作者:John B. Feltenberger、Ryuji Hayashi、Yu Tang、Eric S. C. Babiash、Richard P. Hsung
DOI:10.1021/ol901434g
日期:2009.8.20
Benzyne-[2 + 2] cycloadditions with enamides are described. This effort led to the development of a highly stereoselectivetandem [2 + 2] cycloaddition−pericyclic ring-opening−intramolecular-N-tethered-[4 + 2] cycloaddition for rapid assembly of nitrogen heterocycles.
Chiral enamides 5f–i were found to react with pyrylium ylides to give cycloadducts 6d–i in good yields with an excellent level of stereoselectivity. The chiral auxiliary was successfully removed on hydrogenolysis of compound 6f in continuous flow (H-Cube) resulting in the first asymmetric synthesis of complex amine 8.
catalytic methods that enable highlystereoselective dicarbofunctionalization of alkenes are lacking. Herein, we report the use of readily available chiral vinyl oxazolidinones as effective chiral radical lynchpins to enable practical and diastereoselective (up to 1:78 dr) Fe-catalyzed dicarbofunctionalization with fluoroalkyl halides and hetero(aryl) Grignard reagents. Experimental and computational
Under smooth Eu(fod)3-catalyzed conditions, the inverse-electron demand hetero-Diels−Alder reactions between enantiopure N-vinyl-2-oxazolidinones 1a−f and representative β,γ-unsaturated α-ketoesters proceed with a high degree of endo and facial diastereoselectivity. The elucidation of the stereostructure of these adducts, performed by X-ray analysis or chemical correlation, shows that the endo-selective
Preparation of Chiral<i>N</i>-Vinyl Oxazolidinones by a Simple General Procedure
作者:Robert Dhal、Catherine Gaulon、Gilles Dujardin
DOI:10.1055/s-2003-41443
日期:——
A high yielding, general, and practical procedure for the N-vinylation of 2-oxazolidinones via TMSOTf-promoted dehydroalkoxylation of N,O-acetals is described.