Chiral squaramide derivatives are excellent hydrogen bond donor catalysts.
Chiral squaramide derivatives are excellent hydrogen bond donor catalysts.
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DOI：
10.1021/ja805693p
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发表时间：
2008-11-05
影响因子：
15
通讯作者：
Rawal, Viresh H.
中科院分区：
文献类型：
--
作者：
Malerich, Jeremiah P.;Hagihara, Koji;Rawal, Viresh H.
硫脲代表氢键促进的不对称催化剂的主要平台。大量的反应，在几十个出版物中报道，已经成功地促进了手性硫脲。本文报道了方酰胺作为一种高效的新型骨架用于手性氢键给体催化剂的开发。方酰胺催化剂制备非常简单。由方酸甲酯经两步反应制得的（-）-辛可宁改性方酰胺（5），即使在催化剂负载量低至0.1mol%时，也能有效地催化1，3-二羰基化合物与β-硝基苯乙烯的共轭加成反应。加成产物以高收率和优异的对映选择性得到。
Thioureas represent the dominant platform for hydrogen bond promoted asymmetric catalysts. A large number of reactions, reported in scores of publications, have been successfully promoted by chiral thioureas. The present paper reports the use of squaramides as a highly effective new scaffold for the development of chiral hydrogen bond donor catalysts. squaramide catalysts are very simple to prepare. The (-)-cinchonine modified squaramide (5), easily prepared through a two step process from methyl squarate, was shown to be an effective catalyst, even at catalyst loadings as low as 0.1 mol%, for the conjugate addition reactions of 1,3-dicarbonyl compounds to β-nitrostyrenes. The addition products were obtained in high yields and excellent enantioselectivities.
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