Chiral Dienophiles Derived from Malic Acid: Synthesis of (Z)-(2S)-(tert-Butyl)-5-(ethoxycarbonylmethylene)-1,3-dioxolan-4-one and Its Diels-Alder Reaction with Cyclopentadiene
摘要:
本文描述了标题手性烯烃 12 的合成过程。通过 X 射线分析确定了其结构。12 与环戊二烯的 Diels-Alder 反应只产生外向产物,面选择性高达 95%。
Chiral Dienophiles Derived from Malic Acid: Synthesis of (Z)-(2S)-(tert-Butyl)-5-(ethoxycarbonylmethylene)-1,3-dioxolan-4-one and Its Diels-Alder Reaction with Cyclopentadiene
摘要:
本文描述了标题手性烯烃 12 的合成过程。通过 X 射线分析确定了其结构。12 与环戊二烯的 Diels-Alder 反应只产生外向产物,面选择性高达 95%。
Asymmetric radical additions using chiral 1,3-dioxolane-4-ones
作者:Georg Kneer、Jochen Mattay
DOI:10.1016/s0040-4039(00)74714-9
日期:1992.12
selectivities are observed in additions of alkyl radicals to the chiral (c,d) olefin (2S)-2-tert-butyl-5-ethoxycarbonylmethylene-1,3-dioxolane-4-one1. The following hydrogen abstraction from tributylstannane proceeds with excellent asymmetric stereocontrol, leading to two of four possible diastereoisomers with high diastereomeric excesses. Additions of chiral radicals obtained from (2R,5R)-5-alkyl-5-bromo-1
The hydrogen abstraction of radical intermediates yielded by radical addition to the methylene compound 6, shows excellent facial selectivity. Conformational analyses of the radical intermediates were carried out by quantum chemical calculations and explain these results. The chiral radicals 7 and 8, yielded from the chiral bromides 3 and 4, lead with ethyl acrylate to the adducts 28 and 29 with more 96 % de. The adduct 28 was converted to the optically active gamma-valerolactone 30. The structures of the bromides 3, 4 and 31 as well as the radical adducts 19a, 24 and 25 have been verified by X-ray diffraction analysis.
KNEER, GEORG;MATTAY, JOCHEN;RAABE, GEORHARD;KRUGER, CARL;LAUTERWEIN, JURG+, SYNTHESIS,(1990) N, C. 599-603