ChemInform Abstract: Novel Synthesis of Medium-Sized Oxa-Heterocycles by Palladium-Catalyzed Intramolecular Heck Reaction (original) (raw)

Novel Synthesis of Medium-Sized Oxa-Heterocycles by Palladium-Catalyzed Intramolecular Heck Reaction. -An efficient method for the synthesis of eight membered oxa-heterocycles is developed. -(MAJUMDAR*, K. C.; CHATTOPADHYAY, B.; RAY, K.; Tetrahedron Lett. 48 (2007) 43, 7633-7636; Dep. Chem., Univ. Kalyani, Kalyani 741 235, India; Eng.) -Mais 05-168

Synthesis of Five- and Six-Membered Heterocycles Through Palladium-Catalyzed Reactions

ChemInform, 2004

Over the last years, palladium-catalyzed coupling reactions have been extensively studied and the names of Heck, Stille, Suzuki and Sonogashira are well known for their contribution to this chemistry. Extension of the coupling reactions allowing introduction of heteroatoms have followed and the Buchwald-Hartwig reaction is now a concept for this chemistry. Another achievement in this field is the possibility offered by the methodology to acceed to heterocyclic compounds either through a direct construction of the heterocyclic ring or by a two-step procedure (coupling followed by an heteroannulation). We are in the following paper going to review these ways of preparing heteroaromatic compounds either as single ring system or condensed to other aromatic rings. I) PREPARATION OF FIVE-MEMBERED AROMATIC HETEROCYCLES IN A ONE-STEP PROCEDURE I-1) Synthesis of Pyrroles The Sonogashira coupling of an alkyne chain containing a tosylhydrazone (1) with aryl iodides led to the formation of 2-benzylsubstituted pyrroles (2) in 40-70% yield; in the absence of aryl iodide, 2-methylsubstituted pyrroles were obtained [1].

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