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.
在简单的脂肪族二烷基肼中选择 2,6-二苯基哌啶作为 N,N-二烷基氨基助剂,并在水介质中使用三酸钪作为催化剂,是实现烯酮硅基乙醛和硫代乙醛高非对映选择性亲核加成的关键策略。该反应以高产率(88-98%)和高达 99:1 的非对映比率生成预期的加合物。加合物的 N-N 键裂解产生对映体纯的δ-氨基酯。