Aza-Michael addition of chiral hydrazines to alkylidene malonates
作者:Auxiliadora Prieto、Rosario Fernández、José M. Lassaletta、Juan Vázquez、Eleuterio Alvarez
DOI:10.1016/j.tet.2005.03.006
日期:2005.5
The conjugate spontaneous addition of chiral N,N-dialkylhydrazines 1 to dimethyl alkylidene/arylidene malonates 2, 5-10 affords the corresponding beta-hydrazino esters in moderate-to-good yields and selectivities. D-Mannitol-derived hydrazine la afforded best results, mainly due to the higher stability of the products 3, 11-16. (c) 2005 Elsevier Ltd. All rights reserved.
Asymmetric Mannich-Type Addition of Ketene Silyl Acetals and Thioacetals to<i>N,N</i>-Dialkylhydrazones
作者:Rosario Fernández、José María Lassaletta、Elena Díez、Auxiliadora Prieto、Monika Simon、Juan Vázquez、Eleuterio Álvarez
DOI:10.1055/s-2006-926283
日期:——
The choice of the 2,6-diphenylpiperidine moiety as the N,N-dialkylamino auxiliary in simple aliphatic dialkylhydrazones and the use of scandium triflate as the catalyst in aqueous media appear as the key strategies that enable the highly diastereoselective nucleophilic addition of ketene silyl acetals and thioacetals. The reaction proceeds to afford the expected adducts in high yields (88-98%) and diastereomeric ratios of up to 99:1. N-N bond cleavage of adducts affords enantiomerically pure β-amino esters.