Synthesis of Optically Active (2-Arylvinyl)glycine Derivatives by Palladium-Catalyzed Arylation of (S)-N-(Benzyloxycarbonyl)vinylglycine.
作者:Taisuke ITAYA、Yoshitaka HOZUMI
DOI:10.1248/cpb.46.1094
日期:——
Phenyl, tolyl, anisyl, and 1-naphthyl iodides (7a-g, n) smoothly reacted with (S)-N-(benzyloxycarbonyl)-vinylglycine (6) in H2O in the presence of Pd(OAc)2, Bu4NCl, and NaHCO3 at 45°C, producing [S-(E)]-(2-arylvinyl)glycine derivatives 8a-g, n of high enantiomeric purity. The yields of the reactions of 3- (7f), 2- (7e), and 4-iodoanisoles (7g) increased in this order. This relationship between the yield and the position of substitution has been found to hold for bromophenyl iodides (7i-k), although somewhat lower chemical and optical yields were realized in these cases. Phenyl iodide 7l carrying an electron-withdrawing 4-acetyl group gave an unsatisfactory result, and more electron-deficient 4-nitrophenyl iodide (7m) did not provide the desired product. All these results suggest that the reaction is advantageous with electron-sufficient substrates 7. However, this was not the case for 4-iodophenol (7h), as well as some heterocyclic iodides.
苯基、托基、醚基和1-萘基碘化物(7a-g, n)在Pd(OAc)2、Bu4NCl和NaHCO3存在下,于45°C的水中与(S)-N-(苄氧羰基)-乙烯基甘氨酸(6)发生了顺利反应,生成了具有高对映体纯度的[S-(E)]-(2-芳基乙烯基)甘氨酸衍生物8a-g, n。这三种反应产物的产率按顺序依次为:3-碘化物(7f)、2-碘化物(7e)和4-碘化安息香醚(7g)。这种产率与取代位置之间的关系在溴苯基碘化物(7i-k)中也得到了验证,尽管在这些情况下化学和光学产率稍低。带有电子吸引的4-乙酰基苯碘化物(7l)反应结果不理想,而更具电子缺乏性的4-硝基苯碘化物(7m)未能得到所需产物。所有这些结果表明,该反应对电子充足的底物7是有利的。然而,对4-碘酚(7h)以及某些杂环碘化物来说情况并非如此。