New Palladium-Catalyzed Domino Reaction with Intramolecular Ring Closure of an N-(2-Chloro-3-heteroaryl) arylamide: First Synthesis of Oxazolo[4,5-b] pyrazines

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The synthesis of novel planar heterocycles is at the heart of basic research as such scaffolds constitute key building blocks in important diverse areas of research: drug discovery, material sciences, and pesticides. The well-known benzoxazole is often contained in drug candidates but tweaking its lipophilicity and target interaction points are often desired. In this respect, the oxazolo[4,5-b]pyrazine is an attractive heterocyclic scaffold as it possesses increased water solubility as well as two additional hydrogen bonding acceptors. We here report a new Pd(II)-catalyzed domino reaction comprising the first Pd(II)-assisted intramolecular cyclization of an N-(2-chloro-3-heteroaryl)arylamide and validate its value by application to the first synthesis of 2-substituted oxazolo[4,5-b]pyrazines. We demonstrate that a bidentate phosphorus ligand as well as the presence of an aromatic nitrogen atom is required for the domino reaction to proceed. The robustness of the methodology is confirmed by the synthesis of 23 2-substituted oxazolo[4,5-b]pyrazine analogues in good-to-high yields and containing both electron-withdrawing as well as electron-donating substituents on the reacting arylamide.
OriginalsprogEngelsk
TidsskriftAdvanced Synthesis & Catalysis
Vol/bind356
Udgave nummer5
Sider (fra-til)1047-1055
Antal sider9
ISSN1615-4150
DOI
StatusUdgivet - 24 mar. 2014

ID: 113204866