, BR-05508000 Sao Paulo, SP - Brazil

^[2] Univ Paris Saclay, Univ Paris Sud, CNRS, URM8000, Lab Chim Phys, F-91405 Orsay - France

• Document type: Journal article
• Source: Journal of Physical Chemistry A; v. 123, n. 5, p. 1022-1029, FEB 7 2019.
• Web of Science Citations: 1

Abstract

The Katsuki-Sharpless epoxidation reaction is one of the most recognized chiral catalytic reactions, allowing for chiral epoxides to be used as starting materials for a series of synthetic pathways. The complete understanding of this reaction mechanism depends on the identification and description of species formed from Ti(IV) alkoxides and alkyl tartrates precatalysts. Despite previous reports on the nature of a bimetallic catalyst based on IR spectroscopy and NMR analysis, some debate remains. Therefore, we carried out mass spectrometry analysis by direct extraction of the ions from the reaction media by ESI(-)-FT-ICR and evaluated the observed ions by CID and IRMPD experiments. These techniques allowed us to detect carboxylates that correlate to the species in the reaction media and to confirm the actual presence of the titanium-tartrate complexes in solution. Our IRMPD results suggest the carboxylate dimer as an asymmetric species with two tartrates coordinated to a single Ti atom, while the other Ti center is coordinated by labile alkoxydes that could be easily exchanged by the organic peroxide and the substrate, allowing the epoxidation reaction to take place. (AU)

• FAPESP's process: 15/11769-9 - Isolation of Sharpless reaction intermediates epoxidation and characterization of these species by theoretical calculations
• Grantee: André Santos Fernandes
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 14/15962-5 - Reaction mechanism of asymmetric catalysts by mass spectrometry and gas-phase vibrational ion spectroscopy
• Grantee: Thiago Carita Correra
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 15/08539-1 - Multi-User Equipment approved in grant 2014/15962-5: ion trap mass spectrometer modified to perform infrared vibrational spectroscopy (IRMPD)
• Grantee: Thiago Carita Correra
• Support Opportunities: Multi-user Equipment Program