Alkene Syn Dihydroxylation with Malonoyl Peroxides
摘要:
Cyclopropyl malonoyl peroxide (1), which can be prepared in a single step from the commercially available diacid, is an effective reagent for the dihydroxylation of alkenes. Reaction of 1 with an alkene in the presence of 1 equiv of water at 40 degrees C followed by alkaline hydrolysis leads to the corresponding diol (40-93%). With 1,2-disubstituted alkenes, the reaction proceeds with syn selectivity (3:1 to > 50:1). A mechanism consistent with the experimental findings that is supported by oxygen-labeling studies is proposed.
RadicalcationDiels–Alderreactions by titanium dioxide (TiO2) photocatalysis in lithium perchlorate/nitromethane solution are described. TiO2 photocatalysis promotes reactions between electron-rich dienes and dienophiles, which would otherwise be difficult to accomplish due to electronic mismatching. The reactions are triggered by hole oxidation of the dienophile and are completed by the excited
<i>anti</i>-Markovnikov Hydroamination of Alkenes Catalyzed by a Two-Component Organic Photoredox System: Direct Access to Phenethylamine Derivatives
作者:Tien M. Nguyen、Namita Manohar、David A. Nicewicz
DOI:10.1002/anie.201402443
日期:2014.6.10
Disclosed herein is a general catalytic system for the intermolecular anti‐Markovnikov hydroamination of alkenes. By using an organocatalytic photoredox system, α‐ and β‐substituted styrenes as well as aliphatic alkenes undergo anti‐Markovnikov hydroamination. Heterocyclic amines were also successfully employed as nitrogen nucleophiles, thus providing a direct route to heterocyclic motifs common in
organic compounds with a trifluoromethyl group. A new and facile synthesis of ketones with a trifluoromethyl substituent in the α‐position proceeds through a one‐potphotoredox‐catalyzed trifluoromethylation–oxidation sequence of aromatic alkenes. Dimethyl sulfoxide (DMSO) serves as a key and mild oxidant under these photocatalytic conditions. Furthermore, an iridium photocatalyst, fac[Ir(ppy)3] (ppy=2‐phenylpyridine)
Abstract For understanding the mechanism involved in the Wittigreaction, it is important to know the factors which influence the stability of 1,2-oxaphosphetane intermediates with pentacoordinate phosphorus; in these intermediates, the steric factor plays a predominant role. Studying the Wittigreaction between nonstabilized ylides and different aldehydes, we noted that the stereochemical outcome