Asymmetric hydroalkoxylation of non-activated alkenes: titanium-catalyzed cycloisomerization of allylphenols at high temperatures.
Asymmetric hydroalkoxylation of non-activated alkenes: titanium-catalyzed cycloisomerization of allylphenols at high temperatures.
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DOI：
10.1002/anie.201409252
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发表时间：
2015-03
影响因子：
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通讯作者：
J. Schlüter;Max Blazejak;F. Boeck;Lukas Hintermann
中科院分区：
文献类型：
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作者：
J. Schlüter;Max Blazejak;F. Boeck;Lukas Hintermann
通过2-烯丙基苯酚环异构化为2-甲基-2,3-二氢苯并呋喃（2-甲基香豆素），实现了醇（酚）与非活化烯烃的不对称催化加成。该反应由手性钛-羧酸盐配合物在异常高温下催化不对称催化反应。该催化剂是通过将异丙醇钛、手性配体(aS)-1-(2-甲氧基-1-萘基)-2-萘甲酸或其衍生物和助催化量的水以1:1:1的比例(各5mol％)混合而产生的。这种均相热催化 (HOT-CAT) 产生了各种 (S)-2-甲基香豆素，其产率高达 90%，在 240 °C 时的 ee 高达 85%，在 220 °C 时的 ee 高达 87%。
The asymmetric catalytic addition of alcohols (phenols) to non-activated alkenes has been realized through the cycloisomerization of 2-allylphenols to 2-methyl-2,3-dihydrobenzofurans (2-methylcoumarans). The reaction was catalyzed by a chiral titanium-carboxylate complex at uncommonly high temperatures for asymmetric catalytic reactions. The catalyst was generated by mixing titanium isopropoxide, the chiral ligand (aS)-1-(2-methoxy-1-naphthyl)-2-naphthoic acid or its derivatives, and a co-catalytic amount of water in a ratio of 1:1:1 (5 mol % each). This homogeneous thermal catalysis (HOT-CAT) gave various (S)-2-methylcoumarans with yields of up to 90 % and in up to 85 % ee at 240 °C, and in 87 % ee at 220 °C.