A New Diastereoselective Synthesis of Enantiomerically Pure 1,2-Oxazine Derivatives by Addition of Lithiated Methoxyallene to Chiral Nitrones
作者:Wolfgang Schade、Hans-Ulrich Reissig
DOI:10.1055/s-1999-2662
日期:1999.5
Addition of lithiated methoxyallene 2 to nitrones provided hydroxylamine derivatives which usually undergo very fast cyclization to 3,6-dihydro-2H-1,2-oxazines. Chiral nitrones 5, 8, or 10 which furnished 1,2-oxazines 6, 9, and 11 with excellent syn diastereoselectivities are of particular interest. By precomplexation of nitrone 5b with diethylaluminum chloride 1,2-oxazine 6b was produced with excellent
Stereoselective grignard reactions to α-amino nitrones. Synthesis of optically active α-aminohydroxylamines and 1,2-diamines
作者:Pedro Merino、Ana Lanaspa、Francisco L. Merchan、Tomas Tejero
DOI:10.1016/s0957-4166(97)00250-4
日期:1997.7
α-Aminohydroxylamines are formed stereoselectively from the nucleophilic addition of phenylmagnesium bromide to α-amino nitrones. In contrast, the addition of methylmagnesium bromide occurs in a stereorandom fashion. Nevertheless it is possible to achieve a complete syn selectivity by diprotecting the α-amino group in the starting nitrone. Hydrogenation of the obtained α-amino hydroxylamines followed