Asymmetric and diastereoselective Mannich reactions using hydantoin as a chiral auxiliary
摘要:
The Mannich reaction of titanium enolates of a chiral hydantoin with various aldimines smoothly occurred in good yields and with high anti-diastereoselectivity. The Mannich adducts can be readily cleaved by alcoholysis to afford several beta-amino ester derivatives in good yields and in almost enantiomerically pure form. (C) 2012 Elsevier Ltd. All rights reserved.
Asymmetric and diastereoselective Mannich reactions using hydantoin as a chiral auxiliary
摘要:
The Mannich reaction of titanium enolates of a chiral hydantoin with various aldimines smoothly occurred in good yields and with high anti-diastereoselectivity. The Mannich adducts can be readily cleaved by alcoholysis to afford several beta-amino ester derivatives in good yields and in almost enantiomerically pure form. (C) 2012 Elsevier Ltd. All rights reserved.
A photochemical deracemization of 5-substituted 3-phenylimidazolidine-2,4-diones (hydantoins) is reported (27 examples, 69%-quant., 80–99% ee). The reaction is catalyzed by a chiral diarylketone which displays a two-point hydrogen bonding site. Mechanistic evidence (DFT calculations, radical clock experiments, H/D labeling) suggests the reaction to occur by selective hydrogenatom transfer (HAT). Upon
<i>N</i>
<sup>1</sup>
‐ and
<i>N</i>
<sup>3</sup>
‐Arylations of Hydantoins Employing Diaryliodonium Salts
<i>via</i>
Copper(I) Catalysis at Room Temperature
reported employing diaryliodonium triflates as aryl source using a copper(I) catalyst. The developed protocol is performable at room temperature and easily scalable. The robustness is confirmed with a wide range of substrate studies of both hydantoins and diaryliodonium salts. Sterically complicated ortho‐substituted diaryliodonium salts are also compatible with the reaction protocol.
Treatment of N-(4-nitrophenoxycarbonyl)amino acid amide, which was prepared from amino acid amide and 4-nitrophenyl chloroformate, under weakly basic conditions proceeded to afford the corresponding hydantoin. A direct conversion of amino acid amide into hydantoin without isolation of N-(4-nitophenoxycarbonyl)amino acid amide was also accomplished.
Quantitative Modeling of Bis(pyridine)silver(I) Permanganate Oxidation of Hydantoin Derivatives: Guidelines for Predicting the Site of Oxidation in Complex Substrates
作者:Amanda J. Bischoff、Brandon M. Nelson、Zachary L. Niemeyer、Matthew S. Sigman、Mohammad Movassaghi
DOI:10.1021/jacs.7b09541
日期:2017.11.1
The bis(pyridine)silver(I) permanganate promoted hydroxylation of diketopiperazines has served as a pivotal transformation in the synthesis of complex epipolythiodiketopiperazine alkaloids. This late-stage C–H oxidation chemistry is strategically critical to access N-acyl iminium ion intermediates necessary for nucleophilic thiolation of advanced diketopiperazines en route to potent epipolythiodiketopiperazine
Multifaceted View on the Mechanism of a Photochemical Deracemization Reaction
作者:Roger Jan Kutta、Johannes Großkopf、Nils van Staalduinen、Antonia Seitz、Philipp Pracht、Stefan Breitenlechner、Christoph Bannwarth、Patrick Nuernberger、Thorsten Bach
DOI:10.1021/jacs.2c11265
日期:2023.2.1
corroborated by nuclearmagneticresonance titration that the catalyst binds the two enantiomers by two-point hydrogenbonding. In one of the diastereomeric complexes, the hydrogenatom at the stereogenic carbon atom is ideally positioned for hydrogenatom transfer (HAT) to the photoexcited benzophenone. Detection of the protonated ketyl radical by transient absorption revealed hydrogen abstraction to