Lewis Acid Catalyzed Cyclization Reactions of Ethenetricarboxylates via Intramolecular Hydride Transfer

Abstract

Catalytic cyclization of amides of ethenetricarboxylate bearing ether and acetal groups has been examined. The reaction of the amides bearing cyclic ether and acetal groups in the presence of Lewis acid such as Sc(OTf) gave spirocyclic piperidine derivatives as major products. The cyclized products may be formed via intramolecular hydride transfer. The reaction mechanism was examined by the DFT calculations. The scope and limitations of the hydride transfer/cyclization reactions of amides of ethenetricarboxylates was investigated, and morpholine formation by intramolecular oxy-Michael addition was also found.

Memory of Chirality in a Flow‐Based System: Enantioselective Synthesis of Quaternary α‐Amino Acids Using Flow Microreactors

“…The principle relies on a memorization of the initial chirality by a global chiral conformation of the intermediate. Therefore this strategy is very sensitive to reaction conditions in particular reaction rate and temperature, and many MOC reactions are either intramolecular or performed at low temperature or both , . We have already developed a 3‐step asymmetric synthesis of quaternary α‐amino acids based on MOC .…”

Hydride Transfer Involved Redox-Neutral Cascade Cyclizations for Construction of Spirocyclic Bisoxindoles Featuring a [3,4]-Fused Oxindole Moiety

“…Inspired by the redox- and step-economy, we intend to develop a strategically distinct route to access spirocyclic bisoxindoles. In this context, we notice that the cascade hydride transfer/cyclization has recently emerged as a powerful tool for construction of various heterocyclic rings owing to its high efficiency and environmental sustainability. − However, the inherent drawbacks of these established reactions, such as the essential dependence of phenyl skeleton as a linker between hydride donors and acceptors (Scheme A), largely limited their applications in the synthesis of diverse natural products and drug intermediates . To address this challenge, we rationally design a new type of substrate decorated with an amine at the C4 position of isatin, which could react with the external nucleophiles to achieve the redox-neutral cascade hydride transfer/cyclization for rapid construction of privileged [3,4]-fused oxindoles.…”

Synthesis of Piperidines via Intramolecular Hydride Transfer from α‐Amino sp3 Carbon Atoms to Ethenetricarboxylate‐Derived Fragments and Further Cyclization

“…Recently, we have reported the Lewis‐acid‐catalyzed cyclization of amides derived from ethenetricarboxylic acid bearing ether and acetal groups to construct piperidine rings (Scheme ) . The reaction utilizes the high electrophilicity of the alkylidenemalonate fragments as Michael acceptors…”