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Oxazoles are among the most important heterocyclic scaffolds in the fields of natural products and medicinal chemistry. Herein is developed a tandem reaction for the synthesis of a diverse array of 4,5-difunctionalized oxazoles utilizing easily-accessible ethyl 2-isocyanoacetate and aldehydes (26 examples, 31–83% yields). This cascade reaction is facilitated by catalytic CuBr and molecular oxygen as the oxidant. The process involves a catalytic cycloaddition oxidative dehydroaromatization mechanism. The broad aldehyde substrate scope, mild reaction conditions, and atom economy make this protocol an attractive alternative to access functionalized oxazoles.
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Urea Ligand‐Promoted Chainwalking Heteroannulation for the Synthesis of 6‐ and 7‐membered Azaheterocycles
Abstract Typical approaches to heterocycle construction require significant changes in synthetic strategy even for a change as minor as increasing the ring size. The ability to access multiple heterocyclic scaffolds through a common synthetic approach, simply through trivial modification of one reaction component, would enable facile access to diverse libraries of structural analogues of core scaffolds. Here, we show that urea‐derived ligands effectively promote Pd‐mediated chainwalking processes to enable remote heteroannulation for the rapid construction of six‐ and seven‐membered azaheterocycles under essentially identical reaction conditions. This method demonstrates good functional group tolerance and effectively engages sterically hindered substrates. In addition, this reaction is applicable to target‐oriented synthesis, demonstrated through the formal synthesis of antimalarial alkaloid galipinine.
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- PAR ID:
- 10581659
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 30
- Issue:
- 66
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/chem.202402587
