Spiro-fused carbohydrate oxazoline ligands: Synthesis and application as enantio-discrimination agents in asymmetric allylic alkylation
作者:Jochen Kraft、Martin Golkowski、Thomas Ziegler
DOI:10.3762/bjoc.12.18
日期:——
partially deprotected under acidic conditions followed by condensation with thiocyanic acid to give an anomeric mixture of the corresponding 1,3-oxazolidine-2-thiones. The anomeric 1,3-oxazolidine-2-thiones were separated after successive benzylation, fully characterized and subjected to palladium catalyzed Suzuki-Miyaura coupling with 2-pyridineboronic acid N-phenyldiethanolamine ester to give the corresponding
在目前的工作中,我们描述了螺-融合的D-果糖和D-psico构型的恶唑啉配体的方便合成及其在不对称催化中的应用。由容易获得的3,4,5-三-O-苄基-1,2-O-异亚丙基-β-D-果糖基葡萄糖和3,4,5-三-O-苄基-1,2-O合成配体-异亚丙基-β-D-psicopyranose。后一种化合物在酸性条件下部分脱保护,然后与硫氰酸缩合,得到相应的1,3-恶唑烷-2-硫酮的端基异构体混合物。连续的苄基化后,分离出端基异构的1,3-恶唑烷-2-硫酮,并充分表征并与2-吡啶硼酸N-苯基二乙醇胺酯进行钯催化的Suzuki-Miyaura偶联,得到相应的2-吡啶基螺-恶唑啉(PyOx)配体。螺-恶唑啉配体在钯催化的丙二酸二甲酯与1,3-二苯基烯丙基乙酸的烯丙基烷基化反应中用作手性配体时,表现出很高的不对称诱导性(最高93%ee)。D-果糖-PyOx配体主要提供(R)-对映体,而D-psico-构型