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Title: Enhanced hydrogenation activity and diastereomeric interactions of methyl pyruvate co-adsorbed with R-1-(1-naphthyl)ethylamine on Pd(111)

Unmodified racemic sites on heterogeneous chiral catalysts reduce their overall enantioselectivity, but this effect is mitigated in the Orito reaction (methyl pyruvate (MP) hydrogenation to methyl lactate) by an increased hydrogenation reactivity. Here, this effect is explored on a R-1-(1-naphthyl)ethylamine (NEA)-modified Pd(111) model catalyst where temperature-programmed desorption experiments reveal that NEA accelerates the rates of both MP hydrogenation and H/D exchange. NEAþMP docking complexes are imaged using scanning tunneling microscopy supplemented by density functional theory calculations to allow the most stable docking complexes to be identified. The results show that diastereomeric interactions between NEA and MP occur predominantly by binding of the C=C of the enol tautomer of MP to the surface, while simultaneously optimizing C=O...H2N hydrogen-bonding interactions. In conclusion, the combination of chiral-NEA driven diastereomeric docking with a tautomeric preference enhances the hydrogenation activity since C=C bonds hydrogenate more easily than C=O bonds thus providing a rationale for the catalytic observations.
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [1]
  1. Univ. of Wisconsin-Milwaukee, Milwaukee, WI (United States)
  2. Univ. of Wisconsin-Milwaukee, Milwaukee, WI (United States); Univ. of Illinois at Urbana-Champaign, Champaign, IL (United States)
Publication Date:
OSTI Identifier:
1326641
Grant/Contract Number:
FG02-03ER15474; SC0008703
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Univ. of Wisconsin, Milwaukee, WI (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY