Novel bifunctional thiourea–ammonium salt catalysts derived from amino acids: application to highly enantio- and diastereoselective aza-Henry reaction
作者:Hong-Yu Wang、Zhuo Chai、Gang Zhao
DOI:10.1016/j.tet.2013.04.079
日期:2013.6
development of new efficient and easily accessible catalysts has been one of the focuses in asymmetric phase-transfer catalysis. In this paper, a novel class of chiral bifunctional thiourea–ammonium phase-transfercatalysts were synthesized from commercially available α-amino acids. The structural modularity of these catalysts permits facile tunings to achieve optimum results, which was demonstrated
catalytic enantio- and diastereoselective nitro-Mannichreaction of α-amido sulfones in the mixed solvent of toluene/H2O has been realized using a phase-transfer catalyst (PTC) derived from cinchona alkaloids and N-benzotriazole. It performed well over a wide range of substrates to give the desired products in good yields (up to 94%) with excellent enantioselectivities (up to 99% ee) and diastereoselectivities
使用衍生自金鸡纳生物碱和N-苯并三唑的相转移催化剂(PTC)实现了α-酰胺基砜在甲苯/ H 2 O混合溶剂中的催化对映体和非对映体的硝基曼尼希反应。它在各种底物上均表现良好,以高收率(最高94%)提供所需的产品,并具有出色的对映选择性(最高99%ee)和非对映选择性(最高99:1)。
Asymmetric Hydroazidation of Nitroalkenes Promoted by a Secondary Amine-Thiourea Catalyst
作者:Tiziana Bellavista、Sara Meninno、Alessandra Lattanzi、Giorgio Della Sala
DOI:10.1002/adsc.201500403
日期:2015.10.12
Chiral β-nitro azides are obtained by asymmetric addition of azides to nitroalkenes, with an enantioselectivity of up to 82% ee. The reaction, promoted by an easily accessible secondaryamine-thioureacatalyst, is performed with azidotrimethylsilane in the presence of benzoic acid. Products with different aliphatic β-substituents are obtained in good yields and with the highest enantioselectivity reported
Bifunctional asymmetric phase-transfercatalysts bearing multiple hydrogen-bonding donors have rarely been explored. The first quaternary ammonium type of these catalysts derived from cinchona alkaloids were readily prepared and found to be highly efficient catalysts for asymmetric nitro-Mannichreactions of amidosulfones. Compared with previous reports, very broad substrate generality was observed
New chiral bifunctional thiourea-phosphonium salts have been developed based on natural amino acids as highly efficient phase-transfer catalysts in the enantioselectiveaza-Henryreaction.