Stereoselective Palladium-Catalyzed Functionalization of Homoallylic Alcohols: A Convenient Synthesis of Di- and Trisubstituted Isoxazolidines and β-Amino-δ-Hydroxy Esters
作者:Andrei V. Malkov、Maciej Barłóg、Lucie Miller-Potucká、Mikhail A. Kabeshov、Louis J. Farrugia、Pavel Kočovský
DOI:10.1002/chem.201102716
日期:2012.5.29
Enantiopure, Boc‐protected alkoxyamines 12 and 13, derived from the readily available homoallylic alcohols 4 via a reaction that involves either inversion or retention of configuration, undergo a diastereoselective Pd‐catalyzed ring‐closing carbonylative amidation to produce isoxazolidines 16/17 (≤50:1 diastereoisomer ratio (d.r.)) that can be readily converted into the N‐Boc‐protected esters of β‐amino‐δ‐hydroxy
对映体纯的Boc保护的烷氧基胺12和13通过易于转化的或保留构型的反应从易得的均丙醇4衍生而来,进行非对映选择性的Pd催化的闭环羰基酰胺化反应生成异恶唑烷16/17(≤50 1:1的非对映异构体比率(dr)可以很容易地转化为N -Boc保护的β-氨基-δ-羟基酸的酯及其γ取代的同系物37。关键的羰基化环化过程是通过跨CC键的钯和氮亲核试剂的不寻常的顺式加成而进行的(19 → 21),如15的反应所揭示,得到具有高非对映选择性的异恶唑烷18。