Asymmetric Synthesis of 3,4-Dihydrocoumarin Motif with an All-Carbon Quaternary Stereocenter via a Michael–Acetalization Sequence with Bifunctional Amine-thiourea Organocatalysts
摘要:
Asymmetric domino Michael acetalization reactions of 2-hydroxynitrostyrene and 2-oxocyclohexanecarbaldehyde with a bifunctional thioureatertiary-amine organocatalyst, e.g., the Takemoto catalyst, followed by oxidation providing the 1',3-spiro-2'-oxocyclohexan-3,4-dihydrocoumarin having one all-carbon quaternary stereocenter with excellent diastereo- and enantioselectivities (up to >99% ee), are described. The structures and absolute configurations of the products were confirmed by X-ray analysis.
Observation of neighboring ortho-hydroxyl group participation in organocatalytic asymmetric sequential Michael-lactonization reactions: synthesis of highly substituted chiral spirodihydrocoumarins
作者:Dhevalapally B. Ramachary、R. Madhavachary、M. Shiva Prasad
DOI:10.1039/c2ob07122c
日期:——
A general approach to asymmetric synthesis of highly substituted spirodihydrocoumarins with a quaternary stereocenter was achieved through neighboring ortho-hydroxyl group induced sequential Michael–lactonization reactions on 2-(2-nitrovinyl)phenols with alkyl cyclopentanone-2-carboxylates in the presence of a catalytic amount of quinine–NH–thiourea followed by p-TSA.
在催化作用下,邻邻邻羟基引发的2-(2-硝基乙烯基)苯酚与烷基环戊酮-2-羧酸酯的连续迈克尔-内酯化反应,实现了一种具有四级立体中心的高度取代的螺二氢香豆素的不对称合成的一般方法。的数量奎宁– N H–硫脲其次是p -TSA。
Asymmetric Synthesis of 3,4-Dihydrocoumarin Motif with an All-Carbon Quaternary Stereocenter <i>via</i> a Michael–Acetalization Sequence with Bifunctional Amine-thiourea Organocatalysts
作者:Bor-Cherng Hong、Prakash Kotame、Gene-Hsiang Lee
DOI:10.1021/ol202331j
日期:2011.11.4
Asymmetric domino Michael acetalization reactions of 2-hydroxynitrostyrene and 2-oxocyclohexanecarbaldehyde with a bifunctional thioureatertiary-amine organocatalyst, e.g., the Takemoto catalyst, followed by oxidation providing the 1',3-spiro-2'-oxocyclohexan-3,4-dihydrocoumarin having one all-carbon quaternary stereocenter with excellent diastereo- and enantioselectivities (up to >99% ee), are described. The structures and absolute configurations of the products were confirmed by X-ray analysis.