关于Hisashi Yamamoto的一篇JACS的问题

作者 forestidle: 来源: 小木虫 350 7 举报帖子

大家好，

小弟这些天实在是郁闷，发帖希望有好心的哥们能帮我一下。

最近在做一个全合成工作，需要(S)-1-phenylbut-3-en-1-ol这个片段，本想用Brown的方法来做的。但是，无意间在一篇综述(Catalytic Enantioselective Allylation of Carbonyl Compounds and Imines, Chem. Rev., 2011, 111, 7774–7854)里看到了Yamamoto的方法(5mol%AgTf/S-BINAP作催化剂，THF作为溶剂，-20度反应8小时，88%yield and 96%ee，详见原文献)。咋一看，操作方便，比Brown的方法简单，结果却相当好。于是，我开始重复，结果让我特别沮丧，按其操作，反应转化率总是很低，8h，基本都是原料。然后用10mol%的催化剂，转化率还是不高，ee值很不理想，和文献报道德完全不符。严格的重复了很多次，结果都是一样，搞的我都不知道怎么和老板提这个事。一个半月完成了一个复杂片段，现在却死在这个JACS的方法上，实在是不甘心。情急之下，两天前的晚上就给Yamamoto去了下面的email，至今没有任何回音。

现在不知道该怎么办，难道就换其他方法，此事作罢？实在不爽，特发此贴,请大家指点。若有兄弟姐妹，能在百忙之中帮忙重复一下，小弟当不胜感激！

附：
1. Yamamoto的原文献
Catalytic Asymmetric Allylation of Aldehydes Using a Chiral Silver(I) Complex
Akira Yanagisawa , Hiroshi Nakashima , Atsushi Ishiba , and Hisashi Yamamoto *
School of Engineering, Nagoya University Chikusa, Nagoya 464-01, Japan
J. Am. Chem. Soc., 1996, 118 (19), pp 4723–4724
https://pubs.acs.org/doi/abs/10.1021%2Fja9603315

2. e-mail(有点不礼貌，实在是郁闷之下。。。)
Dear Professor Hisashi Yamamoto,

i am a postdoc in Germany. Currently, I am working on a natural product synthesis. Instead of Brown allylation, I am determined to use your elegant Ag-BINAP catalyzed allylation of benzaldehyde to obtain a key intermediate. But, unfortunately, exactly following your experimental procedure reported in the paper (JACS, 1996, 118, 4723-4724), the reaction had a very poor conversion after 8 hours (ca. 5% conv.). Then I used 10% of catalyst, the reaction could have 70% conv. but the ee is not satisfactory (75% ee, at-20 oC; in your paper, the ee is 79% even at 20 oC). I tried many times on the reaction, but could not find the problem and really frustrated. So, I hope I could get some tips of this reaction from you. Could you give me some advices at your convenience? I really like your work and don't want to switch to other methods.

Note:
AgOTf: Aldrich (glovebox)
S-BINAP: TCI(glovebox)
Benzaldehyde: fresh dist. under Ar
allyl tributyl tin (Alfa): fresh dist. under Ar
I did extraction after quenched with 1N HCl and KF for 30 min and filtration, as there is very much water seems not possible dried with MgSO4 directly.

Sincerely,
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