Isolation of methyl (
<i>RS</i>
)‐1‐
<i>tert</i>
‐butoxycarbonyl‐3‐cyanomethyl‐1,2‐dihydro‐2‐oxo‐5
<i>H</i>
‐pyrrole‐5‐carboxylate, the key‐intermediate in base‐catalyzed formation of racemic products by 1,3‐dipolar cycloadditions to methyl (
<i>S</i>
)‐1‐
<i>tert</i>
‐butoxycarbonyl‐3‐[(
<i>E</i>
)‐cyanomethylidene]‐2‐pyrrolidinone‐5‐carboxylate
作者:Marko Škof、Samo Pirc、Simon Rečnik、Jurij Svete、Branko Stanovnik、Ljubo Golič、Lovro Selič
DOI:10.1002/jhet.5570390516
日期:2002.9
Cycloadditions of various 1,3-dipoles to methyl (S)-1-tert-butoxycarbonyl-3-[(E)-cyanomethylidene]-2-pyrrolidinone-5-carboxylate (9) were studied. Reactions of 9 with diazomethane (10) and 2,4,6-trimethoxy-benzonitrile oxide (11), carried out under neutral conditions, gave the corresponding optically active spiro compounds 16-18 with low diastereoselectivity (20-30% diastereomeric excess). On the other
研究了各种1,3-偶极与(S)-1-叔丁氧基羰基-3-[(E)-氰基亚甲基] -2-吡咯烷酮5-羧酸甲酯(9)的环加成反应。的反应9用重氮甲烷(10)和2,4,6-三甲氧基-苄腈氧化物(11),在中性条件下进行,得到相应的光学活性的螺环化合物16-18具有低非对映选择性(20-30%非对映体过量) 。另一方面,9与一氧化二氮11和腈亚胺14、15的反应在碱的存在下进行,得到82-86%非对映异构体过量的外消旋吡唑和异恶唑稠合的2-吡咯烷酮21-23。在碱性氧化铝的存在下将旋光性双极性亲和剂9异构化,得到(RS)-1-叔丁氧基-羰基-3-氰基甲基-1,2-二氢-2-氧代-5 H-吡咯-5-羧酸酯(19)。用偶极子11和14处理外消旋偶极子19,得到融合的2-吡咯烷酮23和21。这些观察结果支持化合物19如外消旋cycloadducts 21-形成的关键中间体23。