Reaction Between Grignard Reagents and Heterocyclic N-oxides Synthesis of Substituted Pyridines, Piperidines and Piperazines
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Efficient, mild and completely regioselective synthesis of substituted pyridines.
Addition of Grignard reagents to pyridine N-oxides in THF at low temperature (-78 to -20 degrees C) and treatment with TFAA provides an efficient general procedure for synthesis of substituted pyridines. The method is compatible with a range of functional groups such as esters, halogens and nitriles.
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A simple and efficient protocol for the construction of substituted piperazines, piperidines, thiomorpholines, decahydroquinolines, perhydrocyclopenta[b]pyridine, and pyrrolidines bearing N-hydroxy substituents through intramolecular reductive cyclization of diketoximes using sodium cyanoborohydride is described.
متن کاملChem. Pharm. Bull. 53(1) 60—63 (2005)
construction of various heterocyclic rings. The reactions of pyrylium or thiopyrylium salts, six-membered cationic heteroaromatics containing an oxygen or sulfur atom, with nitrogen-containing nucleophiles to afford a variety of nitrogen-containing heterocyclic compounds provide one of the most effective examples of the ring transformation. Sixmembered heterocycles such as pyridines, quinolines...
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Piperazine ranks within the top three most utilized N-heterocyclic moieties in FDA-approved small-molecule pharmaceuticals. Herein we summarize the current synthetic methods available to perform C-H functionalization on piperazines in order to lend structural diversity to this privileged drug scaffold. Multiple approaches such as those involving α-lithiation trapping, transition-metal-catalyzed...
متن کاملDiastereoselective synthesis of CF3-substituted, epoxide-fused heterocycles with β-(trifluoromethyl)vinylsulfonium salts.
CF(3)-substituted vinyl diphenylsulfonium triflate is an effective annulation reagent for the formation of α-CF(3) substituted, epoxide-fused heterocycles (pyrrolidines, piperidines, and tetrahydrofurans). This simple method affords a variety of valuable heterocyclic building blocks in a highly diastereoselective manner (dr >20:1).
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تاریخ انتشار 2009