Fine Chemical Synthesis

Baiker's work in fine chemical catalysis has enriched three important areas: chemoselective and enantioselective hydrogenation, partial and selective oxidation, and amination.
By systematic studies on enantiodifferentiating heterogeneous Pt-cinchona alkaloid catalysts [3.a], used for the chiral hydrogenation of α-ketoesters, Baiker and his group have greatly advanced the knowledge on these complex catalytic systems. These investigations have lead to the design of promising new enantio-differentiating catalysts based on synthetic amino-alcohol type modifiers. The advantage of these modifiers is that a molecular engineering of both the stereogenic center as well as the anchoring group can be achieved, in contrast to the classical natural cinchona type modifiers. This opportunity has opened the narrow range of substrates that can be transformed enantioselectively. First continuous enantioselective hydrogenation on solid catalysts was reported by the Baiker group. Fundamental experimental and theoretical studies have brought new insight into the functioning of these catalytic systems and uncovered phenomena such as the nonlinearity and switch of enantiodifferentiation observed with chirally modified metal surfaces. The group has extensively studied the mechanism of mild partial oxidations in the liquid phase [3.b] with air as oxidizing agent, using electrochemical methods and in situ spectroscopy such as ATR-IR and XAS. These studies have uncovered several new aspects of the reaction mechanism, which finally resulted in the design of more selective catalysts. In-situ catalyst potential measurements were used to gain information about the working state of the catalyst and for controlling the oxygen flux to the catalytic surface. Based on this concept high molecular weight and heat sensitive reactants such as alcohols and carbonyl compounds can be oxidized selectively using air as oxidant. Another field in oxidation catalysis where Baiker’s group has contributed is catalytic epoxidation [3.c]. They were the first who showed that amorphous titania-silica mixed oxide aerogels possess outstanding properties for the  epoxidation of bulky olefins with alkylhydroperoxides as oxidants. Furthermore, important aspects of the reaction mechanism and catalyst tuning have been uncovered.
Baiker's early studies on amination of alcohols [3.d] have answered several important questions concerning this industrially important reaction. Aspects covered were catalyst design, mechanism, kinetics, and reaction engineering. Based on this knowledge new more economic continuous amination processes, which do not require high pressure were developed.