Enantioselective Reactions on a Au/Pd(111) Surface Alloy with Coadsorbed Chiral 2-Butanol and Propylene Oxide

Abstract

The coadsorption of R-and S-propylene oxide with R-2-butanol was studied on a dilute Au/Pd(111) alloy containing ∼8% gold using temperature-programmed desorption and reflection absorption infrared spectroscopy. Alloy formation strongly affects the surface chemistry of these molecules as compared to clean Pd(111). A portion of the propylene oxide decomposes to form CO and ethylidyne species on the alloy, while on clean Pd(111), it adsorbs reversibly. 2-Butanol reacts to form a 2-butoxide species on the alloy that either rehydrogenates to form 2-butanol or undergoes a β-hydride elimination reaction to yield 2-butanone. Coadsorption of R-2-butanol with either R-or S-propylene oxide led to a larger 2-butanone yield in the presence of S-propylene oxide with an enantiomeric excess (ee) of ∼14%. This led to an enantioselective depletion of the 2-butoxide species such that the subsequent 2-butanol formation is highly enantioselective, with 100% ee.

Chirality in metals: An asymmetrical journey among advanced functional materials

“…74 Although there are many examples of the formation of chiral structures on surfaces via functionalisation, the observation of their enantioselectivity still represents a challenge. 75,76 Inherently chiral metallic surfaces…”

Viewing and Inducing Symmetry Breaking at the Single‐Molecule Limit

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Industrially, the selective conversion of prochiral reagents to chiral products is a crucial step in the production of a variety of asymmetric pharmaceuticals. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Industrially, the selective conversion of prochiral reagents to chiral products is a crucial step in the production of a variety of asymmetric pharmaceuticals.…”

“…Ever since Pasteur used tweezers to manually separate enantiopure crystals of sodium ammonium tartrate, 1 the idea of chirality has fascinated scientists. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Industrially, the selective conversion of prochiral reagents to chiral products is a crucial step in the production of a variety of asymmetric pharmaceuticals. While this feat is accomplished using either chiral catalysts or crystallization, many external influences have been shown to be capable of inducing such symmetry breaking, including circularly polarized light, [21][22][23] spin-polarized electrons, 24 and combinations of unpolarized light and magnetic fields.…”

“…While this feat is accomplished using either chiral catalysts or crystallization, many external influences have been shown to be capable of inducing such symmetry breaking, including circularly polarized light, [21][22][23] spin-polarized electrons, 24 and combinations of unpolarized light and magnetic fields. 25 Pioneering studies have made great strides towards explaining these various interactions; [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] however, many of the fundamental mechanisms by which chirality is transferred at the molecular level are not yet fully understood. It is also a great challenge to design experimental protocols with which to study these phenomena in a quantitative and reproducible manner.…”

Asymmetric Thioethers as Building Blocks for Chiral Monolayers

“…In the arena of chiral assembly, tartaric acid [2][3][4][5][6][7][8][9][10], cinchona alkaloids [11][12][13] and heptahelicene [14][15][16] are among the most commonly studied molecules. Several reports in the literature have revealed that chiral adlayers on achiral surfaces exhibit enantiospecific interactions with chiral probe molecules [17][18][19][20]. For example, (S)-propylene oxide exhibits a preference for adsorption on a Pt(111) surface modified with (S)-butoxide over an identical surface modified with (R)-butoxide, with the former system adsorbing 35% more of the probe molecule than the latter [18].…”