Enantioselective Synthesis of C<sup>α</sup>-Tetrasubstituted <i>N</i>-Hydroxyl-α-amino Nitriles via Cyanation of Ketonitrones Using Me<sub>2</sub>(CH<sub>2</sub>Cl)SiCN
unprecedented catalytic enantioselective cyanation of ketonitrones enabled by the bifunctional cyanating reagent Me2(CH2Cl)SiCN. This approach allows facile access to optically active N-hydroxyl-α-amino nitriles that are of high synthetic value but difficult to acquire by other methods. The use of bifunctional cyanating reagent Me2(CH2Cl)SiCN not only achieves an enantioselectivity higher than that with
作者:Bruce H. Toder、George B. Mullen、Vassil St. Georgiev
DOI:10.1002/hlca.19900730119
日期:1990.1.31
Adamantanone-derived nitrone 4 and some other keto-nitrones, when reacted with aromatic and aliphatic aldehydes in refluxing toluene or tetrahydrofuran, formed the corresponding aldonitrones (Z)-10, the latter arising from the fragmentation of an initially formed 1,4,2-dioxazolidine 6 to adamantan-2-one and an oxaziridine intermediate 11, which then rearranges to (Z)-10.
Asymmetric hydrosilylation of nitrones using ruthenium(II) phosphine complex catalysts; syntheses of optically active N,N-disubstituted hydroxylamines and secondary amines
Enantioselective hydrosilylation of carbon–nitrogen double bonds of nitrones with diphenylsilane using Ru2Cl4-[(S)-(–)-p-tolbinap]2(NEt3)[p-tolbinap = 2,2′-bis(di-p-tolyphosphino)-1,1′-binaphthyl] catalyst at 0°C gives the corresponding optically active N,N-disubstituted hydroxylamines; up to 91% enantiomeric excess (e.e.) is achieved.
Synthesis of optically active N-hydroxylamines by asymmetric hydrogenation of nitrones with iridium catalysts
作者:Shun-Ichi Murahashi、Teturou Tsuji、Shuichi Ito
DOI:10.1039/a909927l
日期:——
Asymmetric hydrogenation of nitrones with the iridium catalyst
system, prepared from [IrCl(cod)]2, (S)-BINAP, and
NBun4BH4, gives the corresponding
N-hydroxylamines, which are important as biologically active
compounds and precursors of amines, with high enantioselectivity (up to 86%
ee).
The enantioselective reduction of 1,3-dipolarnitrones to hydroxylamines was achieved by Rh(III)-catalyzed asymmetric hydrogenation and transfer hydrogenation. A wide range of chiral N,N-disubstituted hydroxylamines were synthesized with up to 99 % yield and >99 % ee. Mechanistic investigations and DFT calculations were conducted to elucidate the origin of reactivity and enantioselectivity.