Catalytic Generation of Donor-Acceptor Cyclopropanes under <i>N</i>
-Heterocyclic Carbene Activation and their Stereoselective Reaction with Alkylideneoxindoles
作者:Liher Prieto、Eduardo Sánchez-Díez、Uxue Uria、Efraím Reyes、Luisa Carrillo、Jose L. Vicario
DOI:10.1002/adsc.201700198
日期:2017.5.17
Formylcyclopropanes undergo activation in the presence of an N‐heterocyclic carbene catalyst generating a donor‐acceptorcyclopropane intermediate with the ability to undergo ring‐opening followed by formal [4+2] cycloaddition with alkylideneoxindoles. This enables the direct enantio‐ and diastereoselective synthesis of tetrahydropyrano[2,3‐b]indoles through the use of a chiral NHC catalyst.
甲酰基环丙烷在N杂环卡宾催化剂的存在下发生活化,生成供体-受体环丙烷中间体,该中间体具有开环能力,然后与亚烷基亚氧吲哚进行正式的[4 + 2]环加成反应。这样可以通过使用手性NHC催化剂直接对映和非对映选择性合成四氢吡喃并[2,3- b ]吲哚。
Highly Enantioselective Synthesis of 3,4-Dihydropyrans through a Phosphine-Catalyzed [4+2] Annulation of Allenones and β,γ-Unsaturated α-Keto Esters
作者:Weijun Yao、Xiaowei Dou、Yixin Lu
DOI:10.1021/ja5109358
日期:2015.1.14
A phosphine-catalyzed novel [4+2] annulation process was devised employing allene ketones as C2 synthons and β,γ-unsaturated α-keto esters as C4 synthons. In the presence of an L-threonine-derived bifunctional phosphine, 3,4-dihydropyrans were obtained in high yields and with virtually perfect enantioselectivities. The synthetic value of the dihydropyran motif was demonstrated by a concise preparation
Highly Enantioselective Michael Addition of α-Substituted Cyano Ketones to β,γ-Unsaturated α-Keto Esters using Bifunctional Thiourea-Tertiary Amine Catalysts: An Easy Access to Chiral Dihydropyrans
An asymmetric Michaeladdition of α-substituted cyano ketones to β,γ-unsaturated α-keto esters to form chiral dihydropyrans catalyzed by a series of α-amino acid-derived thiourea-tertiary amines is presented. A novel tyrosine-derived thiourea catalyst was identified as the optimal catalyst providing the desired product in 91–95% yields and with 90–96% ee at a low catalyst loading of 2.0 mol%. The utility
Bi(OAc)<sub>3</sub>/Chiral Phosphoric Acid-Catalyzed Enantioselective 1,2- and Formal 1,4-Allylation Reaction of β,γ-Unsaturated α-Ketoesters
作者:Xiang-Shuai Liu、Yao Li、Xin Li
DOI:10.1021/acs.orglett.1c03453
日期:2021.12.3
highly efficient asymmetric 1,2-allylation reaction of β,γ-unsaturatedα-ketoesters was realized by using a Bi(OAc)3/chiral phosphoric acid catalyst system under mild conditions. Meanwhile, using this combined strategy of enantioselective 1,2-allylation and subsequent anionic oxy-Cope rearrangement, the asymmetric formal 1,4-allylation reaction was achieved by a one-pot process. These reactions offer