Asymmetric synthesis of β,β-difluoroamino acids via cross-coupling and Strecker reactions
作者:Xiao-Jin Wang、Fan Zhang、Jin-Tao Liu
DOI:10.1016/j.tet.2007.12.002
日期:2008.2
β,β-Difluoroamino acids were synthesized from commercially available ethyl bromodifluoroacetate using cross-coupling and Strecker reactions as key steps. The coupling reaction of aryl iodides with ethyl bromodifluoroacetate gave the corresponding coupling products, which were transformed to 2-difluoromethyl-1,3-oxazolidines in two steps. Boron trifluoride etherate promoted Strecker reaction of 2-difluoromethyl-1
使用交叉偶联和Strecker反应作为关键步骤,由市售溴二氟乙酸乙酯合成β,β-二氟氨基酸。芳基碘化物与溴二氟乙酸乙酯的偶合反应得到相应的偶合产物,将其分两步转化为2-二氟甲基-1,3-恶唑烷。三氟化硼醚化物促进的2-二氟甲基-1,3-恶唑烷的Strecker反应产生了高产率和非对映选择性的α-氨基腈。除去手性助剂并水解腈基后,获得具有73%ee的β,β-二氟苯丙氨酸。在腈基水解过程中发生部分消旋。