A new class of polystyrene-supported aminocatalysts with a triazole linker from diphenyl prolinol were developed. Their catalytic activity, substrate scope, and reusability were demonstrated in asymmetric α-amination of aldehydes.
Overcoming Thermodynamically Driven Retro‐Diels–Alder Reaction through a Cascade One‐Pot Process Exemplified for a Bio‐Based Platform Chemical
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A cascade process for synthesis and conversion of a thermodynamically labile Diels–Alder adduct proceeds with high conversion of >99 % by coupling of the Diels–Alder reaction with a rapid hydrogenation. A rotating reaction vessel leads to a thin film of the intermediate, which then slowly dissolves into an immediately convertible solution.
In this contribution, we describe a new approach to apply thermodynamically unfavored reactions in synthetic chemistry and to integrate them in cascade processes. By means of a new developed procedure for multi-step one-pot syntheses, we succeeded in nearly completely converting a thermodynamically labile Diels–Alder adduct, which strongly tends to react back, to the target product with high conversion of >99 % and in excellent yield by coupling with a rapid subsequent hydrogenation reaction. In detail, the process is based on the use of a rotating reaction vessel to form a thin product film of the thermodynamically labile Diels–Alder product from 2-methylfuran and maleic acid anhydride (as two bio-based raw materials), which then slowly dissolves into solution and is immediately converted by hydrogenation to the target product. Such a combination of Diels–Alder reaction and hydrogenation in a sequential one-pot process without by-product formation enables the efficient production of the product, which represents a valuable bio-based platform chemical. In addition, this process concept generally opens a perspective for the integration of thermodynamically unfavorable reaction steps in multi-step one-pot cascade processes while obtaining the desired target products in high yields.Zum Volltext
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