Chiral proton donor reagents: Tin tetrachloride-coordinated optically active binaphthol derivatives
Chiral proton donor reagents: Tin tetrachloride-coordinated optically active binaphthol derivatives
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DOI：
10.1002/tcr.10020
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发表时间：
2002-01-01
期刊：
影响因子：
6.6
通讯作者：
Yamamoto, H
中科院分区：
文献类型：
--
作者：
Ishibashi, H;Ishihara, K;Yamamoto, H
以四氯化锡和旋光性双酚衍生物为原料制备的Lewis酸辅助手性Bronsted酸（chiral LBAs）是一种高效的手性质子供体试剂，可用于对映选择性质子化和仿生多烯环化。这些手性LBAs可以直接将各种硅烯醇醚和烯酮二烯基缩醛质子化，分别得到相应的α -芳基或α -环酮和α -芳基羧酸，对映体过量（高达98% ee）。在四氯化锡的存在下，使用化学计量量的2,6-二甲基苯酚和催化量的光活性双酚的单甲基醚也实现了对映选择性质子化。用手性LBA将简单类异戊二烯仿生环化成多环类异戊二烯。这是合成化学中手性Bronsted酸诱导的对映选择性烯环化的第一个例子。香叶基苯基醚、邻香叶基酚和均根基酚衍生物在(R)双酚衍生物和四氯化锡（高达90% ee）存在下直接环化。含法尼基的化合物也可以在相同的条件下环化，得到天然产物(-)-ambrox(R)和（-）chromazonarol，以及(-)-四环多聚苯乙烯类化合物。这些手性LBAs识别三取代末端烯烃的前手性面，并选择性地在底物上产生碳正离子。(C) 2002日本化学期刊论坛和Wiley期刊公司。
The Lewis acid-assisted chiral Bronsted acids (chiral LBAs), which are prepared from tin tetrachloride and optically active binaphthol derivatives, are highly effective chiral proton donor reagents for enantioselective protonation and biornimetic polyene cyclization. These chiral LBAs can directly protonate various silyl enol ethers and ketene disilyl acetals to give the corresponding alpha-aryl or alpha-halo ketones and alpha-arylcarboxylic acids, respectively, with high enantiomeric excess (up to 98% ee). A catalytic version of enantioselective protonation was also achieved using stoichiometric amounts of 2,6-dimethylphenol and catalytic amounts of monomethyl ether of optically active binaphthol in the presence of tin tetrachloride. The biornimetic cyclization of simple isoprenoids to polycyclic isoprenoids using chiral LBA is also described. This is the first example of a chiral Bronsted acid-induced enantioselective ene cyclization in synthetic chemistry. Geranyl phenyl ethers, o-geranylphenols, and homogeranylphenol derivatives were directly cyclized in the presence of (R)binaphthol derivatives and tin tetrachloride (up to 90% ee). Compounds bearing a farnesyl group could also be cyclized under the same conditions to give the natural products (-)-ambrox(R) and (-)chromazonarol, and (-)-tetracyclic polyprenoids of sedimentary origin. These chiral LBAs recognize the prochiral face of a trisubstitured terminal olefin and site selectively generate carbocations on the substrates. (C) 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.