Despite a well-developed and growing body of work in copper catalysis, the potential of copper to serve as a photocatalyst remains underexplored. Herein, we describe a photoinduced, copper-catalyzed method for coupling readily available racemic tertiary alkyl chloride electrophiles with amines to generate fully substituted stereocenters with high enantioselectivity. The reaction proceeds at –40 °C under excitation by a blue light-emitting diode and benefits from the use of a single, Earth-abundant transition metal acting as both the photocatalyst and the source of asymmetric induction. An enantioconvergent mechanism transforms the racemic starting material into a single product enantiomer.
A family of homeotypic porous lanthanide metal−organic frameworks (MOFs), [Ln(btc)(H2O)]·guest (Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Ho (6), Er (7), and Yb (8); guest: DMF or H2O) was synthesized. The structures of the as-synthesized compounds are tetragonal and contain 1D channels with accessible lanthanide ions. In situ single crystal X-ray diffraction shows that 1 undergoes a single-crystal to polycrystalline to single-crystal transformation from room temperature to 180 °C. During the release of DMF and water molecules from the channels by evacuation and subsequent heating, the structures of 1 and 7 transformed from tetragonal to monoclinic, and then to tetragonal, while the structure of 8 remained tetragonal. The transformation between the monoclinic and the low temperature tetragonal phases is reversible. The Ln(btc) MOFs are stable to at least 480 °C and are among the most thermally stable MOFs. The Ln(btc) MOFs act as efficient Lewis acid catalysts for the cyanosilylation of aldehydes yielding cyanohydrins in high yields within short reaction times. 1 also catalyzes the cyanosilylation of less reactive substrates, such as ketones at room temperature. The Ln(btc) MOFs could be recycled and reused without loss of their crystallinity and activity.
A ruthenium trichloride complex has been loaded into an aluminium metal-organic framework (MOF), MOF-253, by post-synthetic modification to give MOF-253-Ru. MOF-253 contains open bipyridine sites that are available to bind with the ruthenium complex. MOF-253-Ru was characterised by elemental analysis, N(2) sorption and X-ray powder diffraction. This is the first time that a Ru complex has been coordinated to a MOF through post-synthetic modification and used as a heterogeneous catalyst. MOF-253-Ru catalysed the oxidation of primary and secondary alcohols, including allylic alcohols, with PhI(OAc)(2) as the oxidant under very mild reaction conditions (ambient temperature to 40 °C). High conversions (up to >99%) were achieved in short reaction times (1-3 h) by using low catalyst loadings (0.5 mol% Ru). In addition, high selectivities (>90%) for aldehydes were obtained at room temperature. MOF-253-Ru can be recycled up to six times with only a moderate decrease in substrate conversion.
A series of new iridium(III) complexes containing bidentate N‐heterocyclic carbenes (NHC) functionalized with an alcohol or ether group (NHCOR, R=H, Me) were prepared. The complexes catalyzed the alkylation of anilines with alcohols as latent electrophiles. In particular, biscationic IrIII complexes of the type [Cp*(NHC‐OH)Ir(MeCN)]2+2[BF4−] afforded higher‐order amine products with very high efficiency; up to >99 % yield using a 1:1 ratio of reactants and 1–2.5 mol % of Ir, in short reaction times (2–16 h) and under base‐free conditions. Quantitative yields were also obtained at 50 °C, although longer reaction times (48–60 h) were needed. A large variety of aromatic amines have been alkylated with primary and secondary alcohols. The reactivity of structurally related iridium(III) complexes was also compared to obtain insights into the mechanism and into the structure of possible catalytic intermediates. The IrIII complexes were stable towards oxygen and moisture, and were characterized by NMR, HRMS, single‐crystal X‐ray diffraction, and elemental analyses.
Allylic alcohols can be isomerised into carbonyl compounds by transition metal complexes. In the last few years, catalyst design and development have resulted in highly efficient isomerisations under mild reaction conditions, including enantioselective versions. In addition, the isomerisation of allylic alcohols has been combined with C-C bond forming reactions when electrophiles such as aldehydes or imines were present in the reaction mixture. Also, C-F bonds can be formed when electrophilic fluorinating reagents are used. Thus, allylic alcohols can be treated as latent enol(ate)s. In this article, we highlight the latest developments concerning the isomerisation of allylic alcohols into carbonyl compounds, focusing in particular on tandem isomerisation/C-C or C-heteroatom bond formation processes. Significant attention is given to the mechanistic aspects of the reactions.
The mechanism of the N-alkylation of amines with alcohols catalyzed by an iridium complex containing an Nheterocyclic carbene (NHC) ligand with a tethered alcohol/alkoxide functionality was investigated by a combination of experimental and computational methods. The catalyst resting state is an iridium−hydride species containing the amine substrate as a ligand, and decoordination of the amine, followed by coordination of the imine intermediate to the iridium center, constitute the rate-determining step (rds) of the catalytic process. The alcohol/alkoxide that is tethered to the NHC participates in every step of the catalytic cycle by accepting or releasing protons and forming hydrogen bonds with the reacting species. Thus, the iridium complex with the alcohol/alkoxide tethered to the N-heterocyclic carbene ligand acts as a bifunctional catalyst.
The preparation of chiral alcohols and amines by using iridium catalysis is reviewed. The methods presented include the reduction of ketones or imines by using hydrogen (hydrogenations), isopropanol, formic acid, or formate (transfer hydrogenations). Also dynamic and oxidative kinetic resolutions leading to chiral alcohols and amines are included. Selected literature reports from early contributions to December 2012 are discussed.
HR-MS: m/z 287.9878 ([M+H] + , C10H11INO + calcd. 287.9885). 3-Iodo-1-(4-methoxyphenyl)pyrrolidin-2-one. The title compound was prepared according to Method B from 2,4-dibromobutyryl chloride and p-anisidine. After purification by flash chromatography (30→70% Et2O in hexanes), the title compound was isolated as a white solid in 48% yield over 2 steps.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.