A general, metal‐free, highly enantioselective Brønsted acidcatalyzed [3+2] cycloaddition between hydrazones and alkenes has been developed that affords pyrazolidinederivatives (see scheme). The resulting optically active pyrazolidines can undergo many chemical transformations which allow, for example, the enantioselective synthesis of valuable pyrazolines and 1,3‐diamines.
Asymmetric Organocatalyzed Aza‐Henry Reaction of Hydrazones: Experimental and Computational Studies
作者:Isaac G. Sonsona、Juan V. Alegre‐Requena、Eugenia Marqués‐López、M. Concepción Gimeno、Raquel P. Herrera
DOI:10.1002/chem.202000232
日期:2020.4.24
which the control of chirality is vital, such as the pharmaceutical industry. Additionally, experimental and ab initio studies were performed to understand the reaction mechanism. The experimental results revealed an unexpected secondary kinetic isotope effect (KIE) that is explained by the calculated reaction pathway, which shows that the protonation of the initial hydrazone and the C-C bond forming reaction
Combining<i>in situ</i>Generated Chiral Silicon Lewis Acid and Chiral Brønsted Acid Catalysts for [3+2] Cycloadditions: Cooperative Catalysis as a Convenient Enantioselective Route to Pyrazolidines
作者:Olga V. Serdyuk、Alexandru Zamfir、Frank Hampel、Svetlana B. Tsogoeva
DOI:10.1002/adsc.201200293
日期:2012.11.12
A facile enantioselective synthesis of chiral pyrazolidines via a [3+2] cycloadditionreaction, involving a BINOL-derived phosphoric acid and an in situ generated BINOL phosphate-derived siliconLewisacid, which may act cooperatively, has been developed.
Silicon Lewis Acid Catalyzed [3+2] Cycloaddition Reactions of Hydrazones/Cyclopentadiene: Mild Access to Pyrazolidine Derivatives
作者:Alexandru Zamfir、Sebastian Schenker、Walter Bauer、Timothy Clark、Svetlana B. Tsogoeva
DOI:10.1002/ejoc.201100206
日期:2011.7
A first and fairly mild metal-free catalytic route was developed for the [3+2] cycloadditions of different N-acylhydrazones to cyclopentadiene, providing the synthetically andbiologically important five-membered cyclic compounds pyrazolidines. The reaction was successfully conducted in high yields (up to 99 %) with high diastereoselectivities (up to 98:2 dr) by using catalytic amounts of TMSOTf (trimethylsilyl
Asymmetric Hydrocyanation of Hydrazones Catalyzed by in Situ Formed <i>O</i>-Silylated BINOL-Phosphate: A Convenient Access to Versatile α-Hydrazino Acids
作者:Alexandru Zamfir、Svetlana B. Tsogoeva
DOI:10.1021/ol9025974
日期:2010.1.1
A first organocatalytic enantioselective route was developed for the conversion of readily prepared and air stable aliphatic hydrazones to synthetically valuable alpha-hydrazinonitriles. This BINOL-phosphate catalyzed Strecker-type reaction (see scheme, Ar = p-NO2-Ph) provides a new practical and direct route to alpha-hydrazino acids of synthetic and biological importance. The actually active catalyst is proposed to be an In situ formed O-silylated BINOL-phosphate, thus shifting the nature of catalysis from Bronsted acid to Lewis acid organocatalysis.