- Sequential copper-catalyzed vinylation/ cyclization: An efficient synthesis of functionalized oxazoles
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A modular and practical synthesis of highly substituted oxazoles has been developed. The transformation consists of a sequential copper-catalyzed amidation of vinyl halides followed by cyclization promoted by iodine. A wide variety of functionalized oxazo
- Martin, Ruben,Cuenca, Ana,Buchwald, Stephen L.
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p. 5521 - 5524
(2008/09/17)
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- N-Vinylketenimines
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The title compounds 5 are generated in situ from N-vinyliminotriphenylphosphoranes 1 and ketenes 2 in a Wittig-type reaction.The phosphoranes are useful intermediates for the preparation of numerous heterocycles as illustrated by the formation of 1,3-oxazines 8, pyridinones 9, pyrimidinones 10 and 1,3-thiazines 11.Water adds readily to 5 to yield vinylacetamides 7, whereas thermal rearrangement gives rise to the isoquinoline 4 or the spiro system 6, respectively.Under very mild conditions, crystalline precursors (type 3) of the N-vinylketenimines, which still contain the triphenylphosphonio group, have been isolated.These react like the N-vinylketenimines generated in situ, giving however less byproducts. Key Words: Phosphorus ylides / Ketenes / Ketenimines
- Capuano, Lilly,Braun, Claudia,Kuehn, Frank
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