: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Complete Field Guide to Asymmetric BINOL-Phosphate Derived Brønsted Acid and Metal Catalysis: History and Classification by Mode of Activation; Brønsted Acidity, Hydrogen Bonding, Ion Pairing, and Metal Phosphates

Iron Catalysis in Organic Synthesis

Department of Chemistry, Tianjin University, Tianjin 300072, China; Department of Applied Chemistry, China Agricultural University, Beijing 100193, China; UMR 6014 CNRS, Laboratoire COBRA de l’IRCOF, Université et INSA de Rouen, Rue Tesniere, F-76130 Mont Saint Aignan, France; and Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Science, Shanghai 200032, China

Asymmetric construction of stereogenic carbon centers featuring a trifluoromethyl group from prochiral trifluoromethylated substrates.

The effective use of ring strain has been applied to considerable advantage for the construction of complex systems. The focus here is directed towards cyclopropanes as building blocks for organic synthesis. Although thermodynamics should take the side of synthetic chemists, only a specific substitution pattern at the cyclopropane ring allows for particularly mild, efficient, and selective transformations. The required decrease in the activation barrier is achieved by the combined effects of vicinal electron-donating and electron-accepting moieties. This Review highlights the appropriate tools for successfully employing donor–acceptor cyclopropanes in ring-opening reactions, cycloadditions, and rearrangements.

A new golden age for donor-acceptor cyclopropanes.

A highly diastereo- and enantioselective BOX/Cu(II)-catalyzed C2,C3-cyclopentannulation of indoles with donor–acceptor cyclopropanes has been developed on the basis of asymmetric formal [3 + 2] cycloaddition of indoles. This reaction provides rapid and facile access to a series of enantioenriched cyclopenta-fused indoline products and can be further extended to the construction of tetracyclic pyrroloindolines. The synthetic potential of the reaction was demonstrated in a four-step synthesis of the core structure of borreverine.

Copper-catalyzed highly enantioselective cyclopentannulation of indoles with donor-acceptor cyclopropanes.

ConspectusIn asymmetric catalysis, the remote control of enantioselection is usually difficult due to the long distance communication between the chiral center of the catalyst and the reactive site of the substrate. The development of efficient and highly enantioselective catalysts for such reactions is of great importance and highly desirable. The stereocontrol over an asymmetric reaction is a delicate process (ca. 3.0 kcal/mol difference in transition states can lead to >99/1 enantiomeric selectivity at room temperature), it therefore requires fine-tuning on the electronic nature of the central metal together with a precisely created cavity to accommodate the substrates and reagents. We envision that a solution is the design of new catalysts by finding an easy and efficient way to tune the electronic properties, the chiral space, and the shape of the catalytic site. Since an extra coordination group in the organometallic complex could not only alter the microenvironment around the metal center in a thre...

Side arm strategy for catalyst design: modifying bisoxazolines for remote control of enantioselection and related.

Confined chiral Bronsted acids are shown to catalyze asymmetric oxidations of sulfides to sulfoxides with hydrogen peroxide. The wide generality and high enantioselectivity of the developed method compare even to the best metal-based systems and suggest utility in other asymmetric oxidations.

Activation of H2O2 by Chiral Confined Brønsted Acids: A Highly Enantioselective Catalytic Sulfoxidation

Inspired by pioneering contributions on chiral Bronsted acid mediated reactions and our own studies in aminocatalysis, we are currently exploring asymmetric counteranion-directed catalysis (ACDC) as a general strategy for asymmetric synthesis. According to this concept, catalytic reactions that proceed via cationic intermediates can be performed highly enantioselectively by the incorporation of a chiral counteranion into the catalyst. After our initial proof of concept with organocatalytic transfer hydrogenations and epoxidations, ACDC has recently been extended to transition-metal catalysis with Toste s gold-catalyzed allene cyclizations, and our palladium-catalyzed Tsuji–Trost-type a-allylation of aldehydes. The further exploration of the potential of ACDC in transition-metal catalysis, especially applied to redox reactions, is of great interest and significance. Here we report a highly enantioselective epoxidation of olefins that is catalyzed by a chiral ion pair consisting of an achiral Mn–salen cation and a chiral phosphate counteranion. Stimulated by an important contribution from Kochi et al. , Jacobsen and Katsuki have significantly advanced the catalytic asymmetric epoxidation of unfunctionalized alkenes by introducing chiral Mn–salen catalysts. These complexes display a broad substrate scope although certain olefin classes still fail to be converted with high enantioselectivity. Interestingly, cationic Mn–salen complexes are C2-symmetrical and inherently chiral—even when the salen ligand itself is achiral. In case of the Jacobsen–Kastuki epoxidation, the chiral backbone of the salen ligand fixes the complex in one of the two enantiomorphic confirmations. The neutral donor ligands typically added increase reactivity and enantioselectivity by displacing the apically coordinated anion of the Mn complex. Chiral neutral donor ligands such as sparteine and chiral N-oxides have been used in combination with an achiral Mn–salen complex and shown to shift the equilibrium of enantiomeric conformational isomers of the cationic metal complex to one side. Reasonably good enantioselectivities have been achieved in the corresponding epoxidations. We hypothesized that a chiral counteranion should also be able to induce a preference for one of the two enantiomorphic conformations. Specifically, chiral binol-derived phosphate anions are ideally suited for our purposes, because in addition to possibly inducing one enantiomorphic conformation of the cationic complex, these ions may also amplify the chiral microenvironment around the metal center with suitable substituents at the 3,3’-positions (Figure 1). Overall, this may lead to a new type of chiral Mn–salen catalyst with unique properties.

Asymmetric Counteranion‐Directed Transition‐Metal Catalysis: Enantioselective Epoxidation of Alkenes with Manganese(III) Salen Phosphate Complexes

An efficient [4 + 3] cycloaddition reaction of D–A cyclopropanes with dienes has been successfully developed. The reaction proceeds well with various dienolsilyl ethers in the presence of Lewis acid, delivering a variety of cycloheptenes and [n,5,0]carbobicycles with excellent stereoselectivity. The asymmetric version of this reaction is also realized using a newly designed chiral Cy-TOX ligand, providing a new approach to access optically active cycloheptenes and [n,5,0]carbobicycles. Mechanisic study reveals that the reaction involves a stepwise pathway, which undergoes an unusual ring opening of five-membered [3 + 2] intermediate and sequential intramolecular cyclization to afford the thermodynamically stable [4 + 3] annulation product.

Saihu Liao

Papers

Copper-catalyzed highly enantioselective cyclopentannulation of indoles with donor-acceptor cyclopropanes.

Side arm strategy for catalyst design: modifying bisoxazolines for remote control of enantioselection and related.

Activation of H2O2 by Chiral Confined Brønsted Acids: A Highly Enantioselective Catalytic Sulfoxidation

Asymmetric Counteranion‐Directed Transition‐Metal Catalysis: Enantioselective Epoxidation of Alkenes with Manganese(III) Salen Phosphate Complexes

Asymmetric Annulation of Donor–Acceptor Cyclopropanes with Dienes