Asymmetric hydrogenation reaction of dehydro-α-amino acid (i.e., α-amino ester) over cinchonidine (CD) modified Pd catalyst has been studied by an array of in situ infrared spectroscopic methods, including transmission, diffuse reflectance (DR), and attenuated total reflectance (ATR). Transmission FTIR spectra probed the hydrogenation reaction process, revealed OH–O and NH–N hydrogen bonding interactions between the adsorbed CD and during the reaction. DR and ATR spectra of the hydrogenation reaction under different conditions, which are consistent with but slightly different from the transmission spectra, evidenced the successful hydrogenation of the compound. The incorporation of DR and microfluidics flow-through design allowed us to investigate the adsorption of CD on the Pd surface efficiently. The results revealed that the N-bonded CD on Pd surface in a tilted configuration had increased abundance on the Pd surface with high coverage. These valuable insights provided an image of the reaction pathway to the prochiral structure (precursor state).

Asymmetric Hydrogenation of α-Amino Ester Probed by FTIR Spectroscopy

Long Zhang†, Mehdi Lohrasbi‡, Uma Tumuluri‡, and Steven S. C. Chuang*†

† Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, United States

‡ Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325-3906, United States

Org. Process Res. Dev., Article ASAP

DOI: 10.1021/acs.oprd.6b00222

*E-mail address: schuang@uakron.edu.

http://pubs.acs.org/doi/abs/10.1021/acs.oprd.6b00222

---

Catalytic asymmetric synthesis plays an important role in pharmaceutical and natural products synthesis. Homogeneous asymmetric catalysis has been well-developed over the past decades, while heterogeneous asymmetric catalysis has not undergone similar development due to the difficulty in investigating the interactions among the catalyst, the reactant, and the chiral modifier under reaction conditions. Heterogeneous catalysis exhibits unique features including (i) easiness of product/catalyst separation and catalyst regeneration, (ii) good chemical and physical stability, and (iii) feasibility in continuous processes.These features make it meaningful to investigate the molecular interactions and reactions on the surface of heterogeneous catalysts.

Fourier transform infrared (FTIR) spectroscopy is a versatile tool to provide insights into these interactions and reactions. There are three commonly used FTIR techniques—transmission, diffuse reflectance, and attenuated total reflectance (ATR). With proper design of in situ cells, these FTIR techniques can be used to probe the molecular interactions and reactions at the bulk and catalyst surface under reaction conditions.

Reaction Schematics and the Structure of Cinchonidine

Steven S. C. Chuang

Dr. Steven S.C. Chuang

Director, FirstEnergy Advanced Energy Research Center
Professor
Department of Polymer Science
Phone: 330-972-6993
Email: chuang@uakron.edu

---

Dr. Chuang's Research Website

http://schuang.uakron.edu

Education

• 1985 Ph.D., Chemical Engineering, University of Pittsburgh
• 1982 M.S., Chemical Engineering, New Jersey Institute of Technology
• 1977 Diploma, Chemical Engineering [5yr. program], National Taipei Inst. of Tech.

Contact Information

Dr. Steven S.C. Chuang
The University of Akron
Department of Polymer Science
Akron, Ohio 44325-3909

Email: chuang@uakron.edu
Voice: (330) 972-6993

Research Interests

• Professor Chuang investigates the structure of adsorbed species and its reactivity by transient infrared (IR) techniques. These techniques combined with traditional characterization methods such as XRD, UV-Vis, NMR, SEM, and TEM have been used for studying the nature of adsorbed species and reaction pathways during oxygenate synthesis, hydroformylation, partial oxidation, reduction of nitric oxide, nitric oxide decomposition, oxidative carbonylation, photocatalytic oxidation and reduction, carbon dioxide adsorption, reactions on solid oxide fuel cell catalysts, and synthesis organic/inorganic hybrid materials. The objectives of his research program are (i) developing an understanding of the reactivity of adsorbed species and its associated sites, (ii) using mechanism information to guide catalyst and sorbent preparation, and (iii) scaling up of catalytic and adsorption processes from laboratory scale to the pilot scale.

Faculty Profile [PDF]

http://www.uakron.edu/cpspe/documents/faculty-profiles/FacultyProfile-Chuang.pdf

////////////////